FFmpeg中MPEG-4编码程序追踪,其他FFMPEG自带编码器同理

FFmpeg中与MPEG-4编码相关的主要文件有mpegvideo.c，h263.c等。

在mpegvideo.c中，
AVCodec mpeg4_encoder = {
   "mpeg4",
   CODEC_TYPE_VIDEO,
   CODEC_ID_MPEG4,
   sizeof(MpegEncContext),
   MPV_encode_init,
   MPV_encode_picture,
   MPV_encode_end,
    .pix_fmts=(enum PixelFormat[]){PIX_FMT_YUV420P, -1},
   .capabilities= CODEC_CAP_DELAY,
};

MPV_encode_picture()
{
encode_picture();
}

encode_picture()
{
//对每个宏块MB进行运动估计
estimate_motion_thread();

encode_thread();
}

encode_thread()
{
encode_mb_hq();
}

encode_mb_hq()
{
encode_mb();
}

encode_mb()
{
encode_mb_internal();
}

encode_mb_internal()
{
//对单一的宏块进行运动补偿
MPV_motion();

//DCT & quantize
dct_quantize_c();

//huffman encode
mpeg4_encode_mb();
}

帧内和帧间的量化矩阵在mpeg4data.h中
const int16_t ff_mpeg4_default_intra_matrix[64] = {
8, 17, 18, 19, 21, 23, 25, 27,
17, 18, 19, 21, 23, 25, 27, 28,
20, 21, 22, 23, 24, 26, 28, 30,
21, 22, 23, 24, 26, 28, 30, 32,
22, 23, 24, 26, 28, 30, 32, 35,
23, 24, 26, 28, 30, 32, 35, 38,
25, 26, 28, 30, 32, 35, 38, 41,
27, 28, 30, 32, 35, 38, 41, 45,
};

const int16_t ff_mpeg4_default_non_intra_matrix[64] = {
16, 17, 18, 19, 20, 21, 22, 23,
17, 18, 19, 20, 21, 22, 23, 24,
18, 19, 20, 21, 22, 23, 24, 25,
19, 20, 21, 22, 23, 24, 26, 27,
20, 21, 22, 23, 25, 26, 27, 28,
21, 22, 23, 24, 26, 27, 28, 30,
22, 23, 24, 26, 27, 28, 30, 31,
23, 24, 25, 27, 28, 30, 31, 33,
};