How to use libavformat to concat 2 video files with same codec (re-muxing)?

Question

I have downloaded videos from CDN in flv format (video H264 and audio AAC) and remux to them to MP4 format. But videos are limited by length. So i\'ve downloaded each video

Answer 1

I have replaced deprecated methods, and corrections by ALiang are added too. It works.

`/*
 * merge.c
 *
 *  Created on: Nov 17, 2012
 *  Author: arash
 *
 *  Modified on: April 5, 2018
 *  Editor: Chebotarev Michael
 */
/* merge multiple "IDENTICAL" video file into one file */
#include <stdio.h>
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
AVFormatContext *i_fmt_ctx;
AVStream *i_video_stream;
AVFormatContext *o_fmt_ctx;
AVStream *o_video_stream;

int main(int argc, char* argv[])
{
if (argc < 3)
{
    fprintf(stderr, "usage : %s <input> [<input>...] <output>\n", argv[0]);
    return -1;
}

avcodec_register_all();
av_register_all();

/* should set to NULL so that avformat_open_input() allocate a new one */
i_fmt_ctx = NULL;
if (avformat_open_input(&i_fmt_ctx, argv[1], NULL, NULL) != 0)
{
    fprintf(stderr, "could not open input file\n");
    return -1;
}

if (avformat_find_stream_info(i_fmt_ctx, NULL) < 0)
{
    fprintf(stderr, "could not find stream info\n");
    return -1;
}

//av_dump_format(i_fmt_ctx, 0, argv[1], 0);

/* find first video stream */
for (unsigned i = 0; i<i_fmt_ctx->nb_streams; i++)
    if (i_fmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
    {
        i_video_stream = i_fmt_ctx->streams[i];
        break;
    }
if (i_video_stream == NULL)
{
    fprintf(stderr, "didn't find any video stream\n");
    return -1;
}

avformat_alloc_output_context2(&o_fmt_ctx, NULL, NULL, argv[argc - 1]);

/*
* since all input files are supposed to be identical (framerate, dimension, color format, ...)
* we can safely set output codec values from first input file
*/
o_video_stream = avformat_new_stream(o_fmt_ctx, 0);
{
    AVCodecContext *c;
    c = o_video_stream->codec;
    c->bit_rate = 400000;
    c->codec_id = i_video_stream->codec->codec_id;
    c->codec_type = i_video_stream->codec->codec_type;
    c->time_base.num = i_video_stream->time_base.num;
    c->time_base.den = i_video_stream->time_base.den;
    fprintf(stderr, "time_base.num = %d time_base.den = %d\n", c->time_base.num, c->time_base.den);
    c->width = i_video_stream->codec->width;
    c->height = i_video_stream->codec->height;
    c->pix_fmt = i_video_stream->codec->pix_fmt;
    printf("%d %d %d", c->width, c->height, c->pix_fmt);
    c->flags = i_video_stream->codec->flags;
    c->flags |= CODEC_FLAG_GLOBAL_HEADER;
    c->me_range = i_video_stream->codec->me_range;
    c->max_qdiff = i_video_stream->codec->max_qdiff;

    c->qmin = i_video_stream->codec->qmin;
    c->qmax = i_video_stream->codec->qmax;

    c->qcompress = i_video_stream->codec->qcompress;

    c->extradata = i_video_stream->codec->extradata;
    c->extradata_size = i_video_stream->codec->extradata_size;
}

avio_open(&o_fmt_ctx->pb, argv[argc - 1], AVIO_FLAG_WRITE);

/* yes! this is redundant */
avformat_close_input(&i_fmt_ctx);

avformat_write_header(o_fmt_ctx, NULL);

int last_pts = 0;
int last_dts = 0;
for (int i = 1; i<argc - 1; i++)
{
    i_fmt_ctx = NULL;
    if (avformat_open_input(&i_fmt_ctx, argv[i], NULL, NULL) != 0)
    {
        fprintf(stderr, "could not open input file\n");
        return -1;
    }

    if (avformat_find_stream_info(i_fmt_ctx, NULL) < 0)
    {
        fprintf(stderr, "could not find stream info\n");
        return -1;
    }
    av_dump_format(i_fmt_ctx, 0, argv[i], 0);

