PREAMBLE OF INVENTION :- This invention in particular describes the nature of the invention and the manner in which it is to be performed.

FIELD OF INVENTION :- The present embodiment relates generally to the audio recording, mixing and playback and more particularly to system for recording standardized soundtrack level in cinemas and other venues.

BACKGROUND OF THE INVENTION:

Today cinema soundtracks are played back at different levels of loudness in different cinemas. Ideally, soundtracks should be played back at the same level as they were mixed in the studios. However, due to multiple problems faced by various operators in the recording and playback chain, there is no consistency of playback levels of soundtracks. The various problems faced are as follows: i) There is no consistency of recording levels of films, trailers and commercials.

Some are recorded too loud, some are recorded soft. Some have extremely loud sequences.

Current action - the projectionist sets the playback level in cinemas as per his personal judgment, rather than following a playback standard. Projectionists are not trained audio engineers and the experience intended by the film maker is lost. ii) Advertisements and Commercials are recorded too loud as the recording engineers keep fighting for relative loudness between ads.

Current action - the projectionists reduce playback level as per the commercials, and the movie that follows remains at that level, and the intended impact is lost. iii) Certain studios and engineers believe that their soundtracks will be played back at lower levels in cinemas, and record even louder. Current Action- the projectionists reduce playback level even further. Any other content playing along with this is also played at this further reduced level. iv) Certain films are recorded with excessive dynamic range. The loud action sequences or music sequences are recorded too loud. Earlier, Dolby SR. soundtracks had limited dynamic range. Hence playback levels were more consistent.

Current action - the projectionists reduce the playback level of the entire film to suit these loud-sections. The rest of the film plays back at a reduced level and the intended impact is lost. v) Some Film-makers record louder than what the audience wants to hear. Mixing Engineers are exposed to loud sound round the clock and have a tendency to push up levels. Film director are also very excited about their film and prefer loud soundtracks. However, audiences in cinemas do. not wish to hear at such loud levels and complain to the cinema manager.

Current action - the projectionists reduce the playback level. vi) Regional and cultural differences - People in different countries and localities perceive different loudness and wish to hear differently. For ex, people in Germany prefer to hear much softer than people in South India. Even within the same country, people in large cities are continuously exposed to loud sounds compared to people living in small quiet towns. As a result, the perception of loudness also changes.

Current action - the projectionist change playback levels to suit the local needs, thereby defeating the existence of a global playback standard. vii) The recommended playback level for cinemas is 7. However, over the last decade, projectionists have been receiving content at inconsistent levels and have been setting their own levels. New projectionists who have joined in the last couple of years have always seen content being played back at 5 or 6 and are not even aware that the recommended playback level is 7.

Current action - Even when a film is mixed at proper levels and can be played back at 7, it normally gets played back at 5 or 6 as projectionists are not even aware of the recommended playback level of 7. viii) Some cinemas have under-powered systems installed. As a result, the system goes into distortion or amplifiers go into clipping during loud sections in a soundtrack. Sometimes under-powered speakers are also blown by these loud sections.

Current action - the projectionists reduce playback level when they see amplifiers going to clipping or even prior to that to avoid speakers from blowing. ix) Improper calibration of cinemas by un-trained engineers

Current action - this affects the perceived loudness and hence the projectionist has to change the playback level, thereby defeating the existence of a global play back standard. x) Improper calibration of cinemas due to improper tools used by engineers - normally cinema audio systems are aligned using real time analyzers. These analyzers need to be re-calibrated on a periodic basis. Engineers tend to ignore this and keep using these for years without calibration.

Current action - this affects the perceived loudness and hence the projectionist has to change the playback level to compensate, thereby defeating the existence of a global playback standard. xi) Speaker response in certain microphone positions in cinemas might show bumps and dips on the real time analyzer. This results in incorrect SPL readings on the real time analyzer. Many engineers do not understand this while calibrating the cinema audio system and end up calibrating the system incorrectly.

Current action - this affects the perceived loudness and hence the projectionist has to change the playback level to compensate, thereby defeating the existence of a global playback standard. xii) Currently cinema speakers are calibrated to the X curve. This X curve was designed in the 1980s for large cinemas. Now cinemas are much smaller and the X curve is not valid for these small rooms. Though there are recommendations on variations of the X curve for small rooms, this is left upto the subjective judgement of the installer leading to inconsistent results. Current action - this affects the perceived loudness in small rooms and hence the projectionist has to change the playback level to compensate. These days, the recording studios are mostly small rooms. Variation in the alignment of the studio results in improper playback of soundtracks in all cinemas.

One of the prior art means is disclosed in patent no.WO0141452. A technique for identifying inconsistencies between duplicate digital videos, which involves in particular the sample by sample comparison of the audio track of an original video and the audio track of a duplicate video and the generation of a log file indicating the differences between the tracks.

The patent application No. US 4,455,634 disclose another method for controlling a two-channel audio recording, by comparing corresponding amplitudes of both channels.

