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• exec.Command error, no output to stdout or stderr

  19 février 2019, par n3wton

  I am trying to get the duration of a video using ffprobe and exec.Command but I keep getting an error. However, stdout and stderr are both empty so I don’t know what the problem is.

  func getVideoLength(filename string) float64 {
  
  cmd := exec.Command("ffprobe", "-i", filename, "-show_entries", "format=duration", "-v", "quiet", "-of", "csv=\"p=0\"")
  
  fmt.Println("ffprobe", "-i", filename, "-show_entries", "format=duration", "-v", "quiet", "-of", "csv=\"p=0\"")
  
      var out bytes.Buffer
  
      var stderr bytes.Buffer
  
      cmd.Stdout = &out
  
      cmd.Stderr = &stderr
  
      err := cmd.Run()
  
      if err != nil {
  
          fmt.Println("out: " + out.String())
  
          fmt.Println("stderr: " + stderr.String())
  
          log.Fatal(err)
  
      }
  
  
  
      length, err := strconv.ParseFloat(out.String(), 64)
  
      if err != nil {
  
          log.Fatal(err)
  
      }
  
  
  
  return length
  
  }

  Here is the output I get :

  ffprobe -i amelie.mp4 -show_entries format=duration -v quiet -of csv="p=0"
  
  out: 
  
  stderr: 
  
  2019/02/18 21:04:39 exit status 1

  not very helpful.

  Any ideas ?. Thanks.

• Adaptive part in MPD using MP4box

  28 janvier 2019, par enigmaVada

  I have used ffmpeg to encode audio and video files of my video sample.mp4 for the dash player. The commands are as follows :

  ffmpeg -i sample.mp4 -s 426x240 -c:v libx264 -b:v 640k -g 90 -an sample_video_240.mp4
  
  ffmpeg -i sample.mp4 -s 480x360 -c:v libx264 -b:v 960k -g 90 -an sample_video_360.mp4
  
  ffmpeg -i sample.mp4 -s 640x480 -c:v libx264 -b:v 1280k -g 90 -an sample_video_480.mp4
  
  ffmpeg -i sample.mp4 -s 1280x720 -c:v libx264 -b:v 2560k -g 90 -an sample_video_720.mp4
  
  
  
  ffmpeg -i sample.mp4 -c:a aac -b:a 128k -vn sample_audio.mp4

  I have generated 240p,360p,480p and 720p videos and audio file.

  Then I have used mp4box to generate the mpd file using the following command :

  mp4box -dash 10000 -rap -profile dashavc264:onDemand -mpd-title BBB -out sample.mpd -frag 5000 sample_audio.mp4 sample_video_240.mp4 sample_video_360.mp4 sample_video_480.mp4 sample_video_720.mp4 

  I am using the dash.js player to play the video. The problem is, the adaptive part of DASH isn’t working. The player is just using the 240p video and not switching to a better format even if proper bandwidth is available. I am checking using the network tab of chrome dev tools.

  What am i doing wrong ? Please help.

  Here is the mpd file for reference :

  <?xml version="1.0"?>
  
  
  
  <mpd xmlns="urn:mpeg:dash:schema:mpd:2011" minbuffertime="PT1.500S" type="static" mediapresentationduration="PT0H1M9.869S" maxsegmentduration="PT0H0M9.985S" profiles="urn:mpeg:dash:profile:isoff-on-demand:2011,http://dashif.org/guidelines/dash264">
  
   <programinformation moreinformationurl="http://gpac.io">
  
    
  
   </programinformation>
  
  
  
   <period duration="PT0H1M9.869S">
  
    <adaptationset segmentalignment="true" lang="und" subsegmentalignment="true" subsegmentstartswithsap="1">
  
     <representation mimetype="audio/mp4" codecs="mp4a.40.2" audiosamplingrate="44100" startwithsap="1" bandwidth="130920">
  
      <audiochannelconfiguration schemeiduri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"></audiochannelconfiguration>
  
      <baseurl>sample_audio_dashinit.mp4</baseurl>
  
      <segmentbase indexrangeexact="true" indexrange="902-1017">
  
        <initialization range="0-901"></initialization>
  
      </segmentbase>
  
     </representation>
  
    </adaptationset>
  
    <adaptationset segmentalignment="true" group="1" maxwidth="426" maxheight="240" maxframerate="30" par="426:240" lang="und" subsegmentalignment="true" subsegmentstartswithsap="1">
  
     <representation mimetype="video/mp4" codecs="avc1.640015" width="426" height="240" framerate="30" sar="1:1" startwithsap="1" bandwidth="590708">
  
      <baseurl>sample_video_240_dashinit.mp4</baseurl>
  
      <segmentbase indexrangeexact="true" indexrange="914-1053">
  
        <initialization range="0-913"></initialization>
  
      </segmentbase>
  
     </representation>
  
    </adaptationset>
  
    <adaptationset segmentalignment="true" group="1" maxwidth="640" maxheight="480" maxframerate="30" par="4:3" lang="und" subsegmentalignment="true" subsegmentstartswithsap="1">
  
     <representation mimetype="video/mp4" codecs="avc1.64001E" width="480" height="360" framerate="30" sar="1:1" startwithsap="1" bandwidth="883873">
  
      <baseurl>sample_video_360_dashinit.mp4</baseurl>
  
      <segmentbase indexrangeexact="true" indexrange="914-1053">
  
        <initialization range="0-913"></initialization>
  
      </segmentbase>
  
     </representation>
  
     <representation mimetype="video/mp4" codecs="avc1.64001E" width="640" height="480" framerate="30" sar="1:1" startwithsap="1" bandwidth="1188712">
  
      <baseurl>sample_video_480_dashinit.mp4</baseurl>
  
      <segmentbase indexrangeexact="true" indexrange="913-1052">
  
        <initialization range="0-912"></initialization>
  
      </segmentbase>
  
     </representation>
  
    </adaptationset>
  
    <adaptationset segmentalignment="true" group="1" maxwidth="1280" maxheight="720" maxframerate="30" par="16:9" lang="und" subsegmentalignment="true" subsegmentstartswithsap="1">
  
     <representation mimetype="video/mp4" codecs="avc1.64001F" width="1280" height="720" framerate="30" sar="1:1" startwithsap="1" bandwidth="2365717">
  
      <baseurl>sample_video_720_dashinit.mp4</baseurl>
  
      <segmentbase indexrangeexact="true" indexrange="914-1053">
  
        <initialization range="0-913"></initialization>
  
      </segmentbase>
  
     </representation>
  
    </adaptationset>
  
   </period>
  
  </mpd>

• Does ffmpeg support 7.x channels encoding in Dolby Digital format (.ac3) ?

  4 novembre 2019, par CC2023

  Using ffmpeg, I was able to encode 5.x channels from .wav to .ac3. But 7.x channels did not work. The encoded .ac3 missed channel 6th and 7th.

  Does ffmpeg support 7.x channel encoding for .ac3 ?

  My ffmpeg version git-2019-10-28-68f623d. Thanks.