如何使用libavformat连接2个具有相同编解码器的视频文件（重新复用）？ [英] How to use libavformat to concat 2 video files with same codec (re-muxing)?
问题描述
我已经从FLV格式（视频H264和音频AAC）下载了CDN的视频，并将其重新映射到MP4格式。但视频的长度有限。所以我已经下载了几个部分的视频：从起点开始，在第1点，第2点（通过在url中使用seek参数）。每个点的开始时间早于前一个结束。
使用 av_read_frame 我扫描所有部分，发现相交的数据包不仅具有相同的大小和顺序，他们的dts / pts也由一个恒定值相互转移。所以要连接起始视频，视频在第1点开始，我必须执行以下操作：
1.在输出文件中创建输出标题
2.从启动视频复制所有不相交的数据包。
3.将来自点1的所有不相交的数据包复制到更改的dts值，将其移动到常数
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 in several parts: started at start point, at point 1, at point 2 (by using seek parameter in url). Each point starts little earlier than ending of previous one.
Using av_read_frame i scanned all parts and found that intersecting packets not only have same sizes and order but also their dts/pts shifted from each other by constant value. So to concat starting video with video started at point 1 I must do following:
1. Create output header in output file
2. Copy all non-intersecting packets from starting video.
3. Copy all non-intersecting packets from video started at point 1 with changed dts values by shifted it by constant
如何使用libav（而不是ffmpeg）做所有这些？我读了如何使用libavformat而不使用其他libav库。但是在 libav 中，它不起作用，因为 libav avformat_alloc_output_context2 C>。还有源代码 avconv.c 源码对于像我这样的新手来说太复杂了，以隔离与流复制操作相关的部分。
有人可以提供我的示例： br>
- 打开 input_file1 和 input_file2 （仅当程序与通用教程中的标准不同时才需要）
- 打开和写入头 output_file 具有相同的容器格式和相同的视频和音频格式
- 将数据包从 input_file1 写入 output_file 例如 pos == XXX
- 将数据包从 input_file2 写入 output_file 更改其dts （或任何需要的）通过常数值
- 正确写入预告片
How to do all of this using libav (not ffmpeg)? I read How can libavformat be used without using other libav libraries. But in libav it is not working since there not avformat_alloc_output_context2 in libav. Also source avconv.c source is too complex for newbie like me to isolate parts related to stream copy operations.
Can someone provide me example to:
- open input_file1 and input_file2 (only needed if procedure differs from standard in generic tutorials)
- open and write header for output_file with same container format and same video and audio formats
- write packets from input_file1 to output_file up to packet with for example pos == XXX
- write packets from input_file2 to output_file changing their dts (or whatever needed) by constant value
- write correct trailer
计算时间
推荐答案
确定我发现那段代码，但正如我在评论中所说的一些原因不行让我知道如果你可以修复它
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;
}
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