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2023-03-24：音视频mp3和h264混合（muxer）编码为mp4，用go语言编写。

答案2023-03-24：

这是一个使用FFmpeg库将MP3和H.264混合编码为MP4的Go语言程序。程序的大体过程如下：

1.设置FFmpeg库路径和环境变量。

2.检查并创建输出目录，以及输入视频和音频文件。

3.打开输入视频文件并查找视频流，打开输入音频文件并查找音频流。

4.新建输出上下文，并为视频和音频创建新的输出流。

5.打开输出文件。

6.写输出文件头。

7.读取输入视频和音频帧，将它们转换为输出格式，写入输出文件。在这个过程中，需要进行PTS/DTS转换和比特流过滤（如果需要）。

8.写输出文件尾。

9.清理资源并关闭输入和输出文件。

10.播放输出文件（可选）。

代码见github/moonfdd/ffmpeg-go库。

执行命令：

go run ./examples/a24.video_muxer_mp3h2642mp4/main.go

代码参考24：音视频mp3和h264混合（muxer）编码为mp4，代码如下：

// https://feater.top/ffmpeg/ffmpeg-muxer-encode-mp3-h264-to-mp4
package mainimport ("fmt""os""os/exec""unsafe""github.com/moonfdd/ffmpeg-go/ffcommon""github.com/moonfdd/ffmpeg-go/libavcodec""github.com/moonfdd/ffmpeg-go/libavformat""github.com/moonfdd/ffmpeg-go/libavutil"
)/*
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
const USE_H264BSF = 0/*
FIX:AAC in some container format (FLV, MP4, MKV etc.) need
"aac_adtstoasc" bitstream filter (BSF)
*/
//'1': Use AAC Bitstream Filter
const USE_AACBSF = 0func main() {os.Setenv("Path", os.Getenv("Path")+";./lib")ffcommon.SetAvutilPath("./lib/avutil-56.dll")ffcommon.SetAvcodecPath("./lib/avcodec-58.dll")ffcommon.SetAvdevicePath("./lib/avdevice-58.dll")ffcommon.SetAvfilterPath("./lib/avfilter-56.dll")ffcommon.SetAvformatPath("./lib/avformat-58.dll")ffcommon.SetAvpostprocPath("./lib/postproc-55.dll")ffcommon.SetAvswresamplePath("./lib/swresample-3.dll")ffcommon.SetAvswscalePath("./lib/swscale-5.dll")genDir := "./out"_, err := os.Stat(genDir)if err != nil {if os.IsNotExist(err) {os.Mkdir(genDir, 0777) //  Everyone can read write and execute}}inFilenameVideo := "./out/a24.h264"inFilenameAudio := "./out/a24.aac"outFilename := "./out/a24.mp4"_, err = os.Stat(inFilenameVideo)if err != nil {if os.IsNotExist(err) {fmt.Println("create h264 file")exec.Command("./lib/ffmpeg", "-i", "./resources/big_buck_bunny.mp4", "-vcodec", "copy", "-an", inFilenameVideo).Output()}}_, err = os.Stat(inFilenameAudio)if err != nil {if os.IsNotExist(err) {fmt.Println("create aac file")exec.Command("./lib/ffmpeg", "-i", "./resources/big_buck_bunny.mp4", "-acodec", "copy", "-vn", inFilenameAudio).Output()}}var ifmtCtxVideo, ifmtCtxAudio, ofmtCtx *libavformat.AVFormatContextvar packet libavcodec.AVPacketvar inVideoIndex, inAudioIndex ffcommon.FInt = -1, -1var outVideoIndex, outAudioIndex ffcommon.FInt = -1, -1var frameIndex ffcommon.FInt = 0var curPstVideo, curPstAudio ffcommon.FInt64T = 0, 0var ret ffcommon.FInt = 0var i ffcommon.FUnsignedInt = 0var h264bsfc, aacbsfc *libavcodec.AVBitStreamFilterContext//打开输入视频文件ret = libavformat.AvformatOpenInput(&ifmtCtxVideo, inFilenameVideo, nil, nil)if ret < 0 {fmt.Printf("can't open input video file\n")goto end}//查找输入流ret = ifmtCtxVideo.AvformatFindStreamInfo(nil)if ret < 0 {fmt.Printf("failed to retrieve input video stream information\n")goto