DEVICE FOR MEASURING TELEVISION SIGNALS

DESCRIPTION

The present invention relates to a device for measuring television signals. More in particular, the present invention relates to a device for measuring television signals which is especially suitable for use by an installer for decrypting the signal when setting up digital receivers. As known, digital television signal receivers are based on the conversion of the analog video signal into a digital video signal; this function is provided by using known video/audio signal compression techniques, according to which any redundant information is deleted. The information transmitted through video and audio signals is often subject to interference and noise that must be removed because they affect the quality of the signal received by the end user. Traditional instruments measure digital signals in terms of digital signal strength (which relates to the energy contribution of the digital signal), carrier/noise ratio and error rate; the latter value is especially important, in that it is strictly related to the quality of television images. When the number of errors is small, the correction instruments can reconstruct the lost data and provide a comfortable view of the television images. On the contrary, a high error rate subjects the correction system to an excessive workload, so that signal reconstruction may be affected by image portions with a mosaic effect, i.e. low-quality images different from those transmitted by the broadcaster. Measuring digital signals for high-quality video broadcasting has gained much importance in recent years, when, among other things, digital television has become rapidly widespread. Moreover, with the spread of digital pay television, including both digital terrestrial and satellite broadcasting, for some types of broadcast data complex encryption algorithms have been used for the purpose of protecting the data as it is being broadcast; such encrypted or protected data, once it has arrived at the end user's apparatus, is decrypted and can thus be enjoyed by the user. In order to decrypt the signal and enjoy the broadcast data, the installer- user must use a card, commonly called "smartcard", which contains a code for identifying and enabling or decrypting the signal received. Smartcards are supplied by the various digital television broadcasters, who may set beforehand, by using suitable electronic keys,

the access to certain levels of programs and/or data.

When carrying out measurements for the purpose of setting up the system for receiving high-quality images and sound, the installer-user needs to have access to the signals transmitted in encrypted mode; therefore, in addition to the proper smartcard for the encrypted transmission, the installer-user must also have an appropriate CAM module (Conditional Access Module) suitable for the smartcard type in use and adapted to decode encrypted signals; with the smartcard inserted in the CAM module, the installer-user can display the images correctly and carry out all the necessary measurements and verifications. Along with the appropriate smartcard for the specific type of encrypted transmission, the installer-user must also be equipped with the corresponding conditional access module, or CAM, to be inserted into the interface called "common interface" (CI), i.e. the slot for the CAM and the smartcard employed by the provider of the signal or data for which a measurement and/or verification is to be carried out. Every provider uses a different conditional access system, such as, for example, those used for the Mediaguard, Irdeto, Conax, Crypto works, Viaccess, etc. systems.

It is the object of the present invention to overcome the above-mentioned drawback. More in particular, it is the object of the present invention to provide a device for measuring video and audio television signals which allows the installer-user to read multiple smartcards without having to buy or bring along all the modules, whether CAMs or other modules, which are required for the different providers to be installed.

It is another object of the present invention to provide a device which allows to enhance the level of security or protection against digital television signal "piracy". It is a further object of the present invention to provide the users with a device for measuring television signals which is adapted to ensure a high level of robustness and reliability over time and which can be manufactured easily and economically.

These and other objects are achieved through the device for analysing television signals according to the present invention, which comprises a processor or CPU (Central Processing Unit), at least one block or "RF tuner" (Radio Frequency Tuner) adapted to lock the frequency of the signal to be analysed, at least one block defined by a digital demodulator, and a "TS mux" (Transport Stream Multiplexer) block which forms the digital stream to be sent to the system that prepares the data for transmission, said device also comprising a macroblock which incorporates means for reading and/or encoding a plurality of different smartcards belonging to different digital television broadcasters.

The construction and functional characteristics of the device for analysing television signals according to the present invention will become apparent from the following detailed description, in which reference will be made to the annexed drawing representing a preferred but non-limiting embodiment thereof, wherein: Fig. 1 is a block diagram that shows the operation of the device for analysing television signals according to the present invention.

Referring to the above-mentioned drawing, the device for analysing television signals according to the present invention, designated as a whole by reference numeral 10, comprises a processor 12 consisting of a "CPU" (Central Processing Unit) adapted to control all the internal functions and activities of the device.