Another one prior art means is disclosed in US patent no. 5450146.This patent discloses high fidelity reproduction device for cinema sound. In this patent, system for recording soundtracks on a disk is disclosed which is called as DTS and is on its way out with 35mm.Problems relating to splices in the film are solved by reading the sound in advance, in storing it in a memory, in reading it back subsequently from the memory, and, where necessary, in causing the memory read back system to jump in order to avoid reproducing sound that corresponds to images that have been removed from the film.

Earlier Attempts at controlling loudness in Cinemas

Maximum LEQ levels have been specified for trailers and commercials. No maximum LEQ level have been specified for feature films. It is difficult to fix one maximum LEQ level for all trailers in the world. Trailers and films are made differently in different parts of the world. An action trailer mixed at 85 LEQ might sound fine, but a dialogue based trailer mixed at 85 LEQ may sound very loud. The perceived loudness also depends on the picture. If the trailer has continuous action from first frame to last frame, it might not appear to be very loud. However the measured LEQ may exceed 85. Bringing the master level down to read a LEQ of 85 may make the trailer sound 'weak'.

It is difficult to control loudness using a metering system which measures only audio, and is blind to the visuals. Therefore, there is a need for such a system which will solve sound loudness problem on the digital platform.

Disadvantages of prior art are as follows.

1) Improper playback of soundtracks in all cinemas.

2) Consistency is not maintained in recording levels of films, trailers and commercials.

3) Consistency is not maintained in playback levels in cinemas.

The advantages of the present embodiment are as follows.

1) A hassle free system for playback of movies in cinemas for maintaining loudness level of the surround sound format.

2) Automatic compensation of target speaker response as per room size.

3) Quality control and management of cinema equipment installers, mastering engineers, recording studios and cinema projectionists.

4) Selective loud sequences of a movie to be loudness controlled in a predictable manner which is previewed by the film maker.

OBJECT OF THE INVENTION ;-

The main object of the present embodiment is to overcome all the associated drawbacks and provide a loudness management system which ensures movies recorded with this system to be played back in cinemas at similar perceived loudness during recording of movie.

Another object of the present invention is to provide for projectionists with a hassle free system for playback of movies in cinemas for maintaining loudness level of the surround sound format.

Another object of the present invention is to provide mixing engineers with a system which can measure loudness of soundtracks and limit loudness according to the needs of the visuals by providing visual categorical inputs to the system. Yet another object of the present invention is to provide customization of playback levels of soundtracks to take care of cultural and environmental differences of different countries ensuring the same perceived loudness across regions.

Further object of the present invention is to provide automatic compensation of target speaker response as per room size.

Other object of the present invention is to provide selective loud sequences of a movie to be loudness controlled in a predictable manner which is previewed by the film maker during content creation.

Still further object of the present invention is to provide quality control and management of cinema equipment installers, mastering engineers, recording studios and cinema projectionists

Another object of the present invention is to provide compensation for loss of perceived loudness by engineers who are exposed to long hours of loud sound.

STATEMENT OF INVENTION:

The present embodiment is a unique and novel system for standardizing loudness levels of soundtracks in cinemas. The present invention carries out quality control of cinema installers, mastering engineers, recording studios and projectionists. The present embodiment provides projectionists with a hassle free system for playback of movies in cinemas for maintaining loudness level of the surround sound format.

SUMMARY OF THE INVENTION:

It is therefore, an aspect of the present invention to provide a system for recording standardized soundtrack level and maintaining playback levels in cinemas to address all the issues faced by various operators in the audio chain. The present invention consists of a mastering system to achieve standardized recording level of soundtracks on disk and a cinema processor with new architecture which addresses various playback issues faced by the operators.

The present invention also takes care of the various regional and cultural differences to standardize a uniform approach worldwide. The present invention also provides usage data to carry out quality control of cinema installers, mastering engineers, recording studios and projectionists.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:-

The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more embodiments of the present invention and, together with the detailed description, serve to explain the principles and implementations of the invention.

In the drawings:

1. Figure 1 is a block diagram showing the A Section of a cinema processor.

2. Figure 2 is a diagram showing graphical representation of the Dynamic Look Up Table.

3. Figure 3 is a diagram showing graphical representation of the Equalization Look Up Table.

4. Figure 4 is a diagram showing graphical representation of the Level Look Up Table.

5. Figure 5 is a diagram showing graphical representation of the Visual category input Look Up Table.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:-

A complete understanding of the present invention may be by reference to the following detailed description which taken in connection with the accompanying drawings, wherein

Figure 1 illustrates a block diagram showing the A Section of a cinema processor. The input selection module selects various input sources connected to the processor. After selection of input, the data is fed to the Control Data Processing module. If the movie has been recorded with this invention, the module will find relevant control data and feed the same to the Dynamic Processing Module, Level Offset Module and The Equalization Offset module. If valid Control Data is not found, the signal is routed via the alternate path consisting of the Multi-band Auto Level Control Module after it is passed through the Format Selection Module for proper channel assignment and level adjustment required for the particular format. The Dynamic Processing module is only active in the presence of valid Control Data from the Control Data Processing Module and the Front Panel DRC switch. If the Front Panel Emergency Switch is activated for a movie, the signal is routed to the Multi-band Auto Level Control Module even if valid Control Data is detected. The Front panel Premier Mode Switch can be activated only in the presence of valid Control Data. When this mode is selected, the Dynamic processing module is bypassed and the studio level of the territory the movie was mixed in is used for playback from the Level LUT. The entire operation of this Loudness management System is contained within the A Section. On completion of these operations, the signal is passed via the Master Fader (which operates between -1 and +1) to the B Section of the processor. The B Section of the processor contains the standard functions available in cinema processors today. These include Delay settings, Equalization and Level Settings for each channel.

