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对应代码：ffmpeg-pro-09

ffmpe -i 9.mp4 -c copy 9.flv -y （stream copy方式）
ffmpe -i 9.mp4 -vcodec libx264 -acodec aac 9.flv -y
做命令⾏解析的对⽐

命令⾏解析

命令⾏对-c copy的解析

const OptionDef options[] = {
........
    { "c", HAS_ARG | OPT_STRING | OPT_SPEC | OPT_INPUT | OPT_OUTPUT, { .off =
        OFFSET(codec_names) },
        "codec name", "codec" },
    { "codec", HAS_ARG | OPT_STRING | OPT_SPEC | OPT_INPUT | OPT_OUTPUT, { .off =
        OFFSET(codec_names) },
        "codec name", "codec" },
............

对应

typedef struct OptionsContext {
    ........
    SpecifierOpt *codec_names;
    int nb_codec_names;
    .........
}OptionsContext;

static int open_files(OptionGroupList *l,
                      const char *inout,
                      int (*open_file)(OptionsContext*, const char*))
{
    int i, ret;

    for (i = 0; i < l->nb_groups; i++) {
        OptionGroup *g = &l->groups[i];
        OptionsContext o;

        init_options(&o); // 从OptionGroup解析出来的
        o.g = g;

        ret = parse_optgroup(&o, g); // 解析参数 从OptionGroup解析出来的

        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Error parsing options for %s file " "%s.\n", inout, g->arg);
            return ret;
        }

        // 这⾥可以下断点查看o解析出来的codecname
        av_log(NULL, AV_LOG_DEBUG, "Opening an %s file: %s.\n", inout, g->arg);
        ...........
    }

    return 0;
}

创建输出流

choose_encoder

static int choose_encoder(OptionsContext *o, AVFormatContext *s, OutputStream *ost)
{
    enum AVMediaType type = ost->st->codecpar->codec_type;
    char *codec_name = NULL;

    if (type == AVMEDIA_TYPE_VIDEO || type == AVMEDIA_TYPE_AUDIO || type == AVMEDIA_TYPE_SUBTITLE) {
        MATCH_PER_STREAM_OPT(codec_names, str, codec_name, s, ost->st);

        if (!codec_name) {
            ost->st->codecpar->codec_id = av_guess_codec(s->oformat,NULL, s->url, NULL, ost->st->codecpar->codec_type);
            ost->enc = avcodec_find_encoder(ost->st->codecpar->codec_id);// 具体还要看存不存在

            .........

        } else if (!strcmp(codec_name, "copy"))
            ost->stream_copy = 1; // 编码器维持输⼊的即是流拷⻉
        else {
            ost->enc = find_codec_or_die(codec_name, ost->st->codecpar->codec_type, 1);
            ost->st->codecpar->codec_id = ost->enc->id;
        }

        ost->encoding_needed = !ost->stream_copy; // 需要编码
    } else {
        /* no encoding supported for other media types */
        ost->stream_copy = 1; // 不需要重新编码
        ost->encoding_needed = 0;
    }
    return 0;
}

读取packet和写⼊输出流