ffmpeg by id和by name查找decoder的区别

转自：https://blog.csdn.net/muyuyuzhong/article/details/79735763

同一个 AVCodecID 可能对应多个不同的编解码器 (AVCodec),他们有不同的 AVCodec.name。

avcodec_find_decoder 根据AVCodecID查找，找到先注册的decoder则退出
avcodec_find_decoder_by_name 根据decoder name去查找匹配的decoder，比如同样的AV_CODEC_ID_AAC，但它有“aac_fixed”、“libfdk_aac”等不同的decoder，如果我们要指定aac decoder，则可以使用AVCodec.name去查找。

AVCodec ff_aac_fixed_decoder = {
    .name            = "aac_fixed",
    .long_name       = NULL_IF_CONFIG_SMALL("AAC (Advanced Audio Coding)"),
    .type            = AVMEDIA_TYPE_AUDIO,
    .id              = AV_CODEC_ID_AAC,
    .priv_data_size  = sizeof(AACContext),
    .init            = aac_decode_init,
    .close           = aac_decode_close,
    .decode          = aac_decode_frame,
    .sample_fmts     = (const enum AVSampleFormat[]) {
        AV_SAMPLE_FMT_S32P, AV_SAMPLE_FMT_NONE
    },
    .capabilities    = AV_CODEC_CAP_CHANNEL_CONF | AV_CODEC_CAP_DR1,
    .caps_internal   = FF_CODEC_CAP_INIT_THREADSAFE,
    .channel_layouts = aac_channel_layout,
    .profiles        = NULL_IF_CONFIG_SMALL(ff_aac_profiles),
    .flush = flush,
};

AVCodec ff_libfdk_aac_decoder = {
    .name           = "libfdk_aac",
    .long_name      = NULL_IF_CONFIG_SMALL("Fraunhofer FDK AAC"),
    .type           = AVMEDIA_TYPE_AUDIO,
    .id             = AV_CODEC_ID_AAC,
    .priv_data_size = sizeof(FDKAACDecContext),
    .init           = fdk_aac_decode_init,
    .decode         = fdk_aac_decode_frame,
    .close          = fdk_aac_decode_close,
    .flush          = fdk_aac_decode_flush,
    .capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_CHANNEL_CONF,
    .priv_class     = &fdk_aac_dec_class,
    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE |
                      FF_CODEC_CAP_INIT_CLEANUP,
};