Figure 2 illustrates a diagram showing graphical representation of the Dynamic Look Up Table. This LUT stores settings for the multi-band compressor used. The settings are stored in different profiles. Only one profile can be activated at any point in time. Each profiles stores settings in 4 groups as shown in the rows. These groups are used to apply different settings for Left- Right, Centre, LFE (Low frequency effect)and surrounds. This is arranged in groups so that these settings can be adapted for any format such as 5.1, 7.1, object based formats etc. The multi-band compressor has 3 bands for all groups except the LFE which is a single band compressor. For each band, the low frequency and high-frequency cut-off points can be altered, threshold, ratio, Attack and Release times and make-up gain parameters can also be altered to form different profiles. This allows better profiles to be created in the future. When a new better profile is created, the same is updated in the Mastering software. These LUTs are transferred from mastering system to all cinema processors with the use of the dynamic loading process using the control data. When a new profile is created, the new LUT is stored as a new version. The updated version also contains the old profile settings. This helps movies recorded with earlier settings to be played back by the cinema processor the same way as was intended during mixing.

Figure 3 illustrates a diagram showing graphical representation of the Equalization Look Up Table. This table provides equalization offsets for various room volumes. The two columns under room volume named Minimum and Maximum define a range of room volumes in cubic feet for which equalization offsets are defined. This way, different offsets can be defined for different room volumes. Depending on the room volume of the cinema entered by the cinema processor installer in the setup software, the processor derives its corresponding offsets. A level column also allows level offsets to be put in for different room volumes as the perceived loudness changes for a large room to a small room. Different versions of this look up table can be created which allow these offsets to be changed in the future to accommodate new measurement and alignment techniques. If such new techniques are to be applied, the earlier soundtracks play with an offset with the earlier version as per the control data. The control data specifies the version of the LUT the film was recorded with.

Figure 4 illustrates a diagram showing graphical representation of the Level Look Up Table. The Level LUT contains various countries and zones within countries. For each zonal id, three level offsets can be applied. The first offset column is for studios and preview theatres. The second offset column is for commercial cinemas. Within a zone, these two categories can have different offsets. This facility can compensate for the difference in loudness levels between that preferred by film makers due to their long hours of exposure to loud sounds and the loudness levels at which normal consumers watch movies. Each country can also have different offsets to compensate for the cultural differences and the difference in perceived loudness due to environmental differences. The last column of offset controls the output level of the Automatic Level Control module. This compensates for regional loudness differences for movies routed through this module.

Figure 5 illustrates a diagram showing graphical representation of the Visual category input Look Up Table. This LUT is used by the mastering system only. Various sequence categories are created in the mastering system to provide a visual categorical input to the system. This allows the mastering system to recognize the kind of scene the audio relates to. For each such sequence categories, different measurement processes are defined in this LUT. Hence the mastering system uses different measurement modules to measure loudness for various type of sequences. For each of these measurements, maximum permissible loudness parameters are also defined in this LUT. If the actual measured value is beyond the limit mentioned in the LUT, the Dynamic processing module is activated in the control data. This LUT also defines the dynamic profile to be used from the Dynamic LUT depending on how much the measured loudness exceeds the maximum limit set in this LUT.

Figure 6 illustrates a diagram showing graphical representation of the Control Data embedded by the mastering system in the AES Bitstream of the audio master. There are 3 separate control data sent over 3 pairs of AES channels.

Channel 1, 2 Control Data - Line 1 in the diagram shows the information this control data carries and line 2 shows the source from which the mastering system derives this information. The Channel 1,2 Control data contains information about the movie and versions of various Look Up Tables used during the mastering process.

Channel 3, 4 Control Data - Line 1 in the diagram shows the information this control data carries and line 2 shows the source from which the mastering system derives this information. The Channel 3, 4 Control data carries information about the loudness of the film - those measured during the mastering process. It also carries information about which surround sound format the movie was mixed in. The most critical information this control data carries is the dynamic profile to be used. This control data switches on and off the dynamic processing.

Channel 5, 6 Control Data - This is used for dynamic loading for software updates and Look Up Table updates. The updated software is loaded on the mastering system. The same is transferred onto the movie via this control data and this upgrades any cinema processor that this movie is played with.

Detailed description of invention with respect to accompanying drawings :-

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment.

Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter. The present embodiment is a system standardizing recording level of soundtracks and standardizing playback levels in cinemas. The system consists of the followings elements:

a. Mastering and metering system for film mixing studios. b. Tracking system for mastering engineer. c. Cinema processor with new architecture. d. Periodic tracking and approval system for cinema processor equipment installers.

e. Periodic tracking system for cinema playback operations. f. Region-wise tracking and modification of loudness reference levels. g. Film-wise tracking of playback operations across various regions.

