PURPOSE: To prevent an image from being degraded while synchronizing the image and a sound by preparing the plural kinds of parameters corresponding to image processing speed and performing thinning based on these parameters.

CONSTITUTION: The processing of the image/sound compressor is designated by an input from a keyboard 6, and a control part 7 controls the entire device. An image signal stored in a frame memory 2 is separated into a luminance signal and a color difference signal and stored in a frame buffer 3. Concerning the image data stored in the frame buffer 3, the difference from the image data stored in the frame memory 2 is compression encoded by an encoding means 9, and those image data are stored in a memory 5. The information of thinning for each of processing speed is stored in a thinning information memory 11, and the image is recorded while synchronized with the sound by thinning the color difference according to optimum thinning from the thinning information. Since the compression of the image is accelerated by simplifying the image processing by thinning the color difference adaptively to the processing speed, the image and the sound can be synchronously recorded.