2023-03-23：音视频解混合（demuxer）为PCM和YUV420P，用go语言编写。
答案2023-03-23：
大体步骤如下：
1.打开媒体文件，并获取音频和视频流。
2.对于每个流，找到对应的解码器、创建解码上下文并打开解码器。
3.一帧一帧读取压缩的音频或视频数据AVPacket，并调用对应的解码器进行解码。
4.对于音频：重采样成16bit 44100 PCM格式，并将数据写入输出文件或缓冲区。
5.对于视频：转换成YUV420P格式，并将数据写入输出文件或缓冲区。
6.清理已分配的资源。
代码见github/moonfdd/ffmpeg-go库。
执行命令：
go run ./examples/a23.video_demuxer_mp42yuvpcm/main.go
代码参考23：音视频解混合（demuxer）为PCM和YUV420P，代码如下：
// https://feater.top/ffmpeg/ffmpeg-demuxer-video-to-pcm-and-yuv420
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/libavdevice"
"github.com/moonfdd/ffmpeg-go/libavformat"
"github.com/moonfdd/ffmpeg-go/libavutil"
"github.com/moonfdd/ffmpeg-go/libswresample"
"github.com/moonfdd/ffmpeg-go/libswscale"
)
/*
* 音频播放命令：ffplay -ar 44100 -ac 1 -f s16le -i out.pcm
*/
const i44100 = 22050
func avcodec_save_audio_file(pFormatCtx *libavformat.AVFormatContext, streamIndex ffcommon.FInt, fileName string) ffcommon.FInt {
var pCodec *libavcodec.AVCodec
var pCodecCtx *libavcodec.AVCodecContext
codecpar := pFormatCtx.GetStream(uint32(streamIndex)).Codecpar
//4.获取解码器（一）:音频
//根据索引拿到对应的流
pCodec = libavcodec.AvcodecFindDecoder(codecpar.CodecId)
if pCodec == nil {
fmt.Printf("can't decoder audio\n")
return -1
}
//申请一个解码上下文
pCodecCtx = pCodec.AvcodecAllocContext3()
if pCodecCtx == nil {
fmt.Printf("can't allocate a audio decoding context\n")
return -1
}
//用流解码信息初始化编码参数
pCodecCtx.AvcodecParametersToContext(codecpar)
//没有此句会出现：Could not update timestamps for skipped samples
pCodecCtx.PktTimebase = pFormatCtx.GetStream(uint32(streamIndex)).TimeBase
//5.打开解码器
if pCodecCtx.AvcodecOpen2(pCodec, nil) < 0 {
fmt.Printf("can't open codec\n")
return -1
}
// printf("--------------- File Information ----------------\n");
// av_dump_format(pFormatCtx, 0, fileName, 0);
// printf("-------------------------------------------------\n");
//编码数据
packet := new(libavcodec.AVPacket)
//解压缩数据
frame := libavutil.AvFrameAlloc()
//frame->16bit 44100 PCM统一音频采样格式与采样率
swrCtx := libswresample.SwrAlloc()
//重采样设置选项-----------------------------------------------------------start
//输入的采样格式
inSampleFmt := pCodecCtx.SampleFmt
//输出的采样格式
var outSampleFmt libswresample.AVSampleFormat = libavutil.AV_SAMPLE_FMT_S16
//输入的采样率
inSampleRate := pCodecCtx.SampleRate
//输出的采样率
var outSampleRate ffcommon.FInt = i44100
//输入的声道布局
var inChannelLayout ffcommon.FUint64T = pCodecCtx.ChannelLayout
//输出的声道布局：CHANNEL_IN_MONO为单声道，CHANNEL_IN_STEREO为双声道
var outChannelLayout ffcommon.FUint64T = libavutil.AV_CH_LAYOUT_MONO
fmt.Printf("inSampleFmt = %d, inSampleRate = %d, inChannelLayout = %d， name = %s\n", inSampleFmt, inSampleRate,
inChannelLayout, ffcommon.StringFromPtr(pCodec.Name))
swrCtx.SwrAllocSetOpts(int64(outChannelLayout), outSampleFmt, outSampleRate,
int64(inChannelLayout), inSampleFmt, inSampleRate, 0, uintptr(0))
swrCtx.SwrInit()
//重采样设置选项-----------------------------------------------------------end
//获取输出的声道个数
outChannelNb := libavutil.AvGetChannelLayoutNbChannels(outChannelLayout)
fmt.Printf("outChannelNb = %d\n", outChannelNb)