end}//打开输入音频文件ret = libavformat.AvformatOpenInput(&ifmtCtxAudio, inFilenameAudio, nil, nil)if ret < 0 {fmt.Printf("can't open input audio file\n")goto end}//查找输入流ret = ifmtCtxAudio.AvformatFindStreamInfo(nil)if ret < 0 {fmt.Printf("failed to retrieve input audio stream information\n")goto end}fmt.Printf("===========Input Information==========\n")ifmtCtxVideo.AvDumpFormat(0, inFilenameVideo, 0)ifmtCtxAudio.AvDumpFormat(0, inFilenameAudio, 0)fmt.Printf("======================================\n")//新建输出上下文libavformat.AvformatAllocOutputContext2(&ofmtCtx, nil, "", outFilename)if ofmtCtx == nil {fmt.Printf("can't create output context\n")goto end}//视频输入流for i = 0; i < ifmtCtxVideo.NbStreams; i++ {if ifmtCtxVideo.GetStream(i).Codecpar.CodecType == libavutil.AVMEDIA_TYPE_VIDEO {inStream := ifmtCtxVideo.GetStream(i)outStream := ofmtCtx.AvformatNewStream(nil)inVideoIndex = int32(i)if outStream == nil {fmt.Printf("failed to allocate output stream\n")goto end}outVideoIndex = outStream.Indexif libavcodec.AvcodecParametersCopy(outStream.Codecpar, inStream.Codecpar) < 0 {fmt.Printf("faild to copy context from input to output stream")goto end}outStream.Codecpar.CodecTag = 0break}}//音频输入流for i = 0; i < ifmtCtxAudio.NbStreams; i++ {if ifmtCtxAudio.GetStream(i).Codecpar.CodecType == libavutil.AVMEDIA_TYPE_AUDIO {inStream := ifmtCtxAudio.GetStream(i)outStream := ofmtCtx.AvformatNewStream(nil)inAudioIndex = int32(i)if outStream == nil {fmt.Printf("failed to allocate output stream\n")goto end}outAudioIndex = outStream.Indexif libavcodec.AvcodecParametersCopy(outStream.Codecpar, inStream.Codecpar) < 0 {fmt.Printf("faild to copy context from input to output stream")goto end}outStream.Codecpar.CodecTag = 0break}}fmt.Printf("==========Output Information==========\n")ofmtCtx.AvDumpFormat(0, outFilename, 1)fmt.Printf("======================================\n")//打开输入文件if ofmtCtx.Oformat.Flags&libavformat.AVFMT_NOFILE == 0 {if libavformat.AvioOpen(&ofmtCtx.Pb, outFilename, libavformat.AVIO_FLAG_WRITE) < 0 {fmt.Printf("can't open out file\n")goto end}}//写文件头if ofmtCtx.AvformatWriteHeader(nil) < 0 {fmt.Printf("Error occurred when opening output file\n")goto end}if USE_H264BSF != 0 {h264bsfc = libavcodec.AvBitstreamFilterInit("h264_mp4toannexb")}if USE_AACBSF != 0 {aacbsfc = libavcodec.AvBitstreamFilterInit("aac_adtstoasc")}for {var ifmtCtx *libavformat.AVFormatContextvar inStream, outStream *libavformat.AVStreamvar streamIndex ffcommon.FInt = 0if libavutil.AvCompareTs(curPstVideo, ifmtCtxVideo.GetStream(uint32(inVideoIndex)).TimeBase, curPstAudio, ifmtCtxAudio.GetStream(uint32(inAudioIndex)).TimeBase) < 0 {ifmtCtx = ifmtCtxVideostreamIndex = outVideoIndexif ifmtCtx.AvReadFrame(&packet) >= 0 {for {inStream = ifmtCtx.GetStream(packet.StreamIndex)outStream = ofmtCtx.GetStream(uint32(streamIndex))if packet.StreamIndex == uint32(inVideoIndex) {//Fix: No PTS(Example: Raw H.264//Simple