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• Does MPEG-Dash live have ?begin parameter in their URI to start playback from a particular position

  26 février 2023, par Raghavendra Ganiga

  I have a MPEG-DASH URI like below

  


  https://test.com/default/index.mpd?begin=20230222T120430

  


  where i have begin parameter specifying from where to start the playback. This is a dynamic MPD.

  


  I want to know is begin parameter a standard parameter of MPEG-DASH. If yes, then in which document this parameter is specified.

  


• FFplay only plays MPEG-DASH when in the same directory

  26 mars 2020, par M. Parker

  I’ve created a series of video segments using dashenc.c from ffmpeg’s libav on my windows machine. The mpd file is templated, so it’s fairly simple and it passes validation. The video plays, but only if I put ffplay in the same folder as all the files and use :

  ffplay -i manifest.mpd

  If I try to play from some other directory, or even the same directory using :

  ffplay -i c:\tmp\manifest.mpd

  or

  ffplay -i c:/tmp/manifest.mpd

  The attempt fails, producing this error :

  [dash @ 0000016ce0d69900] Failed to open an initialization section in playlist 0
  
  [dash @ 0000016ce0d69900] Error when loading first fragment, playlist 0
  
  C:/tmp/manifest.mpd: Invalid argument

  The mpd file :

  <?xml version="1.0" encoding="utf-8"?>
  
  <mpd xmlns="urn:mpeg:dash:schema:mpd:2011" profiles="urn:mpeg:dash:profile:isoff-live:2011" type="dynamic" minimumupdateperiod="PT500S" suggestedpresentationdelay="PT4S" availabilitystarttime="2020-03-23T14:54:16Z" publishtime="2020-03-23T14:54:25Z" timeshiftbufferdepth="PT4811H53M52.3S" minbuffertime="PT9.6S">
  
      <programinformation>
  
      </programinformation>
  
      <period start="PT0.0S">
  
          <adaptationset contenttype="video" segmentalignment="true" bitstreamswitching="true">
  
              <representation mimetype="video/mp4" codecs="avc1.42001e" bandwidth="5953124" width="720" height="480">
  
                  <segmenttemplate timescale="1000000" duration="5000000" availabilitytimeoffset="4.967" initialization="init-stream$RepresentationID$.m4s" media="media-stream$RepresentationID$-$Number%06d$.m4s" startnumber="1">
  
                  </segmenttemplate>
  
              </representation>
  
          </adaptationset>
  
      </period>
  
  </mpd>

  Adding in a BaseUrl element didn’t help ; my guess is I’m formatting it wrong. Any ideas what I might do to fix this ?

• 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 ?