Using the above elements, this invention addressees the loudness problem by achieving two important goals

1. Standardizing recording level on disk

2. Standardizing playback level set by operators in cinemas

Managing Loudness within a local territory a. Content origin and Multiband Automatic Level Control

Films, commercials and trailers are mixed in a variety of studios. There are different approaches required in playback of films mixed in studios using this loudness management system and studios not using this system. For studios not using this system, soundtracks can be expected to reach the cinemas at any loudness level and dynamic range. It is impossible for projectionists to keep adjusting the levels for all this content individually. Hence, the approach adopted to playback this content is to use multi-band automatic level control software in the cinema processor. Content mixed in studios with this system will have embedded control data in the AES(Audio Engineering Society Standard) bit stream. The cinema processor designed with this architecture will switch off the multiband auto level control when it senses valid control data. b. Mastering and metering system

Each mixing studio equipped with this system will require this mastering system to be installed. During the mixing processes, the mastering system will remain in metering mode and display the following loudness measurements - dialogue level, LEQ(Energy based equivalent sound level) and peak level. Additional metering options can be upgraded in future using software updates. c. Universal Dialogue Range

The most critical component in loudness control is the dialogue level. Projectionists set playback level in cinemas first based on dialogue level. Subsequently, if there are any very loud portions in the film, they reduce the playback level further. Hence achieving the correct dialogue level on disk is the most crucial component. Given the dynamic range of the cinema system, a particular part of the range should be allocated to dialogues. The SPL range (sound pressure level of human voice) is somewhat constant and the same should be standardised. Currently content arriving in cinemas can have dialogue level ranging from soft whispers to SPL levels comparable to that of airplanes. A permissible dialogue range is fixed and the same can be monitored by the mixing engineer on the mastering system. This permissible dialogue range is referred to as UDR (Universal Dialogue Range). d. Mastering process (step 1)

The mix is first transferred onto the mastering system. After the transfer, the mastering engineer selects various portions of the soundtrack and classifies them into various 'sequence categories', for ex dialogue sequence, action sequence, song sequence etc. These classifications are selected from a drop down menu of pre defined classifications. The dialogue sequences are first measured to check if the average dialogue level confirms to the UDR. This should normally confirm, as the mix engineer can meter this level during the mix. If the dialogue level measured does not confirm to the UDR, the level of the entire soundtrack is pulled down to confirm to the same. e. Loud Sequence Measurement. After the master level is set (if required) and the dialogue level confirms to the UDR, other sequences are measured. Each 'sequence category' in the drop down menu of the LMS mastering system is mapped to a set of measurement processes, for ex, action sequences are measured with LEQ and has an allocated maximum LEQ limit (say action sequence - max LEQ 90). If the measured LEQ level of a particular action sequence is less than LEQ 90, no action is taken. f. Dynamic Range Control

The cinema processor with this facility has multiband compressors for each channel. These multiband compressors operate with fixed settings, or profiles. These profiles can be triggered to be activated by the control data. The processor has a switch called "Dynamic Range Control (DRC)" on the front panel. When this switch is active, the control data during a particular sequence can switch these multiband compressors on to a particular profile. g. Mastering Process (Step 2)

Each sequence of the soundtrack categorized by the mastering engineer, are measured with corresponding measurement processes. If certain sequences exceed the permissible value, predefined profiles for triggering the multiband compressor in the cinema processor are set into the control data of the sequence. The soundtrack itself is not changed in any way. Once these measurements and compressor profile allocation is completed, the soundtrack is rendered to WAV (digital audio file in uncompressed format) files with the control data embedded into the tracks. This completes the mastering process and the soundtrack is ready for DCP (Digital cinema package) creation.

While allocating a compressor profile during mastering, the same is simulated in the monitoring of the studio for checking the results.

2. Fader Level 7

The current recommended playback level for existing cinema processors is 7. However, due to majority of the soundtracks being recorded too loud, the common playback levels are between 5 and 6. New projectionists who have joined in the recent years have always seen their predecessors playing back at 5 and 6 and are not even aware that the recommended playback level is 7. Even if a film is recorded at the correct level, it is played back at 5 or 6.

The cinema processor with this system has a recommended fader level of 0 to overcome the psychological barrier. The fader can be turned to a maximum of +1 or - 1. When the fader is turned from 0, the number starts flashing. This is a clear indication to all projectionists that the recommended fader level is 0.

If the projectionist finds certain sequences too loud, or amplifiers going into clipping during loud portions, he needs to switch on "Dynamic Range Control (DRC)" switch which will activate multiband compressors triggered by control data. This is a far better option than turning the fader down for the entire film. He has the option of turning the fader down to a minimum of -1.

3. Improving cinema calibrations

One of the reasons for a projectionist to turn the fader could be that the theatre is not properly calibrated. Theatres may not be properly calibrated due to two reasons - A) it is calibrated by an untrained engineer who increases surround levels etc as per his wish. B) The engineer does not have proper tools or his calibration tool itself is out of calibration. There is currently no accountability for the cinema engineer.