// //存储PCM数据
outBuffer := (*byte)(unsafe.Pointer(libavutil.AvMalloc(2 * i44100)))
// FILE *fp = fopen(fileName, "wb");
fp, _ := os.Create(fileName)
//回到流的初始位置
pFormatCtx.AvSeekFrame(streamIndex, 0, libavformat.AVSEEK_FLAG_BACKWARD)
//6.一帧一帧读取压缩的音频数据AVPacket
for pFormatCtx.AvReadFrame(packet) >= 0 {
if packet.StreamIndex == uint32(streamIndex) {
//解码AVPacket --> AVFrame
ret := pCodecCtx.AvcodecSendPacket(packet)
if ret < 0 {
fmt.Printf("Decode error\n")
break
}
if pCodecCtx.AvcodecReceiveFrame(frame) >= 0 {
swrCtx.SwrConvert(&outBuffer, 2*i44100, (**byte)(unsafe.Pointer(&frame.Data)), frame.NbSamples)
//获取sample的size
outBufferSize := libavutil.AvSamplesGetBufferSize(nil, outChannelNb, frame.NbSamples, outSampleFmt, 1)
//写入文件
fp.Write(ffcommon.ByteSliceFromByteP(outBuffer, int(outBufferSize)))
}
}
packet.AvPacketUnref()
}
fp.Close()
libavutil.AvFrameFree(&frame)
libavutil.AvFree(uintptr(unsafe.Pointer(outBuffer)))
libswresample.SwrFree(&swrCtx)
pCodecCtx.AvcodecClose()
return 0
}
/*
* 视频播放命令：ffplay -video_size 654x368 -i out.yuv
*/
func avcodec_save_video_file(pFormatCtx *libavformat.AVFormatContext, streamIndex ffcommon.FInt, fileName string) ffcommon.FInt {
var pCodec *libavcodec.AVCodec
var pCodecCtx *libavcodec.AVCodecContext
codecpar := pFormatCtx.GetStream(uint32(streamIndex)).Codecpar
//4.获取解码器（一）:音频
//根据索引拿到对应的流
pCodec = libavcodec.AvcodecFindDecoder(codecpar.CodecId)
if pCodec == nil {
fmt.Printf("can't decoder audio\n")
return -1
}
//申请一个解码上下文
pCodecCtx = pCodec.AvcodecAllocContext3()
if pCodecCtx == nil {
fmt.Printf("can't allocate a audio decoding context\n")
return -1
}
//用流解码信息初始化编码参数
pCodecCtx.AvcodecParametersToContext(codecpar)
//没有此句会出现：Could not update timestamps for skipped samples
pCodecCtx.PktTimebase = pFormatCtx.GetStream(uint32(streamIndex)).TimeBase
//5.打开解码器
if pCodecCtx.AvcodecOpen2(pCodec, nil) < 0 {
fmt.Printf("can't open codec\n")
return -1
}
// printf("--------------- File Information ----------------\n");
// av_dump_format(pFormatCtx, 0, fileName, 0);
// printf("-------------------------------------------------\n");
//编码数据
pPacket := new(libavcodec.AVPacket)
//解压缩数据
pFrame := libavutil.AvFrameAlloc()
pFrameYUV := libavutil.AvFrameAlloc()
outBuffer := (*byte)(unsafe.Pointer(libavutil.AvMalloc(
uint64(libavutil.AvImageGetBufferSize(libavutil.AV_PIX_FMT_YUV420P, pCodecCtx.Width, pCodecCtx.Height, 1)))))
libavutil.AvImageFillArrays((*[4]*byte)(unsafe.Pointer(&pFrameYUV.Data)), (*[4]int32)(unsafe.Pointer(&pFrameYUV.Linesize)), outBuffer,
libavutil.AV_PIX_FMT_YUV420P, pCodecCtx.Width,
pCodecCtx.Height, 1)
pImgConvertCtx := libswscale.SwsGetContext(pCodecCtx.Width, pCodecCtx.Height, pCodecCtx.PixFmt,
pCodecCtx.Width, pCodecCtx.Height, libavutil.AV_PIX_FMT_YUV420P, libswscale.SWS_BICUBIC, nil, nil, nil)
fmt.Printf("width = %d, height = %d, name = %s\n", pCodecCtx.Width, pCodecCtx.Height, ffcommon.StringFromPtr(pCodec.Name))
fp, _ := os.Create(fileName)
//回到流的初始位置
pFormatCtx.AvSeekFrame(streamIndex, 0, libavformat.AVSEEK_FLAG_BACKWARD)