    /* we only use first video stream of each input file */
    i_video_stream = NULL;
    for (unsigned s = 0; s<i_fmt_ctx->nb_streams; s++)
        if (i_fmt_ctx->streams[s]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            i_video_stream = i_fmt_ctx->streams[s];
            break;
        }

    if (i_video_stream == NULL)
    {
        fprintf(stderr, "didn't find any video stream\n");
        return -1;
    }

    int64_t pts, dts;
    while (1)
    {
        AVPacket i_pkt;
        av_init_packet(&i_pkt);
        i_pkt.size = 0;
        i_pkt.data = NULL;
        if (av_read_frame(i_fmt_ctx, &i_pkt) <0)
            break;
        /*
        * pts and dts should increase monotonically
        * pts should be >= dts
        */
        i_pkt.flags |= AV_PKT_FLAG_KEY;
        pts = i_pkt.pts;
        i_pkt.pts += last_pts;
        dts = i_pkt.dts;
        i_pkt.dts += last_dts;
        i_pkt.stream_index = 0;

        //printf("%lld %lld\n", i_pkt.pts, i_pkt.dts);
        static int num = 1;
        printf("frame %d\n", num++);
        av_interleaved_write_frame(o_fmt_ctx, &i_pkt);
        //av_free_packet(&i_pkt);
        //av_init_packet(&i_pkt);
    }
    last_dts += dts;
    last_pts += pts;

    avformat_close_input(&i_fmt_ctx);
}

av_write_trailer(o_fmt_ctx);

avcodec_close(o_fmt_ctx->streams[0]->codec);
av_freep(&o_fmt_ctx->streams[0]->codec);
av_freep(&o_fmt_ctx->streams[0]);

avio_close(o_fmt_ctx->pb);
av_free(o_fmt_ctx);

return 0;
}`

Answer 2

In av_new_stream()

You should add the following code:

c->extradata = i_video_stream->codec->extradata;
c->extradata_size = i_video_stream->codec->extradata_size;

Answer 3

OK I found that piece of code but as I said in my comment for some reason it doesn't work. let me know if you could fix it

/*
 * merge.c
 *
 *  Created on: Nov 17, 2012
 *      Author: arash
 */

/* merge multiple "IDENTICAL" video file into one file */

#include <stdio.h>

#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"

AVFormatContext *i_fmt_ctx;
AVStream *i_video_stream;

AVFormatContext *o_fmt_ctx;
AVStream *o_video_stream;


int main(int argc, char* argv[])
{
    if (argc < 3)
    {
        fprintf(stderr, "usage : %s <input> [<input>...] <output>\n", argv[0]);
        return -1;
    }

    avcodec_register_all();
    av_register_all();

    /* should set to NULL so that avformat_open_input() allocate a new one */
    i_fmt_ctx = NULL;
    if (avformat_open_input(&i_fmt_ctx, argv[1], NULL, NULL)!=0)
    {
        fprintf(stderr, "could not open input file\n");
        return -1;
    }

    if (av_find_stream_info(i_fmt_ctx)<0)
    {
        fprintf(stderr, "could not find stream info\n");
        return -1;
    }

    //av_dump_format(i_fmt_ctx, 0, argv[1], 0);

    /* find first video stream */
    for (unsigned i=0; i<i_fmt_ctx->nb_streams; i++)
        if (i_fmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            i_video_stream = i_fmt_ctx->streams[i];
            break;
        }
    if (i_video_stream == NULL)
    {
        fprintf(stderr, "didn't find any video stream\n");
        return -1;
    }

    avformat_alloc_output_context2(&o_fmt_ctx, NULL, NULL, argv[argc-1]);

