22.FFmpeg学习笔记 - 封装格式转换(remux)

本篇文章的封装格式转换和上篇文章 21.FFmpeg学习笔记 - 无编码的视频复用器(mux) 其实差不多，只不过是，转换格式输入的是一个文件，从中找到所有的视频流和音频流，然后mux成一个视频文件。过程中也不用调用av_compare_ts来比较时间，因为输入的是一个文件(视频流和音频流已交错排列好)，读到什么，就写什么即可。

#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>




static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag)
{
    AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
    
    printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
           tag,
           av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
           av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
           av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
           pkt->stream_index);
}

static void remux()
{
    const char *in_filename = "/Users/zhw/Desktop/resource/sintel_h264_aac.mkv";
    const char *out_filename = "/Users/zhw/Desktop/sintel.mp4";
    AVOutputFormat *ofmt = NULL;
    AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
    AVPacket pkt;
    int ret, i;
    int stream_index = 0;
    int *stream_mapping = NULL;
    int stream_mapping_size = 0;

    
    if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
        fprintf(stderr, "Could not open input file '%s'", in_filename);
        goto end;
    }
    
    if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
        fprintf(stderr, "Failed to retrieve input stream information");
        goto end;
    }
    
    av_dump_format(ifmt_ctx, 0, in_filename, 0);
    
    avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
    if (!ofmt_ctx) {
        fprintf(stderr, "Could not create output context\n");
        ret = AVERROR_UNKNOWN;
        goto end;
    }
    
    stream_mapping_size = ifmt_ctx->nb_streams;
    stream_mapping = av_mallocz_array(stream_mapping_size, sizeof(*stream_mapping));
    if (!stream_mapping) {
        ret = AVERROR(ENOMEM);
        goto end;
    }
    
    ofmt = ofmt_ctx->oformat;
    
    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        AVStream *out_stream;
        AVStream *in_stream = ifmt_ctx->streams[i];
        AVCodecParameters *in_codecpar = in_stream->codecpar;
        
        if (in_codecpar->codec_type != AVMEDIA_TYPE_AUDIO &&
            in_codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
            in_codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE) {
            stream_mapping[i] = -1;
            continue;
        }
        
        stream_mapping[i] = stream_index++;
        
        out_stream = avformat_new_stream(ofmt_ctx, NULL);
        if (!out_stream) {
            fprintf(stderr, "Failed allocating output stream\n");
            ret = AVERROR_UNKNOWN;
            goto end;
        }
        
        ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);
        if (ret < 0) {
            fprintf(stderr, "Failed to copy codec parameters\n");
            goto end;
        }
        out_stream->codecpar->codec_tag = 0;
    }
    av_dump_format(ofmt_ctx, 0, out_filename, 1);
    
    if (!(ofmt->flags & AVFMT_NOFILE)) {
        ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
        if (ret < 0) {
            fprintf(stderr, "Could not open output file '%s'", out_filename);
            goto end;
        }
    }
    
    ret = avformat_write_header(ofmt_ctx, NULL);
    if (ret < 0) {
        fprintf(stderr, "Error occurred when opening output file\n");
        goto end;
    }
    
    while (1) {
        AVStream *in_stream, *out_stream;
        
        ret = av_read_frame(ifmt_ctx, &pkt);
        if (ret < 0)
            break;
        
        in_stream  = ifmt_ctx->streams[pkt.stream_index];
        if (pkt.stream_index >= stream_mapping_size ||
            stream_mapping[pkt.stream_index] < 0) {
            av_packet_unref(&pkt);
            continue;
        }
        
        log_packet(ifmt_ctx, &pkt, "in");

        pkt.stream_index = stream_mapping[pkt.stream_index];
        out_stream = ofmt_ctx->streams[pkt.stream_index];

        /* copy packet */
        pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
        pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
        pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
        pkt.pos = -1;
        log_packet(ofmt_ctx, &pkt, "out");
        
        ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
        if (ret < 0) {
            fprintf(stderr, "Error muxing packet\n");
            break;
        }
        av_packet_unref(&pkt);
    }
    
    av_write_trailer(ofmt_ctx);
    
end:
    avformat_close_input(&ifmt_ctx);
    
    /* close output */
    if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
        avio_closep(&ofmt_ctx->pb);
    avformat_free_context(ofmt_ctx);
    
    av_freep(&stream_mapping);

    
}