Cinema processors with this facility can be calibrated only by trained engineers with properly calibrated tools. Such engineers will be provided with a digital license valid for a year. Only when the processor is fed with the valid engineer license on a USB flash drive, will the processor open up the calibration pages. The processor also stores the details of the engineer's license along with date of calibration. Without the presence of the engineer key, the setup software allows only settings files to be saved or uploaded to a new processor.

The engineer license is renewed every year, during which the calibration of his tool is checked and the engineer's work evaluated through usage data from various processors he has calibrated.

Managing Loudness on an international level a. Regional Loudness Reference Levels Different countries, cities and towns have different levels of ambient noise due to traffic congestion etc. Due to this, people in different places perceive loudness differently. For example, a person staying in a busy and noisy city like Mumbai, perceive loudness differently from someone staying in a quiet countryside town.

Due to cultural differences also, people like to hear soundtracks at different levels. For example, movies in South India playback much louder than they playback in Germany.

Since maintaining standard recording level on disk is an integral part of this system, it is necessary to change monitor level calibrations based on countries and zones within countries.

b. Level LUT

Cinema processors using this architecture has a Look Up Table for reference levels of various countries called the "Level LUT". The Level LUT (look up table) contains list of countries and zones with offsets for playback level for each zone. For example, India can be set to +1, while Germany can be set to -1 on the Level LUT. The values in the Level LUT are set by a committee and cannot be changed by installers. When a processor is installed in Germany (set in the installation menu), though it is calibrated at 85dB like all other countries, the processor accesses its relevant offset form the Level LUT and applies it during playback. Hence for Germany (as per the above example), the processor will playback at 85-1 = 84dB.

This affects only films being played back in different countries. Within a zone, all processors have the same playback level.

The level LUT is reviewed from time to time and updated. This feature also allows noise levels of zones to change over a period of time due to infrastructure development.

Result of above Steps

Once the above steps are followed, the results achieved are:

1. Content from unknown studios are played back at standard playback level on processors with the help of the multiband automatic level control. 2. For content created in studios using this invention, dialogue level on disk is standardised

3. For content created in studios using this invention, excessive loud sections can be controlled selectively in a predictable manner using the DRC switch of the processor.

4. Regional differences are adhered to using the Level LUT.

5. Theatre Calibration is controlled using the cinema installer training, evaluation and licensing control.

If all above steps are controlled, it can be assumed that all content in all cinemas can playback at standard level 0.

Hence, if any cinema is not playing a film at 0, it can be assumed that one of the above parameters are incorrect. This variation is tracked on a regular basis and the issues addressed and resolved. This way, the loudness problem can be resolved over a short period of time.

LMS Database (Introduction)

The cinema processors using this invention records the playback level of a movie (fader level -1 to +1), which is mapped to the movie id derived from control data. It also records the playback level for content using the auto level control. Once the fader level (say -1) is set for a particular movie, the processor keeps this in memory and plays back at -1 whenever it detects the same movie id from Control data. If the fader for the movie is set to 0 for a subsequent show, it keeps this setting in memory (last setting).

This recorded playback level along with content id is updated to a LMS (loudness Management System) Master Database over an internet connection (can also be updated manually by an engineer using an encrypted file).

The movie wise playback information for different territories is analyzed from the LMS Master Database to track playback level deviation from 0. Cinemas for which playback deviation is noticed for majority of content, the issue is diagnosed and resolved. Cinema Processor

The cinema processor using this invention has two sections - A section and B section. The B section is similar to existing cinema processors containing speaker equalization, speaker delays and speaker level settings.

The A and B sections are separated by the master volume control. Recommended playback level is 0. The master level control varies from -1 to +1 only. The number on the fader starts flashing as soon as it is turned down beyond -0.5 or turned up above +0.5.

Figure 1 shows the internal ^block diagram of a cinema processor. The A section consists of the following sections: a. Source Selection module - this selects playback between various inputs. b. Control data detection and processing module. c. Format selection module - internal signal routing to playback different formats and the respective level compensations required for format compatibility. d. Multiband automating level control module for level adjustment for content without valid control data. e. Dynamic processing module - This module contains multiband compressors for every channel. The settings of these multiband compressors are stored as profiles in a Dynamic Look Up Table called the "Dynamic LUT".

The compressors can be switched on/off jointly by a switch on the front panel called "Dynamic Range control (DRC)" and control data with "compression on" command. If the front panel switch is in "off mode, only control data with compression command cannot switch on the compressors. The settings of the compressors i.e. compressor prolife is triggered by the control data.

Figure 2 is a representation of the Dynamic LUT. The compressor profile is divided into groups of channels. Group 1 contains settings for Left and Right Channel, Group 2 contains settings for the Centre Channel, Group 3 contains settings for the LFE Channel and Group 4 contains settings for the surround channel. Depending on the format and the number of surround channels, the same Group 4 settings are applied to all surround channels.

