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• Does anyone use go-av to parse mp4 audio and then use oto/portaudio to output it ?

  27 juillet 2021, par seven

  it is use go-av to get audio

  


  func audio() (<-chan []byte, error) {
    buffer := make(chan []byte, 1024)
    go func() {
     ......
      for inCtx.AvReadFrame(pkt) >= 0 {
            if pkt.StreamIndex() == audioStreamIndex {
                l := pCodecCtx.AvcodecDecodeAudio4((*avcodec.Frame)(unsafe.Pointer(utilFrame)), &gotName, pkt)
                //fmt.Println("AvcodecDecodeAudio4:", l)
                if l < 0 {
                    fmt.Println("codec decode audio4 error")
                    os.Exit(1)
                }
                if gotName > 0 {

                    fram := getFramBytes(utilFrame)
                    fmt.Println("buf add:", index)
                    buffer <- fram

                }
            }
            pkt.AvFreePacket()
        }
        go func() {
            for {
                if len(buffer) <= 0 {
                    fmt.Println("close buf")
                    close(buffer)
                    break
                }
            }
        }()

        (*avcodec.Context)(unsafe.Pointer(pCodecCtxOrig)).AvcodecClose()
    }()
    return buffer, nil
}
func getFramBytes(f *avutil.Frame) []byte {
    data := avutil.Data(f)
    var bf = make([]byte, len(data))
    for i := 0; i < len(data); i++ {

        if data[i] != nil {
            bf = append(bf, *data[i])
        }
    }
    return bf
}



  


  and it is output it

  


  func main() {

    portaudio.Initialize()
    defer portaudio.Terminate()
    out := make([]int32, 8192)
    stream, err := portaudio.OpenDefaultStream(0, 1, 44100, len(out), &out)
    defer stream.Close()
    if err != nil {
        fmt.Println(err)
        return
    }
    err = stream.Start()
    if err != nil {
        fmt.Println(err)
        return
    }
    defer stream.Stop()
    buf, err := audio()
    if err != nil {
        fmt.Println(err)
        return
    }
    //index := 0
    //c, err := oto.NewContext(44100, 2, 2, 8192)
    //if err != nil {
    //  return
    //}
    //defer c.Close()
    //
    //p := c.NewPlayer()
    //defer p.Close()
    for {
        select {
        case frame, ok := <-buf:
            if !ok {
                os.Exit(0)
            }
            //index += 1
            //fmt.Println("$$:", index)
            //if _, err := io.Copy(p, bytes.NewReader(frame)); err != nil {
            //  fmt.Println(err)
            //  return
            //}
            err := binary.Read(bytes.NewReader(frame), binary.BigEndian, out)
            if err != nil {
                fmt.Println("binary.Read:", err)
                os.Exit(0)
            }
            err = stream.Write()
            if err != nil {
                fmt.Println("stream.Write:", err)
                os.Exit(0)
            }
        }
    }

}



  


  ** the result is**

  


  binary.Read : unexpected EOF

  


  if use oto it has no effect

  


  Has anyone used this method, or is there any other way to use go-av to play audio and video ?

  


  Is there a problem in use ? I feel that there is a problem with the data conversion from the audio decoding.

  


  Maybe there is a problem with getFramBytes

  


• OpenCV3 returning float FRAME_COUNT

  15 mars 2016, par mprat

  I am using OpenCV3 on OSX with Python 2.7 bindings. However, when I try to read the frame count of my video (a .mp4 video), it returns a float - I am expecting an int. Do I need to compile OpenCV3 with some special flags ? Am I missing some codecs ?

  import cv2
  
  vid = cv2.VideoCapture("vid.mp4")
  
  print vid.get(cv2.CAP_PROP_FRAME_WIDTH)

  And it returns a float.

  Installation details :

  • ffmpeg : brew install ffmpeg --with-dcadec --with-openh264 --with-openjpeg --with-openssl --with-tools --with-x265  --with-zimg --with-libvidstab --with-libvpx
  • opencv3 : brew install opencv3 --with-ffmpeg --with-contrib

• Adding text to movie using ffmpeg

  23 août 2014, par microspace

  I use git to track *.ass subtitle files.
  Here is example of *.ass file :

  [Script Info]
  
  ; Script generated by Aegisub 3.1.2
  
  ; http://www.aegisub.org/
  
  Title: Default Aegisub file
  
  ScriptType: v4.00+
  
  
  
  [V4+ Styles]
  
  Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour,    BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
  
  Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,0,0,0,0,100,100,0,0,1,2,2,2,10,10,10,1
  
  Style: titr,DejaVu     
  
  
  
  Sans,20,&H007DDBFA,&H000000FF,&H00000000,&HFF000000,0,0,0,0,100,100,0,0,1,2,2,1,10,10,10,1
  
  
  
  [Events]
  
  Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
  
  Dialogue: 0,0:00:00.46,0:00:11.22,Default,,0,0,0,,Если это можно было бы
  
  Dialogue: 0,0:00:03.44,0:00:08.96,titr,,0,0,0,,{\pos(20,240)\fad(600,600)}бывший министр

  After commit I burn subtitles into video :

  ffmpeg -i video.avi -vf "ass=subtitle.ass" out.avi

  My goal is to show commit date for 10 second at the start of movie. This should be done automatically.

  1) It can be easily done with by modifying subtitle.ass itself, but I can’t do it after commit and there are other reasons.

  2) It can be done by ffmpeg from command line : How to use ffmpeg to add a text to avi video ?

  Problem is that in this case text will be shown for the whole lenght of movie.

  3) I can copy *.ass file to temporary directory, insert date, render and delete *.ass file.

  Is there a simpler way ?