Write PTSif packet.Pts == libavutil.AV_NOPTS_VALUE {//write PTStimeBase1 := inStream.TimeBase//Duration between 2 framescalcDuration := int64(libavutil.AV_TIME_BASE / libavutil.AvQ2d(inStream.RFrameRate))//Parameterspacket.Pts = int64((float64(frameIndex) * float64(calcDuration)) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))packet.Dts = packet.Ptspacket.Duration = int64(float64(calcDuration) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))frameIndex++}curPstVideo = packet.Ptsbreak}if ifmtCtx.AvReadFrame(&packet) >= 0 {} else {break}}} else {break}} else {ifmtCtx = ifmtCtxAudiostreamIndex = outAudioIndexif ifmtCtx.AvReadFrame(&packet) >= 0 {for {inStream = ifmtCtx.GetStream(packet.StreamIndex)outStream = ofmtCtx.GetStream(uint32(streamIndex))if packet.StreamIndex == uint32(inAudioIndex) {//Fix: No PTS(Example: Raw H.264//Simple Write PTSif packet.Pts == libavutil.AV_NOPTS_VALUE {//write PTStimeBase1 := inStream.TimeBase//Duration between 2 framescalcDuration := int64(libavutil.AV_TIME_BASE / libavutil.AvQ2d(inStream.RFrameRate))//Parameterspacket.Pts = int64((float64(frameIndex) * float64(calcDuration)) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))packet.Dts = packet.Ptspacket.Duration = int64(float64(calcDuration) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))frameIndex++}curPstAudio = packet.Ptsbreak}if ifmtCtx.AvReadFrame(&packet) >= 0 {} else {break}}} else {break}}//FIX:Bitstream Filterif USE_H264BSF != 0 {h264bsfc.AvBitstreamFilterFilter(inStream.Codec, "", &packet.Data, (*int32)(unsafe.Pointer(&packet.Size)), packet.Data, int32(packet.Size), 0)}if USE_AACBSF != 0 {aacbsfc.AvBitstreamFilterFilter(outStream.Codec, "", &packet.Data, (*int32)(unsafe.Pointer(&packet.Size)), packet.Data, int32(packet.Size), 0)}//Convert PTS/DTSpacket.Pts = libavutil.AvRescaleQRnd(packet.Pts, inStream.TimeBase, outStream.TimeBase, libavutil.AV_ROUND_NEAR_INF|libavutil.AV_ROUND_PASS_MINMAX)packet.Dts = libavutil.AvRescaleQRnd(packet.Dts, inStream.TimeBase, outStream.TimeBase, libavutil.AV_ROUND_NEAR_INF|libavutil.AV_ROUND_PASS_MINMAX)packet.Duration = libavutil.AvRescaleQ(packet.Duration, inStream.TimeBase, outStream.TimeBase)packet.Pos = -1packet.StreamIndex = uint32(streamIndex)//writeif ofmtCtx.AvInterleavedWriteFrame(&packet) < 0 {fmt.Printf("error muxing packet")break}packet.AvPacketUnref()}//Write file trailerofmtCtx.AvWriteTrailer()if USE_H264BSF != 0 {h264bsfc.AvBitstreamFilterClose()}if USE_AACBSF != 0 {aacbsfc.AvBitstreamFilterClose()}end:libavformat.AvformatCloseInput(&ifmtCtxVideo)libavformat.AvformatCloseInput(&ifmtCtxAudio)if ofmtCtx != nil && ofmtCtx.Oformat.Flags&libavformat.AVFMT_NOFILE == 0 {ofmtCtx.Pb.AvioClose()}ofmtCtx.AvformatFreeContext()fmt.Println("-----------------------------------------")_, err = exec.Command("./lib/ffplay.exe", outFilename).Output()if err != nil {fmt.Println("play err = ", err)}
}