The Dynamic LUT can be updated from time to time through software updates. However, the earlier values are retained in the newer version of the LUT, to ensure that films mixed prior to a software update still plays back with the earlier profiles and values.

f. Equalization compensation module - This module provides equalization compensation for all channels. The gain values used by each band of this compensation equalizer module is derived from a Look Up Table called the "Equalization LUT". Figure 3 is a representation of the Equalization LUT. These values are not visible to the system installer or the system user. This module is required for the following reasons:

Currently theatres are calibrated to the X curve. However, the X curve was designed for large theatres. The same X curve needs modifications when applied to small rooms. It is difficult for engineers to judge the amount of compensation to be provided as per the room size. The Equalization LUT provides the compensation required for different sizes. Once the installer inputs the volume of the room in the set-up software, the processor derives the compensation to be put in from the Equalization LUT. The installer can align every room to the X curve and the compensation for smaller rooms is put in by the processor. This makes equalization more simple and predictable.

The X curve itself can change over a period of time as better measurement tools and equipment are made. However, in spite of better alignment procedures being formulated, the same cannot be applied to cinemas as there is too much content already created using the X curve. In the event the X curve is changed in the future, this module will allow compensation to be put in for old films. The new alignment will be carried out with a new version of the Equalization LUT. Earlier films mixed will still play with the earlier version of the Equalization LUT. The control data contains the version numbers of all LUTs used for the films. The processor uses the same version of the LUTs to derive its playback data. g. Loudness Compensation Module - This module provides level compensation for regional and cultural difference across the world. The values of this module are derived from a Look Up Table called the "Level LUT". Figure 4 is a representation of the Level LUT. The values of these are not visible to the system installer or the system user.

The level LUT has 3 columns. The first column contains level offsets of studios in various countries and zones. The second column contains level offsets of cinemas in various countries and zones. The third column contains level offsets for the automatic level control module in various countries and zones.

During installation, a processor is classified to be a studio / screening room processor or a cinema processor from a drop down menu. Depending on this selection, the processor derives it level compensation values from column 1 or 2 of the level LUT. This facility is provided to be able to keep an offset in level between studios and cinemas in a particular territory if this is deemed to be necessary. In some territories, mixing engineers work round the clock and as a result, this affects their perception of loudness. They perceive loudness differently from other people who are not exposed to such long hours of loud sound every day. This facility takes care of such differences and allows screening rooms to playback at the same level as mix rooms, but cinema theatres with an offset. This also helps to achieve consistent recording level on disk across the world.

The playback level for each movie is recorded in every processor. This data is uploaded onto the LMS master database, and then analyzed periodically to monitor how each film is being played back in different territories across the world. Based on this data (LMS data analysis), a committee decides if level offsets are to be provided in different zones across the world. These offsets are applied after due investigation. This is a far reliable method of setting playback levels than leaving it to the discretion of individual projectionists.

Premiere Mode - This is a switch on the front panel of the processor. This mode is selected for premiere and special screenings. When this mode is selected, the processor derives its level offset, not from its regional column, but from the studio column of the region the film was mixed in. The information about the region in which the film was mixed in and the version of the LUT used during the mix is available in the control data. This mode also switches off any dynamic processing (DRC) so that the film is played back with the same settings that were used during mixing. The mode is active only in the presence of valid control data. DRC Switch - This switch activates the multiband compressors in the dynamic processing module along with control data. The control data alone cannot activate the compressors when this switch is off. Once switched on, this switch remains on even after the cinema processor reboots - till it is switched off physically from the front panel.

Emergency Volume Assist Switch - This switch is provided for emergency operation only. This switch is required only if a soundtrack is not mastered properly and lands up in cinemas. Since the main fader cannot go below -1, if a very loud soundtrack lands up in a cinema due to some oversight/ mistake, this switch switches off the control data detection module and hence the automatic level control module gets activated for this film. This condition is stored in processor memory. Every time this film is played back, the Emergency Volume Switch is activated. This information is also updated on the LMS Master Database.

Processor Calibration - The cinema processor opens up the calibration pages of the setup software only when a valid authorization key is fed to it. These keys are provided to engineers who are trained to install this system with proper tools, on a yearly basis. This ensures that the processor is calibrated by trained engineers. Even for processors with auto-calibration functions, it is extremely important to set up the microphones in the correct locations and also to ensure that external devices like digital crossovers etc are properly set up.

The installation software also has the facility to capture the seat numbers on which the microphones were placed during installation. This helps other engineers visiting the same theatre achieve consistent results during calibration.

During installation, the processor needs to be classified as a studio / screening room processor or a cinema processor. The region and zone of the processor needs to be setup along with dimensions of the room for proper functioning of the Equalization LUT and for providing appropriate delays for output channels.

The processor uses pink noise for equalization and switches to band limited pink noise for level calibration. This ensures that the variation in the frequency response does not result in SPL measurement errors.

The processor stores the time, date of alignment along with engineers details from the license key. This information is uploaded onto the LMS Master database. If this processor is found to be incorrectly calibrated from LMS database data analysis statistics, the concerned engineer can be contacted for remedial action.

If the processor is not aligned for over a year, this starts operating in "Uncal" mode.

Control data

Control data for this invention system is generated by the LMS Mastering System. The control data is embedded in the AES bit stream. The control data is divided into the following channel pairs:

Channel 1,2 Control data carries the following information - Movie Type (feature / trailer etc), Movie ID, Country / zone ID of mix studio, Mix Studio ID, Mastering Engineer ID, Level LUT Version, EQ LUT Version, Dynamic LUT Version.

