本文記錄一個基於FFmpeg的視音頻複用器(Simplest FFmpeg muxer)。視音頻複用器(Muxer)即是將視頻壓縮數據(例如H.264)和音頻壓縮數據(例如AAC)合併到一個封裝格式數據(例如MKV)中去。如圖所示。在這個過程中並不涉及到編碼和解碼。
本文記錄的程序將一個H.264編碼的視頻碼流文件和一個MP3編碼的音頻碼流文件,合成爲一個MP4封裝格式的文件。
流程
程序的流程如下圖所示。從流程圖中可以看出,一共初始化了3個AVFormatContext,其中2個用於輸入,1個用於輸出。3個AVFormatContext初始化之後,通過avcodec_copy_context()函數可以將輸入視頻/音頻的參數拷貝至輸出視頻/音頻的AVCodecContext結構體。然後分別調用視頻輸入流和音頻輸入流的av_read_frame(),從視頻輸入流中取出視頻的AVPacket,音頻輸入流中取出音頻的AVPacket,分別將取出的AVPacket寫入到輸出文件中即可。其間用到了一個不太常見的函數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。本文介紹的視音頻複用器,輸入的視頻不一定是H.264裸流文件,音頻也不一定是純音頻文件。可以選擇兩個封裝過的視音頻文件作爲輸入。程序會從視頻輸入文件中“挑”出視頻流,音頻輸入文件中“挑”出音頻流,再將“挑選”出來的視音頻流複用起來。
PS1:對於某些封裝格式(例如MP4/FLV/MKV等)中的H.264,需要用到名稱爲“h264_mp4toannexb”的bitstream filter。
PS2:對於某些封裝格式(例如MP4/FLV/MKV等)中的AAC,需要用到名稱爲“aac_adtstoasc”的bitstream filter。
簡單介紹一下流程中各個重要函數的意義:
avformat_open_input():打開輸入文件。
avcodec_copy_context():賦值AVCodecContext的參數。
avformat_alloc_output_context2():初始化輸出文件。
avio_open():打開輸出文件。
avformat_write_header():寫入文件頭。
av_compare_ts():比較時間戳,決定寫入視頻還是寫入音頻。這個函數相對要少見一些。
av_read_frame():從輸入文件讀取一個AVPacket。
av_interleaved_write_frame():寫入一個AVPacket到輸出文件。
av_write_trailer():寫入文件尾。
代碼
下面貼上代碼:- /**
- * 最簡單的基於FFmpeg的視音頻複用器
- * Simplest FFmpeg Muxer
- *
- * 雷霄驊 Lei Xiaohua
- * [email protected]
- * 中國傳媒大學/數字電視技術
- * Communication University of China / Digital TV Technology
- * http://blog.csdn.net/leixiaohua1020
- *
- * 本程序可以將視頻碼流和音頻碼流打包到一種封裝格式中。
- * 程序中將MP3編碼的音頻碼流和H.264編碼(MPEG2TS封裝中)的視頻碼流打包成
- * MP4封裝格式的文件。
- * 需要注意的是本程序並不改變視音頻的編碼格式。
- *
- * This software mux a video bitstream and a audio bitstream
- * together into a file.
- * In this example, it mux a H.264 bitstream (in MPEG2TS) and
- * a MP3 bitstream file together into MP4 format file.
- *
- */
- #include <stdio.h>
- extern "C"
- {
- #include "libavformat/avformat.h"
- };
- /*
- FIX: H.264 in some container format (FLV, MP4, MKV etc.) need
- "h264_mp4toannexb" bitstream filter (BSF)
- *Add SPS,PPS in front of IDR frame
- *Add start code ("0,0,0,1") in front of NALU
- H.264 in some container (MPEG2TS) don't need this BSF.
- */
- //'1': Use H.264 Bitstream Filter
- #define USE_H264BSF 0
- /*
- FIX:AAC in some container format (FLV, MP4, MKV etc.) need
- "aac_adtstoasc" bitstream filter (BSF)
- */
- //'1': Use AAC Bitstream Filter
- #define USE_AACBSF 0
- int main(int argc, char* argv[])
- {
- AVOutputFormat *ofmt = NULL;
- //輸入對應一個AVFormatContext,輸出對應一個AVFormatContext
- //(Input AVFormatContext and Output AVFormatContext)
- AVFormatContext *ifmt_ctx_v = NULL, *ifmt_ctx_a = NULL,*ofmt_ctx = NULL;
- AVPacket pkt;
- int ret, i;
- char *in_filename_v = "cuc_ieschool.ts";//輸入文件名(Input file URL)
- //char *in_filename_v = "cuc_ieschool.h264";
- //char *in_filename_a = "cuc_ieschool.mp3";
- //char *in_filename_a = "gowest.m4a";
- //char *in_filename_a = "gowest.aac";
- char *in_filename_a = "huoyuanjia.mp3";
- char *out_filename = "cuc_ieschool.mp4";//輸出文件名(Output file URL)
- av_register_all();
- //輸入(Input)
- if ((ret = avformat_open_input(&ifmt_ctx_v, in_filename_v, 0, 0)) < 0) {
- printf( "Could not open input file.");
- goto end;
- }
- if ((ret = avformat_find_stream_info(ifmt_ctx_v, 0)) < 0) {
- printf( "Failed to retrieve input stream information");
- goto end;
- }
- if ((ret = avformat_open_input(&ifmt_ctx_a, in_filename_a, 0, 0)) < 0) {
- printf( "Could not open input file.");
- goto end;
- }
- if ((ret = avformat_find_stream_info(ifmt_ctx_a, 0)) < 0) {
- printf( "Failed to retrieve input stream information");
- goto end;
- }
- printf("Input Information=====================\n");
- av_dump_format(ifmt_ctx_v, 0, in_filename_v, 0);
- av_dump_format(ifmt_ctx_a, 0, in_filename_a, 0);
- printf("======================================\n");
- //輸出(Output)
- avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
- if (!ofmt_ctx) {
- printf( "Could not create output context\n");
- ret = AVERROR_UNKNOWN;
- goto end;
- }
- ofmt = ofmt_ctx->oformat;
- int videoindex_v=-1,videoindex_out=-1;
