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• How to convert mpeg-dash files back to mp4 or mkv via FFMPEG

  15 janvier 2017, par Saif Ullah

  Recently I tried downloading a video file via a program called "video cache view", it created two video files instead of one numbered as mpegdashtmp1.mp4 which are i guess in some mpeg-dash format. I searched about it and came to know that out of these two files one should contain the audio and the other will be the video part. How can I convert those files to mp4/mkv via FFMPEG.

• dash.js not playing mpd file generated by MP4Box

  9 mars 2016, par user3291299

  I have transcoded and stripped the audio of an mp4 file as follows :

  $ ffmpeg -codec:a libvo_aacenc -ar 44100 -ac 1 -codec:v libx264 -profile:v baseline -level 13 -b:v 2000k dir/out.mp4 -i dir/original.mp4

  $ ffmpeg -i dir/out.mp4 -an dir/out_an.mp4

  I’ve used the following MP4Box command to generate a mpd :

  $ MP4Box -dash 30000 -dash-profile on-demand -segment-name out-seg -out dir/out_dash dir/out.mp4

  This results in the following mpd file :

  <?xml version="1.0"?>
  
  
  
  <mpd xmlns="urn:mpeg:dash:schema:mpd:2011" minbuffertime="PT1.500000S" type="static" mediapresentationduration="PT0H2M11.77S" profiles="urn:mpeg:dash:profile:full:2011">
  
   <programinformation moreinformationurl="http://gpac.sourceforge.net">
  
    
  
   </programinformation>
  
  
  
   <period duration="PT0H2M11.77S">
  
    <adaptationset segmentalignment="true" maxwidth="640" maxheight="360" maxframerate="30000/1001" par="16:9">
  
     <contentcomponent contenttype="video" lang="und"></contentcomponent>
  
     <contentcomponent contenttype="audio" lang="und"></contentcomponent>
  
     <representation mimetype="video/mp4" codecs="avc1.42c00d,mp4a.40.02" width="640" height="360" framerate="30000/1001" sar="1:1" audiosamplingrate="44100" startwithsap="0" bandwidth="2097272">
  
      <audiochannelconfiguration schemeiduri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"></audiochannelconfiguration>
  
      <segmentlist timescale="1000" duration="30046">
  
       <initialization sourceurl="out-seginit.mp4"></initialization>
  
       <segmenturl media="out-seg1.m4s"></segmenturl>
  
       <segmenturl media="out-seg2.m4s"></segmenturl>
  
       <segmenturl media="out-seg3.m4s"></segmenturl>
  
       <segmenturl media="out-seg4.m4s"></segmenturl>
  
       <segmenturl media="out-seg5.m4s"></segmenturl>
  
      </segmentlist>
  
     </representation>
  
    </adaptationset>
  
   </period>
  
  </mpd>

• How to set segment duration of a DASH stream using ffmpeg ?

  25 juillet 2024, par ipartola

  I am trying to convert a video to a live DASH stream using ffmpeg. The command looks like this :

  


  ffmpeg -i input.mp4 -preset veryfast \
-c:v libx264 -pix_fmt yuv420p -map 0:v:0 \
-s:0 1280x720 -b:v:0 2M -maxrate:0 2.5M -bufsize:0 4M \
-use_template 1 -use_timeline 1 -seg_duration 1 -f dash foo/stream.mpd


  


  I would like to have the segment duration be 1 second long. However the above command seems to produce chunk files about 8 seconds long instead. However if I change the command to the following (adding -g 5) :

  


  ffmpeg -i input.mp4 -preset veryfast \
-c:v libx264 -pix_fmt yuv420p -map 0:v:0 \
-s:0 1280x720 -b:v:0 2M -maxrate:0 2.5M -bufsize:0 4M \
-g 5 \
-use_template 1 -use_timeline 1 -seg_duration 1 -f dash foo/stream.mpd


  


  I get chunk files that are much closer to 1 second long. Obviously this isn't ideal since that will produce a keyframe every 5 frames. So :

  


  a) I don't understand the relationship between seg_duration and keyframe interval. Why is ffmpeg not automatically just putting a keyframe at the beginning of each chunk ?

  


  b) How do I get the chunk/segment length I want ?