The cinema processor uses the same version of LUTs to playback the soundtrack as per the control data. This might not be the latest version on the LUT. This ensures that the film always plays back the way it was mixed. New changes and improvements in alignment technology, improved dynamic profiles etc does not affect playback of earlier films.

Channel 3, 4 Control data triggers the Dynamic processing module. It also has the option of activating the automatic level control from the mastering software (this feature is not likely to be used). The control data also carries average loudness measurement values for the movie. These readings are stored in the cinema processor and transferred to the LMS master Database to aid in data analysis.

Channel 5,6 control data is used for Dynamic Loading. The entire LUTs used for the film mix is present in this control data. If the cinema processor has an earlier version of the LUTs, the latest version is updated automatically by this Dynamic Loading process. This dynamic loading process is not used for trailers and commercials.

Figure 6 is a representation of the data contained within the control data stream.

LMS Mastering System

The LMS mastering system is installed in mixing studios. This system is made up of 3 major sections: a) System Setup section - This section is used for installing the mastering unit at the studio. Each mastering engineer has a license file. This is a digital file which is fed to the unit via USB. The setup section can only be accessed with the Mastering Engineer license file. This section also contains the details of the studio (studio id) and the country / zone, which is part of all the control data that this unit produces. b) Mastering Section - When a film is signed up to use the LMS system, an authorization file is generated. This file containing all details of the film, like name, language, format etc in an encrypted form is sent to the recording studio. Once this file is provided to the mastering system, a new project for the film is automatically set up.

The project can only be accessed by the mastering engineer, once the mastering engineer license key is fed to this system. The first step in the mastering process is to setup the number of reels, and start and end time codes of each reel (FFOA & LFOA).(First and last frame of action respectively).

The next step is to transfer the mix track from the studio workstation into this mastering system. The mastering system contains a drop down menu, with a list of sequence categories (like dialogue sequence, song sequence, light action sequence, heavy action sequence, Indian song sequence etc .). These sequence definitions are mapped to a list of loudness measurement modules. For example, song sequences are mapped to LEQ measurements. The system also contains a list of maximum allowed measurement for each sequence category, beyond which the "compression on" command is activated in the control data.

Providing Visual References to the System - The mastering engineer defines various sequences in each reel. For example, the start and end time codes of a song is marked. This selection is defined to be a song. Now the system knows that this clip contains a song and uses the appropriate measuring tool. If the measured value exceeds the maximum permissible value for that type of sequence, it activates the compression module of the cinema processor through control data. Depending on how much the measured value has exceeded the maximum permissible value, an , appropriate compression profile is selected from a look up table called the Visual category input LUT - Figure 5. All important sequences in the film are defined in this manner to the system. All portions which are not defined are automatically selected as dialogue sequences.

Once the sequence definition is completed, the measurement process is started. The first measurement that is carried out is the dialogue level measurement in the dialogue sequences. If the measurements confirm to the UDR, the system proceeds towards other measurement. If the measured dialogue level does not confirm to the UDR, the master level of the mix is changed to ensure that the dialogue level confirms to the UDR.

Once the master level is confirmed, all other sequences are measured and dynamic profiles allocated to specific sequences. These profiles are simulated in the audio path for monitoring by embedding control data in the AES signal path and triggering the cinema processor. Once the mix and mastering engineer confirms these profiles, the system is ready to render the final master.

The system generates the final control data files and renders a AES/EBU (Digital input for digital cinema server)audio master with the embedded control data. These files can now be sent for DCP creation.

The latest version of all LUTS are also loaded into the control data for dynamic loading of processors during playback in cinemas. This ensures that any cinema processor with earlier versions of LUTs playing a current movie is immediately upgraded to play back the film with the same version of the LUTs that the film was recorded with. Dynamic loading is not carried out for trailers and commercials due to the restriction in length. c) Monitoring & Metering Section - The monitoring and metering section of the mastering system provides all the measurement tools so that the mixing engineer can measure sequences and provide any compensation in the mix that he desires. This ensures that no major changes are required during mastering, and the mix corresponds exactly to the master created for DCPs. The most important measurement during the mix is the dialogue level measurement to ensure this confirms to the UDR (Union docs residency for documentary art). Hence change of master level can be avoided during the mastering process.

The monitor section of the mastering system allows loudness measurements to be carried out. The start and end time codes are fed in for the measurement, and the type of clip is selected from a drop down list. Once the measurement start is selected, and the workstation played, the mastering system carries out the appropriate measurement between the start and end time codes. On completion, it provides the loudness measurement along with suggested compression profile. The mastering system has a compression simulator section. When "simulate" is selected, the system applies the compression profile between the start and end time codes for subsequent runs. The compressor can be toggled on and off. This allows the mixing engineer to tweak his mix to make it suitable for both on and off modes.

Equalization

X curve for different volumes and EQ LUT

Currently cinemas are calibrated to the X Curve using pink noise as the signal source. However, the X Curve was designed based on large cinemas. Flat speakers in large auditoriums are supposed to follow the X Curve. Any anomalies measured using a Real time Analyzer is equalized.