    /*
     * since all input files are supposed to be identical (framerate, dimension, color format, ...)
     * we can safely set output codec values from first input file
     */
    o_video_stream = av_new_stream(o_fmt_ctx, 0);
    {
        AVCodecContext *c;
        c = o_video_stream->codec;
        c->bit_rate = 400000;
        c->codec_id = i_video_stream->codec->codec_id;
        c->codec_type = i_video_stream->codec->codec_type;
        c->time_base.num = i_video_stream->time_base.num;
        c->time_base.den = i_video_stream->time_base.den;
        fprintf(stderr, "time_base.num = %d time_base.den = %d\n", c->time_base.num, c->time_base.den);
        c->width = i_video_stream->codec->width;
        c->height = i_video_stream->codec->height;
        c->pix_fmt = i_video_stream->codec->pix_fmt;
        printf("%d %d %d", c->width, c->height, c->pix_fmt);
        c->flags = i_video_stream->codec->flags;
        c->flags |= CODEC_FLAG_GLOBAL_HEADER;
        c->me_range = i_video_stream->codec->me_range;
        c->max_qdiff = i_video_stream->codec->max_qdiff;

        c->qmin = i_video_stream->codec->qmin;
        c->qmax = i_video_stream->codec->qmax;

        c->qcompress = i_video_stream->codec->qcompress;
    }

    avio_open(&o_fmt_ctx->pb, argv[argc-1], AVIO_FLAG_WRITE);

    /* yes! this is redundant */
    av_close_input_file(i_fmt_ctx);

    avformat_write_header(o_fmt_ctx, NULL);

    int last_pts = 0;
    int last_dts = 0;
    for (int i=1; i<argc-1; i++)
    {
        i_fmt_ctx = NULL;
        if (avformat_open_input(&i_fmt_ctx, argv[i], NULL, NULL)!=0)
        {
            fprintf(stderr, "could not open input file\n");
            return -1;
        }

        if (av_find_stream_info(i_fmt_ctx)<0)
        {
            fprintf(stderr, "could not find stream info\n");
            return -1;
        }
        av_dump_format(i_fmt_ctx, 0, argv[i], 0);

        /* we only use first video stream of each input file */
        i_video_stream = NULL;
        for (unsigned s=0; s<i_fmt_ctx->nb_streams; s++)
            if (i_fmt_ctx->streams[s]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
            {
                i_video_stream = i_fmt_ctx->streams[s];
                break;
            }

        if (i_video_stream == NULL)
        {
            fprintf(stderr, "didn't find any video stream\n");
            return -1;
        }

        int64_t pts, dts;
        while (1)
        {
            AVPacket i_pkt;
            av_init_packet(&i_pkt);
            i_pkt.size = 0;
            i_pkt.data = NULL;
            if (av_read_frame(i_fmt_ctx, &i_pkt) <0 )
                break;
            /*
             * pts and dts should increase monotonically
             * pts should be >= dts
             */
            i_pkt.flags |= AV_PKT_FLAG_KEY;
            pts = i_pkt.pts;
            i_pkt.pts += last_pts;
            dts = i_pkt.dts;
            i_pkt.dts += last_dts;
            i_pkt.stream_index = 0;

            //printf("%lld %lld\n", i_pkt.pts, i_pkt.dts);
            static int num = 1;
            printf("frame %d\n", num++);
            av_interleaved_write_frame(o_fmt_ctx, &i_pkt);
            //av_free_packet(&i_pkt);
            //av_init_packet(&i_pkt);
        }
        last_dts += dts;
        last_pts += pts;

        av_close_input_file(i_fmt_ctx);
    }

    av_write_trailer(o_fmt_ctx);

    avcodec_close(o_fmt_ctx->streams[0]->codec);
    av_freep(&o_fmt_ctx->streams[0]->codec);
    av_freep(&o_fmt_ctx->streams[0]);

    avio_close(o_fmt_ctx->pb);
    av_free(o_fmt_ctx);

    return 0;
}