Said processor 12 controls and handles at least one block 14, or "RF tuner" (Radio Frequency Tuner), whose function is to lock the frequency of the signal to be analysed. The frequency of the signal locked through block 14 is sent to at least one block 16 defined by a "digital demodulator", whose function is to demodulate the input digital signal and send the demodulated signal to a subsequent block 18, or "TS mux" (Transport Stream Multiplexer), which forms the digital stream to be sent to the system that prepares the data for transmission, i.e. macroblock 19, indicated by the dashed line in Fig. 1. The signal or protocol containing the audio and video communication data, commonly called "transport stream", outputted by block 18 contains a plurality of digital services, e.g. video and/or audio services, interactive services, data services, etc; if a service is of the type encrypted through a conditional access module (CAM), it will be necessary to use a smartcard (schematised by block 20) in order to gain access to the service and display the video signal through a display 22, and/or play the audio signal through a sound system 24. Block 20 or smartcard allows the installer-user to acquire the television signal's encryption keys or codes, decrypt the television signal, and return a decrypted signal, which will then be handled as described below.

Smartcard 20, through a block 26 or "smartcard reader" that defines an electric interface, is connected to a block 28 or "key decryptor". Said block 28 is interfaced with smartcard 20, which is read by means of block 26, by using a proprietary protocol (which is different for the various smartcards) dedicated to the specific smartcard in use, as well as with an additional processor 30, called "decoding/decrypting CPU", for the purpose of requesting the encrypted keys for reading that specific smartcard.

Block 28 or "key decryptor" sends said encrypted keys to the smartcard or block 20 through block 26, and then receives from block 20 the decrypted keys, which are subsequently sent to the additional processor or block 30.

The active transport stream, selected by block 18 or "TS mux", is sent to a block 32 or "Demux", which filters the video and/or audio and/or other digital data packets, thus allowing the various original broadcast channels to be separated. Said block 32 also receives from block 30 instructions for collecting and filtering the encrypted keys of the data stream sent to block 28, or "key decryptor", which is interfaced with smartcard 20 in the above- described manner. Block 28 sends the encrypted keys to smartcard 20 and receives from the latter the "cleaned", i.e. decrypted, keys. Said decrypted keys are then processed by the additional CPU 30 and sent to a decoding block 34, or "descrambler", which decrypts the encrypted data packet or transport stream by using the decrypted keys outputted by block 28. The transport stream data packet thus decrypted, which is now in a displayable format, is then sent to a block 36, or "Audio/Video Decoder", which decodes the audio and video signals of the digital transmission and sends them to sound system 24 and to display 22, respectively.

The above-mentioned block 28 or "key decryptor" is a part of macroblock 19, which incorporates all those components which are necessary for the operation of multiple CI modules; thus, advantageously, the installer-user will not have to buy and bring along all the CI modules required by the different providers of encrypted digital transmissions. As a matter of fact, the "key decryptor" block incorporates into a single block the following: the entire control logic for different smartcards, protocols for the various types of "proprietary" smartcards (for different conditional access systems, among which Mediaguard, Irdeto, Viaccess, etc.), and the whole communication to and from CPU 30 for exchanging the packets involved in decoding a digital service (ECM/EMM packets, PMT tables, etc.). A further advantage is that the device according to the invention allows to enhance the level of security or protection against digital television signal "piracy". The single "external" interface is in fact the only port used for communicating with the smartcard, and such communication is intrinsically protected by the proprietary communication protocol. The digital transport stream, which in Common Interface systems contains the decrypted output digital service, is by no means accessible from outside the apparatus, thus preventing any type of hardware hacking on the stream (e.g. digital recording of the decoded service onto

an external storage medium).

A further advantage is provided by the fact that the device according to the invention can be manufactured at low costs.

Unlike a "minimal" digital solution consisting only of block 19 without blocks 26 and 28, the presence of said blocks 26 and 28 makes the device for receiving and displaying digital signals complete and universal. Furthermore, the absence of a Common Interface slot allows to reduce the overall dimensions of the device.

The invention has been described herein with reference to an explanatory, non-limiting embodiment; in the light of the above description, it will be apparent to those skilled in the art that it may be subject to many changes or variations. Therefore, the present invention is meant to embrace any changes or variations falling within the spirit and scope of the appended claims.