//6.一帧一帧读取压缩的视频数据AVPacket
for pFormatCtx.AvReadFrame(pPacket) >= 0 {
if pPacket.StreamIndex == uint32(streamIndex) {
//解码AVPacket --> AVFrame
ret := pCodecCtx.AvcodecSendPacket(pPacket)
if ret < 0 {
fmt.Printf("Decode error\n")
break
}
if pCodecCtx.AvcodecReceiveFrame(pFrame) >= 0 {
pImgConvertCtx.SwsScale((**byte)(unsafe.Pointer(&pFrame.Data)), (*int32)(unsafe.Pointer(&pFrame.Linesize)), 0,
uint32(pCodecCtx.Height), (**byte)(unsafe.Pointer(&pFrameYUV.Data)), (*int32)(unsafe.Pointer(&pFrameYUV.Linesize)))
y_size := pCodecCtx.Width * pCodecCtx.Height
fp.Write(ffcommon.ByteSliceFromByteP(pFrameYUV.Data[0], int(y_size))) //Y
fp.Write(ffcommon.ByteSliceFromByteP(pFrameYUV.Data[1], int(y_size/4))) //U
fp.Write(ffcommon.ByteSliceFromByteP(pFrameYUV.Data[2], int(y_size/4))) //V
}
}
pPacket.AvPacketUnref()
}
fp.Close()
libavutil.AvFrameFree(&pFrame)
libavutil.AvFrameFree(&pFrameYUV)
libavutil.AvFree(uintptr(unsafe.Pointer(outBuffer)))
pCodecCtx.AvcodecClose()
return 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
}
}
inputFile := "./resources/big_buck_bunny.mp4"
outAudioFile := "./out/a23.pcm"
outVideoFile := "./out/a23.yuv"
var videoStreamIndex ffcommon.FInt = -1
var audioStreamIndex ffcommon.FInt = -1
var i ffcommon.FUnsignedInt = 0
var pFormatCtx *libavformat.AVFormatContext
//1.注册组件
libavdevice.AvdeviceRegisterAll()
//封装格式上下文
pFormatCtx = libavformat.AvformatAllocContext()
//2.打开输入文件
if libavformat.AvformatOpenInput(&pFormatCtx, inputFile, nil, nil) != 0 {
fmt.Printf("can't open input file\n")
return
}
//3.获取音视频信息
if pFormatCtx.AvformatFindStreamInfo(nil) < 0 {
fmt.Printf("can't find stream info\n")
return
}
//音视频编码，找到对应的音视频流的索引位置
//找到音频流的索引
for i = 0; i < pFormatCtx.NbStreams; i++ {
if pFormatCtx.GetStream(i).Codecpar.CodecType == libavutil.AVMEDIA_TYPE_AUDIO {
audioStreamIndex = int32(i)
break
}
}
//找到视频流的索引
for i = 0; i < pFormatCtx.NbStreams; i++ {
if pFormatCtx.GetStream(i).Codecpar.CodecType == libavutil.AVMEDIA_TYPE_VIDEO {
videoStreamIndex = int32(i)
break
}
}
fmt.Printf("audioStreamIndex = %d, videoStreamIndex = %d\n", audioStreamIndex, videoStreamIndex)
if audioStreamIndex == -1 {
fmt.Printf("can't find a audio stream\n")
} else {
fmt.Printf("try to save audio stream\n")
avcodec_save_audio_file(pFormatCtx, audioStreamIndex, outAudioFile)
}
if videoStreamIndex == -1 {
fmt.Printf("can't find a video stream\n")
} else {
fmt.Printf("try to save video stream\n")
avcodec_save_video_file(pFormatCtx, videoStreamIndex, outVideoFile)
}
libavformat.AvformatCloseInput(&pFormatCtx)
fmt.Println("-----------------------------------------")
go func() {
_, err = exec.Command("./lib/ffplay.exe", "-ar", "22050", "-ac", "1", "-f", "s16le", "-i", outAudioFile).Output()
if err != nil {
fmt.Println("play err = ", err)
}
}()
_, err = exec.Command("./lib/ffplay.exe", "-video_size", "640*360", "-i", outVideoFile).Output()
if err != nil {
fmt.Println("play err = ", err)
}
}
![[C#] FFmpeg 音视频开发总结](https://www.kunjuke.com/file/css/thumb/3.jpg/280-180.jpg)