2022-04-27：用 go 语言重写 ffmpeg 的 remuxing.c 示例。

go run ./examples/internalexamples/remuxing/main.go ./resources/big_buck_bunny.mp4 ./out/remuxing.flv./lib/ffplay ./out/remuxing.flv

package main
import (  "fmt"  "os"  "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")
func main0() (ret ffcommon.FInt) {  var ofmt *libavformat.AVOutputFormat  var ifmt_ctx, ofmt_ctx *libavformat.AVFormatContext  var pkt libavcodec.AVPacket  var in_filename, out_filename string  var i ffcommon.FInt  var stream_index ffcommon.FInt = 0  var stream_mapping *ffcommon.FInt  var stream_mapping_size ffcommon.FInt = 0
  if len(os.Args) < 3 {    fmt.Printf("usage: %s input output\nAPI example program to remux a media file with libavformat and libavcodec.\nThe output format is guessed according to the file extension.\n\n", os.Args[0])    return 1  }
  in_filename = os.Args[1]  out_filename = os.Args[2]
  ret = libavformat.AvformatOpenInput(&ifmt_ctx, in_filename, nil, nil)  if ret < 0 {    fmt.Printf("Could not open input file '%s'", in_filename)    goto end  }
  ret = ifmt_ctx.AvformatFindStreamInfo(nil)  if ret < 0 {    fmt.Printf("Failed to retrieve input stream information")    goto end  }
  ifmt_ctx.AvDumpFormat(0, in_filename, 0)
  libavformat.AvformatAllocOutputContext2(&ofmt_ctx, nil, "", out_filename)  if ofmt_ctx == nil {    fmt.Printf("Could not create output context\n")    ret = libavutil.AVERROR_UNKNOWN    goto end  }
  stream_mapping_size = int32(ifmt_ctx.NbStreams)  stream_mapping = (*int32)(unsafe.Pointer(libavutil.AvMalloczArray(uint64(stream_mapping_size), 4)))  if stream_mapping == nil {    ret = -libavutil.ENOMEM    goto end  }
  ofmt = ofmt_ctx.Oformat
  for i = 0; i < int32(ifmt_ctx.NbStreams); i++ {    var out_stream *libavformat.AVStream    in_stream := ifmt_ctx.GetStream(uint32(i))    in_codecpar := in_stream.Codecpar
    if in_codecpar.CodecType != libavutil.AVMEDIA_TYPE_AUDIO &&      in_codecpar.CodecType != libavutil.AVMEDIA_TYPE_VIDEO &&      in_codecpar.CodecType != libavutil.AVMEDIA_TYPE_SUBTITLE {      *(*int32)(unsafe.Pointer(uintptr(unsafe.Pointer(stream_mapping)) + uintptr(4*i))) = -1      continue    }
    *(*int32)(unsafe.Pointer(uintptr(unsafe.Pointer(stream_mapping)) + uintptr(4*i))) = stream_index    stream_index++
    out_stream = ofmt_ctx.AvformatNewStream(nil)    if out_stream == nil {      fmt.Printf("Failed allocating output stream\n")      ret = libavutil.AVERROR_UNKNOWN      goto end    }
    ret = libavcodec.AvcodecParametersCopy(out_stream.Codecpar, in_codecpar)    if ret < 0 {      fmt.Printf("Failed to copy codec parameters\n")      goto end    }    out_stream.Codecpar.CodecTag = 0  }  ofmt_ctx.AvDumpFormat(0, out_filename, 1)
  if ofmt.Flags&libavformat.AVFMT_NOFILE == 0 {    ret = libavformat.AvioOpen(&ofmt_ctx.Pb, out_filename, libavformat.AVIO_FLAG_WRITE)    if ret < 0 {      fmt.Printf("Could not open output file '%s'", out_filename)      goto end    }  }
  ret = ofmt_ctx.AvformatWriteHeader(nil)  if ret < 0 {    fmt.Printf("Error occurred when opening output file\n")    goto end  }
  for {    var in_stream, out_stream *libavformat.AVStream
    ret = ifmt_ctx.AvReadFrame(&pkt)    if ret < 0 {      break    }
    in_stream = ifmt_ctx.GetStream(pkt.StreamIndex)    if pkt.StreamIndex >= uint32(stream_mapping_size) ||      *(*int32)(unsafe.Pointer(uintptr(unsafe.Pointer(stream_mapping)) + uintptr(4*pkt.StreamIndex))) < 0 {      pkt.AvPacketUnref()      continue    }
    pkt.StreamIndex = uint32(*(*int32)(unsafe.Pointer(uintptr(unsafe.Pointer(stream_mapping)) + uintptr(4*pkt.StreamIndex))))    out_stream = ofmt_ctx.GetStream(pkt.StreamIndex)    log_packet(ifmt_ctx, &pkt, "in")
    /* copy packet */    pkt.Pts = libavutil.AvRescaleQRnd(pkt.Pts, in_stream.TimeBase, out_stream.TimeBase, libavutil.AV_ROUND_NEAR_INF|libavutil.AV_ROUND_PASS_MINMAX)    pkt.Dts = libavutil.AvRescaleQRnd(pkt.Dts, in_stream.TimeBase, out_stream.TimeBase, libavutil.AV_ROUND_NEAR_INF|libavutil.AV_ROUND_PASS_MINMAX)    pkt.Duration = libavutil.AvRescaleQ(pkt.Duration, in_stream.TimeBase, out_stream.TimeBase)    pkt.Pos = -1    log_packet(ofmt_ctx, &pkt, "out")
    ret = ofmt_ctx.AvInterleavedWriteFrame(&pkt)    if ret < 0 {      fmt.Printf("Error muxing packet\n")      break    }    pkt.AvPacketUnref()  }
  ofmt_ctx.AvWriteTrailer()end:
  libavformat.AvformatCloseInput(&ifmt_ctx)
  /* close output */  if ofmt_ctx != nil && ofmt.Flags&libavformat.AVFMT_NOFILE == 0 {    libavformat.AvioClosep(&ofmt_ctx.Pb)  }  ofmt_ctx.AvformatFreeContext()
  libavutil.AvFreep(uintptr(unsafe.Pointer(&stream_mapping)))
  if ret < 0 && ret != libavutil.AVERROR_EOF {    fmt.Printf("Error occurred: %s\n", libavutil.AvErr2str(ret))    return 1  }
  return 0}
func log_packet(fmt_ctx *libavformat.AVFormatContext, pkt *libavcodec.AVPacket, tag string) {  time_base := &fmt_ctx.GetStream(pkt.StreamIndex).TimeBase
  fmt.Printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",    tag,    libavutil.AvTs2str(pkt.Pts), libavutil.AvTs2timestr(pkt.Pts, time_base),    libavutil.AvTs2str(pkt.Dts), libavutil.AvTs2timestr(pkt.Dts, time_base),    libavutil.AvTs2str(pkt.Duration), libavutil.AvTs2timestr(pkt.Duration, time_base),    pkt.StreamIndex)}
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    }  }
  main0()}