ffmpeg只转封装不转码的代码实现

在有些场景下，其实只需要转封装，不需要转码， 大概步骤如下： 1. 打开输入的formatcontext 2. 打开输出文件 3. 打开输出的formatcontext 4. 写文件头 5. 复制codec信息 6. 读取输入frame 7. 写输出frame 8. 写文件尾 9. 关闭输出文件 代码如下：

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1. #include <stdio.h>
2. #include <stdlib.h>
3. #include <libavformat/avformat.h>
4. #include <libavutil/avutil.h>
6. int main(int argc, char *argv[])
7. {
8.     AVPacket pkt;
9.     AVFormatContext *input_fmtctx = NULL;
10.     AVFormatContext *output_fmtctx = NULL;
11.     AVCodecContext *enc_ctx = NULL;
12.     AVCodecContext *dec_ctx = NULL;
13.     AVCodec *encoder = NULL;
14. int ret = 0;
15. int i = 0;
17.     av_register_all();
19. if (avformat_open_input(&input_fmtctx, "./a.avi", NULL, NULL) < 0) {
20.         av_log(NULL, AV_LOG_ERROR, "Cannot open the file %sn", "./a.mp4");
21.         return -ENOENT;
22. }
24. if (avformat_find_stream_info(input_fmtctx,0) < 0) {
25.         av_log(NULL, AV_LOG_ERROR, "bbs.chinaffmpeg.org 孙悟空 Failed to retrieve input stream informationn");
26.         return -EINVAL;
27. }
29.     av_dump_format(input_fmtctx, NULL, "./a.avi", 0);
31. if (avformat_alloc_output_context2(&output_fmtctx, NULL, NULL, "./fuck.mp4") < 0) {
32.         av_log(NULL, AV_LOG_ERROR, "bbs.chinaffmpeg.org 孙悟空 Cannot open the file %sn", "./fuck.mp4");
33.         return -ENOENT;
34. }
36. for (i = 0; i < input_fmtctx->nb_streams; i ) {
37.         AVStream *out_stream = NULL;
38.         AVStream *in_stream = NULL;
39.         in_stream = input_fmtctx->streams;
40.         out_stream = avformat_new_stream(output_fmtctx, NULL);
41. if (out_stream < 0) {
42.             av_log(NULL, AV_LOG_ERROR, "bbs.chinaffmpeg.org 孙悟空 Alloc new Stream errorn");
43.             return -EINVAL;
44. }
46.         avcodec_copy_context(output_fmtctx->streams->codec, input_fmtctx->streams->codec);
47.         out_stream->codec->codec_tag = 0;
48. if (output_fmtctx->oformat->flags & AVFMT_GLOBALHEADER) {
49.             out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
50. }
51. }
52.     av_dump_format(output_fmtctx, NULL, "./fuck.mp4", 1);
53.     av_init_packet(&pkt);
54.     pkt.data = NULL;
55.     pkt.size = 0;
57. if (avio_open(&output_fmtctx->pb, "./fuck.mp4", AVIO_FLAG_WRITE) < 0) {
58.         av_log(NULL, AV_LOG_ERROR, "bbs.chinaffmpeg.org 孙悟空 cannot open the output file '%s'n", "./fuck.mp4");
59.         return -ENOENT;
60. }
62. if ((ret = avformat_write_header(output_fmtctx, NULL)) < 0) {
63.         av_log(NULL, AV_LOG_ERROR, "bbs.chinaffmpeg.org 孙悟空 Cannot write the header for the file '%s' ret = %dn", "fuck.mp4", ret);
64.         return -ENOENT;
65. }
68. while (1) {
69.         AVStream *in_stream = NULL;
70.         AVStream *out_stream = NULL;
72.         ret = av_read_frame(input_fmtctx, &pkt);
73. if (ret < 0) {
74.             av_log(NULL, AV_LOG_ERROR, "bbs.chinaffmpeg.org 孙悟空 read frame error %dn", ret);
75.             break;
76. }
78.         in_stream = input_fmtctx->streams[pkt.stream_index];
79.         out_stream = output_fmtctx->streams[pkt.stream_index];
80.         pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX);
81.         pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX);
82.         pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
83.         pkt.pos = -1;
84.         ret = av_write_frame(output_fmtctx, &pkt);
86. if (ret < 0) {
87.             av_log(NULL, AV_LOG_ERROR, "bbs.chinaffmpeg.org 孙悟空 Muxing Errorn");
88.             break;
89. }
90.         av_free_packet(&pkt);
91. }
93.     av_write_trailer(output_fmtctx);
94.     avformat_close_input(&input_fmtctx);
95.     avio_close(output_fmtctx->pb);
96.     avformat_free_context(output_fmtctx);
98.         return 0;
100. }