| 摘要 |
A video codec is used to reduce the bandwidth of a video signal for storage and/or transmission. To transmit an uncoded quality colour NTSC television signal in digitized form requires channel bandwidth typically 90-130 Mb/s for the signal in the composite format and 216 Mb/s for the signal in the component format. The proposed video codec achieves a reduction of the required transmission bandwidth by a factor of 2-3 by splitting the input signal into two channels, a main and a complementary channel, and by applying different coding techniques in each. In the main channel the input signal is subsampled and DPCM encoded using a fixed-rate companded quantization, whereas VWL and block coding is used to encode the complementary channel carrying the interpolation error signal. This arrangement seeks to ensure high picture quality while being easily adaptable to different transmission rates and signal formats. In bandwidth-on-demand applications the main channel can be used alone to provide a lesser quality signal, for example CATV quality at 35 Mb/s, with an attendant reduction in system complexity. |
