一個視頻有三個流，視頻流，音頻流，字幕流，我將視頻A的視頻流拿出來，將音樂B的音頻流拿出來，合在一起成新的視頻
還是老規矩直接說c代碼如何運行
註冊組件，打開並獲得MP4文件和MP3文件的信息
av_register_all();
//Input
if ((ret = avformat_open_input(&ifmt_ctx_v, in_filename_v, 0, 0)) < 0) {//打開輸入的視頻文件
LOGE( "Could not open input file.");
goto end;
}
if ((ret = avformat_find_stream_info(ifmt_ctx_v, 0)) < 0) {//獲取視頻文件信息
LOGE( "Failed to retrieve input stream information");
goto end;
}
if ((ret = avformat_open_input(&ifmt_ctx_a, in_filename_a, 0, 0)) < 0) {//打開輸入的音頻文件
LOGE( "Could not open input file.");
goto end;
}
if ((ret = avformat_find_stream_info(ifmt_ctx_a, 0)) < 0) {//獲取音頻文件信息
LOGE( "Failed to retrieve input stream information");
goto end;
}創建輸出文件
//Output
avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);//初始化輸出碼流的AVFormatContext。
if (!ofmt_ctx) {
LOGE( "Could not create output context\n");
ret = AVERROR_UNKNOWN;
return -1;
}
ofmt = ofmt_ctx->oformat;獲取MP4的視頻流和MP3的音頻流
//從輸入的AVStream中獲取一個輸出的out_stream
for (i = 0; i < ifmt_ctx_v->nb_streams; i++) {
//Create output AVStream according to input AVStream
if(ifmt_ctx_v->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
AVStream *in_stream = ifmt_ctx_v->streams[i];
AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);//創建流通道AVStream
videoindex_v=i;
if (!out_stream) {
LOGE( "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
break;
}
videoindex_out=out_stream->index;
//Copy the settings of AVCodecContext
if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 0) {
LOGE( "Failed to copy context from input to output stream codec context\n");
break;
}
out_stream->codec->codec_tag = 0;
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
break;
}
}
for (i = 0; i < ifmt_ctx_a->nb_streams; i++) {
//Create output AVStream according to input AVStream
if(ifmt_ctx_a->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO){
AVStream *in_stream = ifmt_ctx_a->streams[i];
AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
audioindex_a=i;
if (!out_stream) {
LOGE( "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
audioindex_out=out_stream->index;
//Copy the settings of AVCodecContext
if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 0) {
LOGE( "Failed to copy context from input to output stream codec context\n");
goto end;
}
out_stream->codec->codec_tag = 0;
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
break;
}
}獲取輸出文件的信息並打開輸出文件，獲得輸出流
LOGE("==========Output Information==========\n");
av_dump_format(ofmt_ctx, 0, out_filename, 1);
LOGE("======================================\n");
//Open output file
if (!(ofmt->flags & AVFMT_NOFILE)) {
if (avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE) < 0) {//打開輸出文件。
LOGE( "Could not open output file '%s'", out_filename);
return -1;
}
}
//Write file header
if (avformat_write_header(ofmt_ctx, NULL) < 0) {
LOGE( "Error occurred when opening output file\n");
return -1;
}接下來就是邊解碼邊編碼了，這個解碼是解碼視頻流和音頻流，這個兩個流解碼速度需要保持一致
這個通過雙方時間軸來判斷，然後就將解碼的數據編碼放入輸出文件
//Get an AVPacket . av_compare_ts是比較時間戳用的。通過該函數可以決定該寫入視頻還是音頻。
if(av_compare_ts(cur_pts_v,ifmt_ctx_v->streams[videoindex_v]->time_base,cur_pts_a,ifmt_ctx_a->streams[audioindex_a]->time_base) <= 0)開始是先解碼視頻，放入cur_pts_v
if(av_read_frame(ifmt_ctx, &pkt) >= 0){
do{
in_stream = ifmt_ctx->streams[pkt.stream_index];
out_stream = ofmt_ctx->streams[stream_index];
if(pkt.stream_index==videoindex_v){
//FIX：No PTS (Example: Raw H.264) H.264裸流沒有PTS，因此必須手動寫入PTS
//Simple Write PTS
if(pkt.pts==AV_NOPTS_VALUE){
//Write PTS
AVRational time_base1=in_stream->time_base;
//Duration between 2 frames (us)
int64_t calc_duration=(double)AV_TIME_BASE/av_q2d(in_stream->r_frame_rate);
//Parameters
pkt.pts=(double)(frame_index*calc_duration)/(double)(av_q2d(time_base1)*AV_TIME_BASE);
pkt.dts=pkt.pts;
pkt.duration=(double)calc_duration/(double)(av_q2d(time_base1)*AV_TIME_BASE);
frame_index++;
}
cur_pts_v=pkt.pts;
break;
}
}while(av_read_frame(ifmt_ctx, &pkt) >= 0);
}接着是解碼音頻放入cur_pts_a
if(av_read_frame(ifmt_ctx, &pkt) >= 0){
do{
in_stream = ifmt_ctx->streams[pkt.stream_index];
out_stream = ofmt_ctx->streams[stream_index];
if(pkt.stream_index==audioindex_a){
//FIX：No PTS
//Simple Write PTS
if(pkt.pts==AV_NOPTS_VALUE){
//Write PTS
AVRational time_base1=in_stream->time_base;
//Duration between 2 frames (us)
int64_t calc_duration=(double)AV_TIME_BASE/av_q2d(in_stream->r_frame_rate);
//Parameters
pkt.pts=(double)(frame_index*calc_duration)/(double)(av_q2d(time_base1)*AV_TIME_BASE);
pkt.dts=pkt.pts;
pkt.duration=(double)calc_duration/(double)(av_q2d(time_base1)*AV_TIME_BASE);
frame_index++;
}
cur_pts_a=pkt.pts;
break;
}
}while(av_read_frame(ifmt_ctx, &pkt) >= 0);
}else{
break;
}然後就是將之前解碼的數據編碼放入輸出文件，釋放這個pkt
//Convert PTS/DTS
pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, (AVRounding)(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;
pkt.stream_index=stream_index;
LOGE("Write 1 Packet. size:%5d\tpts:%lld\n",pkt.size,pkt.pts);
//Write AVPacket 音頻或視頻裸流
if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0) {
LOGE( "Error muxing packet\n");
break;
}av_free_packet(&pkt);
通過不斷地循環，解碼一下視頻流，解碼一下音頻流，編碼放入輸出文件，這三個步驟不斷循環完成合成視頻
完成輸出視頻，並釋放資源
//Write file trailer
av_write_trailer(ofmt_ctx);#if USE_H264BSF
av_bitstream_filter_close(h264bsfc);
#endif
#if USE_AACBSF
av_bitstream_filter_close(aacbsfc);
#endif
end:
avformat_close_input(&ifmt_ctx_v);
avformat_close_input(&ifmt_ctx_a);
/* close output */
if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
avio_close(ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
if (ret < 0 && ret != AVERROR_EOF) {
LOGE( "Error occurred.\n");
return -1;
}下一次依舊與音頻有關係