| 摘要 |
A decoder (1) decodes a first generation MPEG2 bitstream Ao having a long GOP ....IBBPBBPBBPBB... to baseband. A recoder (8) recodes the GOP to a second generation bitstream AI having only intra frames, which are stored in an intra frame store (12). An encoder (4) re-encodes the intra frames of generation 2 as a third generation long GOP. Even if the transcoding parameters of the first generation are reused at the third generation, it is found that occupancy VBV values for the first and third generations tend to differ. This may cause the downstream buffer 2 to under - or over- flow. Thus, at the first generation, the target number of bits for the GOPs is made up of a preset percentage of stuffing bits. If in subsequent generations the number of data bits grows, then correspondingly fewer stuffing bits are used in those generations to maintain a constant GOP size. |
