Coding apparatus for digital image signals

Claim 2

Apparatus according to claim 1 further comprising buffering means (19) for controlling said compression encoding so that a data amount for a two-frame period generated at said encoding means (18) is equal to or less than a target value, wherein said compression encoding for said first frame is controlled by the mean value of threshold values for the preceding two frames, and a buffering process for said second frame is performed so as to limit the generation data amount to a value equal to or less than (L - 1′), where L is said target value for the two-frame period, and 1′ is the generation data amount for said first frame.

Claim 3

Apparatus according to claim 2 wherein said buffering means (19) includes means (37) for detecting a scene change by the generation data amount 1′ for said first frame.

Claim 4

Apparatus according to claim 2 wherein the buffering process is performed so as to limit the generation data amount for one frame period to a value equal to or less than L/2 in the initial status or when said scene change is detected.

Claim 5

Apparatus according to claim 2 wherein said buffering means (19) includes a threshold value table (43) containing first threshold values defined in a level direction and second threshold values for controlling the transmission/non-transmission of the second block and controls the generation data amount by said first and second threshold values.

Claim 6

A coding apparatus for a digital image signal, the apparatus comprising: sub-sampling means (3) to which a digital image signal which has been converted into a signal having a two-dimensional block structure is supplied, and in which a sub-sampling phase is inverted every two sequential frames; means (5) to which an output of said sub-sampling circuit (3) is supplied and which is such that between first and second blocks which are located at spatially the same position and respectively belong to two sequential frames, the first block is always transmitted and a transmission/non-transmission of the second block is adaptively executed; control means (6 to 12) for controlling the transmission/non-transmission in accordance with an absolute value of a difference between values of pixel data at the same position between said first and second blocks; and coding means ( 18 ) to which the pixel data of the first block and the pixel data of the second block which has been decided to be transmitted are supplied and which compression encodes said pixel data on a block unit basis.

Claim 7

Apparatus according to any one of the preceding claims wherein between the pixel data belonging to said first block and the pixel data belonging to said second block, a difference between the two pixel data located at the same position is formed and data of said difference is used as data of said second block.

Claim 8

Apparatus according to any one of the preceding claims wherein said coding means (18) executes a quantization with a bit length shorter than the original bit length so as to be adaptive to a dynamic range which is a difference between maximum and minimum values of each of said blocks.