2023-03-24：音視訊mp3和h264混合（muxer）編碼為mp4，用go語言編寫。
答案2023-03-24：
這是一個使用FFmpeg庫将MP3和H.264混合編碼為MP4的Go語言程式。程式的大體過程如下：
1.設定FFmpeg庫路徑和環境變量。
2.檢查并建立輸出目錄，以及輸入視訊和音頻檔案。
3.打開輸入視訊檔案并查找視訊流，打開輸入音頻檔案并查找音頻流。
4.建立輸出上下文，并為視訊和音頻建立新的輸出流。
5.打開輸出檔案。
6.寫輸出檔案頭。
7.讀取輸入視訊和音頻幀，将它們轉換為輸出格式，寫入輸出檔案。在這個過程中，需要進行PTS/DTS轉換和比特流過濾（如果需要）。
8.寫輸出檔案尾。
9.清理資源并關閉輸入和輸出檔案。
10.播放輸出檔案（可選）。
代碼見github/moonfdd/ffmpeg-go庫。
執行指令：
go run ./examples/a24.video_muxer_mp3h2642mp4/main.go 代碼參考[24：音視訊mp3和h264混合（muxer）編碼為mp4](https://feater.top/ffmpeg/ffmpeg-muxer-encode-mp3-h264-to-mp4)，代碼如下：
// https://feater.top/ffmpeg/ffmpeg-muxer-encode-mp3-h264-to-mp4
package main
import (
"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 = 0
func 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.AVFormatContext
var packet libavcodec.AVPacket
var inVideoIndex, inAudioIndex ffcommon.FInt = -1, -1
var outVideoIndex, outAudioIndex ffcommon.FInt = -1, -1
var frameIndex ffcommon.FInt = 0
var curPstVideo, curPstAudio ffcommon.FInt64T = 0, 0
var ret ffcommon.FInt = 0
var i ffcommon.FUnsignedInt = 0
var h264bsfc, aacbsfc *libavcodec.AVBitStreamFilterContext
//打開輸入視訊檔案
ret = libavformat.AvformatOpenInput(&ifmtCtxVideo, inFilenameVideo, nil, nil)
if ret < 0 {
fmt.Printf("can't open input video file\n")
goto end
}
//查找輸入流
ret = ifmtCtxVideo.AvformatFindStreamInfo(nil)
if ret < 0 {
fmt.Printf("failed to retrieve input video stream information\n")
goto end
}
//打開輸入音頻檔案
ret = libavformat.AvformatOpenInput(&ifmtCtxAudio, inFilenameAudio, nil, nil)
if ret < 0 {
fmt.Printf("can't open input audio file\n")
goto end
}
//查找輸入流
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")
//建立輸出上下文
libavformat.AvformatAllocOutputContext2(&ofmtCtx, nil, "", outFilename)
if ofmtCtx == nil {
fmt.Printf("can't create output context\n")
goto end
}
//視訊輸入流
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.Index
if libavcodec.AvcodecParametersCopy(outStream.Codecpar, inStream.Codecpar) < 0 {
fmt.Printf("faild to copy context from input to output stream")
goto end
}
outStream.Codecpar.CodecTag = 0
break
}
}
//音頻輸入流
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.Index
if libavcodec.AvcodecParametersCopy(outStream.Codecpar, inStream.Codecpar) < 0 {
fmt.Printf("faild to copy context from input to output stream")
goto end
}
outStream.Codecpar.CodecTag = 0
break
}
}
fmt.Printf("==========Output Information==========\n")
ofmtCtx.AvDumpFormat(0, outFilename, 1)
fmt.Printf("======================================\n")
//打開輸入檔案
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
}
}
//寫檔案頭
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.AVFormatContext
var inStream, outStream *libavformat.AVStream
var streamIndex ffcommon.FInt = 0
if libavutil.AvCompareTs(curPstVideo, ifmtCtxVideo.GetStream(uint32(inVideoIndex)).TimeBase, curPstAudio, ifmtCtxAudio.GetStream(uint32(inAudioIndex)).TimeBase) < 0 {
ifmtCtx = ifmtCtxVideo
streamIndex = outVideoIndex
if 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 PTS
if packet.Pts == libavutil.AV_NOPTS_VALUE {
//write PTS
timeBase1 := inStream.TimeBase
//Duration between 2 frames
calcDuration := int64(libavutil.AV_TIME_BASE / libavutil.AvQ2d(inStream.RFrameRate))
//Parameters
packet.Pts = int64((float64(frameIndex) * float64(calcDuration)) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))
packet.Dts = packet.Pts
packet.Duration = int64(float64(calcDuration) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))
frameIndex++
}
curPstVideo = packet.Pts
break
}
if ifmtCtx.AvReadFrame(&packet) >= 0 {
} else {
break
}
}
} else {
break
}
} else {
ifmtCtx = ifmtCtxAudio
streamIndex = outAudioIndex
if 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 PTS
if packet.Pts == libavutil.AV_NOPTS_VALUE {
//write PTS
timeBase1 := inStream.TimeBase
//Duration between 2 frames
calcDuration := int64(libavutil.AV_TIME_BASE / libavutil.AvQ2d(inStream.RFrameRate))
//Parameters
packet.Pts = int64((float64(frameIndex) * float64(calcDuration)) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))
packet.Dts = packet.Pts
packet.Duration = int64(float64(calcDuration) / (libavutil.AvQ2d(timeBase1) * libavutil.AV_TIME_BASE))
frameIndex++
}
curPstAudio = packet.Pts
break
}
if ifmtCtx.AvReadFrame(&packet) >= 0 {
} else {
break
}
}
} else {
break
}
}
//FIX:Bitstream Filter
if 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/DTS
packet.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 = -1
packet.StreamIndex = uint32(streamIndex)
//write
if ofmtCtx.AvInterleavedWriteFrame(&packet) < 0 {
fmt.Printf("error muxing packet")
break
}
packet.AvPacketUnref()
}
//Write file trailer
ofmtCtx.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)
}
} 
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