However, this X Curve is not applicable for smaller rooms. For equalizing these smaller rooms, a curve with a lesser high frequency roll-off should to be followed. This is currently left up to the discretion of installation engineers, and most engineers tend to follow the same X Curve even in smaller rooms. To eliminate this error, the process has been simplified for installation engineers with the help of the Equalization LUT. This LUT has different compensations provided for different room sizes. Once the room volume is fed to the processor during initial setup, it applies the corresponding compensation, and the engineers can continue to calibrate all rooms to the X Curve. The corresponding compensation will be provided by the processor internally. A representation of the Equalization LUT is shown in Figure 3.

Change of X curve

The validity of the X Curve is also currently under debate. There could be better ways of carrying out speaker equalization in the future. However, no improvement are currently possible due to the fact that the X Curve has been followed for over 2 decades and there are far too many films which are already mixed following the X Curve. Any change in the calibration process will create compatibility problems for playing back earlier soundtracks. All studios and theatres cannot be changed overnight. Hence there will always be some studios and theatres following the old alignment and some following the new method. Due to this problem, newer methods of alignment are not possible to implement.

The Equalization LUT also ensures that this problem is eliminated. Any new method of alignment requires earlier soundtracks have to be played back using an equalization compensation. A new version of the Equalization LUT can be released with the equalization compensation for older soundtracks. The control data provides information about the version of the Equalization LUT used during mixing of a particular film, and the processor plays back that film with the corresponding values from the Equalization LUT.

Data Analysis

The cinema processor updates the usage information to the LMS Master database over an internet connection or via an encrypted file uploaded to the LMS Master Database by an engineer. The processor uploads the following information:

1. Movie id (from Control data)

2. Processor Id

3. Region / country

4. Fader level (the last level at which the movie was played)

5. Dynamic Range Control (on/off)

6. Emergency Volume Assist (on/off)

7. Fader level for Automatic Level Control content (last level)

8. Cinema Engineer (person who carried out last calibration)

9. Date of last calibration

10. Type of Movie (Feature / Commercial etc)

11. Mastering Engineer

12. Mixing Studio

13. Region / country where film is mixed 14. Dialogue Level

15. Average LEQ for movie

From the above data available on the LMS Master Database, the following analysis is carried out on a regular basis.

The objective of carrying out the analysis is to understand issues and take remedial action to achieve the following final goal: All movies should play back at fader level 0 in all theatres. If this achieved, it can be concluded that the loudness problem has been resolved. i. Movie Level Analysis - If the movie plays back at 0 in most theatres within the country / region, it can be assumed that the movie has been recorded and mastered correctly.

If the movie plays back at say -1 in all other countries, it means that the level of the original country needs to be raised by 1 in the Level LUT. This is confirmed by similar conditions for other movies.

If the movie plays back at a different level within the same country, say -1, and the same is also observed for other movies, the studio level within the territory should be raised by 1 in the level LUT. ii. Regional Level Analysis - within a region, analysis is carried out to check how films mixed within the same territory are played back. Based on this, modifications are carried out in the Level LUT.

Analysis is also carried out to check how movies mixed in other territories are played back. This analysis provides adequate information to modify the Level LUT. This helps in achieving the following goal - all films are recorded at a standardized level. iii. Cinema Calibration Analysis - Cinemas after installation of this system are tracked for a period of time by the regional office. If the cinema plays majority of the content at 0, it can be assumed that the cinema has been calibrated correctly. If not, remedial action needs to be taken by the regional office.

While carrying out movie analysis, if a few cinemas are found to play a movie at (say -1), while majority of the cinemas in the region are found to play at 0, this would result in starting an investigation. On carrying out Cinema Calibration Analysis of this theatre, if it is found that this cinema is playing majority of the content at -1, it could be assumed that this cinema is not correctly calibrated. The concerned cinema engineer who has calibrated the system is contacted for further investigation. iv. Mastering Analysis - Mastering engineers are evaluated on a regular basis. If all films mastered by an engineer are found to play back at 0 in majority of the cinemas, it can be assumed that the mastering engineer has performed his work satisfactorily. If not, further investigation is carried out to understand the issues faced by him and these issues resolved. Update to the Level LUT could be a possible solution. y v. Cinema Installation Engineer Analysis - The yearly license issued to each cinema engineer, is re-issued after due evaluation. The calibration of his analyzer is checked. An analysis of playback conditions of theatres installed by him is carried out. If most of the theatres installed by him are found to play back movies at 0, his license key is re-issued for another year.

Different formats and Object based formats

This invention is independent of sound formats. The Dynamic LUT comprises of 4 Groups. These settings can be applied to any sound format. The difference between 5.1, 6.1, 7.1 sound formats are merely in the number of surround channels. The same compressor settings of Group 4 are applied to all surround channels depending on the format.

Object based systems compulsorily have 5.1 back-ups. To maintain compatibility, the 5.1 down-mix needs to be of similar loudness levels. Hence the entire mastering operation can be carried out on the 5.1 master. The object based system needs to derive the control data information from the 5.1 soundtrack and apply the same settings within the processor. The Group 4 surround dynamic profile can be applied to all the surround outputs of the object based system.