- for (i = 0; i < ifmt_ctx_v->nb_streams; i++) {
- //根據輸入流創建輸出流(Create output AVStream according to input AVStream)
- if(ifmt_ctx_v->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
- videoindex_v=i;
- AVStream *in_stream = ifmt_ctx_v->streams[i];
- AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
- if (!out_stream) {
- printf( "Failed allocating output stream\n");
- ret = AVERROR_UNKNOWN;
- goto end;
- }
- videoindex_out=out_stream->index;
- //複製AVCodecContext的設置(Copy the settings of AVCodecContext)
- if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 0) {
- printf( "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;
- }
- }
- int audioindex_a=-1,audioindex_out=-1;
- for (i = 0; i < ifmt_ctx_a->nb_streams; i++) {
- //根據輸入流創建輸出流(Create output AVStream according to input AVStream)
- if(ifmt_ctx_a->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO){
- audioindex_a=i;
- AVStream *in_stream = ifmt_ctx_a->streams[i];
- AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
- if (!out_stream) {
- printf( "Failed allocating output stream\n");
- ret = AVERROR_UNKNOWN;
- goto end;
- }
- audioindex_out=out_stream->index;
- //複製AVCodecContext的設置(Copy the settings of AVCodecContext)
- if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 0) {
- printf( "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;
- }
- }
- //輸出一下格式------------------
- printf("Output Information====================\n");
- av_dump_format(ofmt_ctx, 0, out_filename, 1);
- printf("======================================\n");
- //打開輸出文件(Open output file)
- if (!(ofmt->flags & AVFMT_NOFILE)) {
- if (avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE) < 0) {
- printf( "Could not open output file '%s'", out_filename);
- goto end;
- }
- }
- //寫文件頭(Write file header)
- if (avformat_write_header(ofmt_ctx, NULL) < 0) {
- printf( "Error occurred when opening output file\n");
- goto end;
- }
- int frame_index=0;
- int64_t cur_pts_v=0,cur_pts_a=0;
- //FIX
- #if USE_H264BSF
- AVBitStreamFilterContext* h264bsfc = av_bitstream_filter_init("h264_mp4toannexb");
- #endif
- #if USE_AACBSF
- AVBitStreamFilterContext* aacbsfc = av_bitstream_filter_init("aac_adtstoasc");
- #endif
- while (1) {
- AVFormatContext *ifmt_ctx;
- int stream_index=0;
- AVStream *in_stream, *out_stream;
- //獲取一個AVPacket(Get an AVPacket)
- 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){
- ifmt_ctx=ifmt_ctx_v;
- stream_index=videoindex_out;
- if(av_read_frame(ifmt_ctx, &pkt) >= 0){
- do{
- if(pkt.stream_index==videoindex_v){
- cur_pts_v=pkt.pts;
- break;
- }
- }while(av_read_frame(ifmt_ctx, &pkt) >= 0);
- }else{
- break;
- }
- }else{
- ifmt_ctx=ifmt_ctx_a;
- stream_index=audioindex_out;
- if(av_read_frame(ifmt_ctx, &pkt) >= 0){
- do{
- if(pkt.stream_index==audioindex_a){
- cur_pts_a=pkt.pts;
- break;
- }
- }while(av_read_frame(ifmt_ctx, &pkt) >= 0);
- }else{
- break;
- }
- }
- in_stream = ifmt_ctx->streams[pkt.stream_index];
- out_stream = ofmt_ctx->streams[stream_index];
- //FIX
- #if USE_H264BSF
- av_bitstream_filter_filter(h264bsfc, in_stream->codec, NULL, &pkt.data, &pkt.size, pkt.data, pkt.size, 0);
- #endif
- #if USE_AACBSF
- av_bitstream_filter_filter(aacbsfc, in_stream->codec, NULL, &pkt.data, &pkt.size, pkt.data, pkt.size, 0);
- #endif
- //FIX:No PTS (Example: Raw H.264)
- //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++;
- }
- /* copy packet */
- //轉換PTS/DTS(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;
- printf("Write 1 Packet. size:%5d\tpts:%8d\n",pkt.size,pkt.pts);
- //寫入(Write)
- if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0) {
- printf( "Error muxing packet\n");
- break;
- }
- av_free_packet(&pkt);
- }
- //寫文件尾(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) {
- printf( "Error occurred.\n");
- return -1;
- }
- return 0;
- }
結果
輸入文件爲:視頻:cuc_ieschool.ts
音頻:huoyuanjia.mp3
cuc_ieschool.mp4
輸出的文件視頻爲“cuc_ieschool”,配合“霍元甲”的音頻。
下載
SourceForge項目主頁:
https://sourceforge.net/projects/simplestffmpegformat/
CSDN下載