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• System.Diagnostics.Process pipe (vertical bar) not accepted as argument

  28 septembre 2019, par emp

  I’m trying to execute this code using System.Diagnostics.Process. It works fine in command line. But in C# it’s failing on the | character.

  var myProcess = new Process();
  
  var p = new ProcessStartInfo();
  
  
  
  var sArgs = " -i emp.mp3 -f wav - | neroAacEnc -ignorelength -q 0.5 -if - -of emp.mp4";
  
  p.FileName = "ffmpeg.exe";
  
  p.CreateNoWindow = false;
  
  p.RedirectStandardOutput = false;
  
  p.UseShellExecute = false;
  
  p.Arguments = sArgs;
  
  
  
  myProcess.StartInfo = p;
  
  
  
  myProcess.Start();
  
  myProcess.WaitForExit();

  It gives the following error :

  Unable to find a suitable output format for ’|’ : Invalid argument

  I’ve looked around on stackoverflow and found the following hint but it is also not working :

  var psi = new ProcessStartInfo("ffmpeg.exe");
  
  psi.Arguments = 
  
      "\"-i emp.mp3 -f wav -\" | \"neroAacEnc -ignorelength -q 0.5 -if - -of emp.mp4\"";
  
  psi.CreateNoWindow = false;
  
  psi.UseShellExecute = false;
  
  
  
  var process = new Process { StartInfo = psi };
  
  
  
  process.Start();
  
  process.WaitForExit();

  gives the following error :

  Unrecognized option ’i emp.mp3 -f wav -’
  Failed to set value ’|’ for option ’i emp.mp3 -f wav -’

• How to correctly calculate which segments are ready to be downloaded using MPEG-DASH

  24 avril 2019, par igal k

  What i’m trying to do ?

  Write a simple MPEG-DASH client using the SegmentTemplate pattern to calculate which segments are ready to be downloaded for a live source.

  A picture taken using chrome’s debugging tools at a moment X showing an mpd request(8af651fd747.....mpd) and the actual segments fetched respectfully to that request.

  

  Given the following MPD

  <mpd availabilitystarttime="2019-04-24T06:43:32Z" maxsegmentduration="PT4.096S" minbuffertime="PT4.096S" minimumupdateperiod="PT15.835S" profiles="urn:mpeg:dash:profile:isoff-live:2011" publishtime="2019-04-24T11:14:01Z" suggestedpresentationdelay="PT11.878S" timeshiftbufferdepth="PT65.536S" type="dynamic" xmlns="urn:mpeg:dash:schema:mpd:2011">
  
    <location>https://content-aaps1.uplynk.com/channel/8af651fd7473474f86a05ffb0a1c8972.mpd?rmt=wv&amp;amp;cid=8af651fd7473474f86a05ffb0a1c8972&amp;amp;oid=600e5c27541344a1bf3818617ad712ce&amp;amp;prettydash=1&amp;amp;exp=1556091088&amp;amp;rn=4138683939&amp;amp;tc=1&amp;amp;ct=c&amp;amp;sig=5fb7f0c18f3f1d2ad4fdee53c02c1e1ed904bc5e8474f4ebf886d209ff7f21c9&amp;amp;pbs=05b6594bcf4b4728ac1094976a80194d</location>
  
    <period start="PT2826.240S">
  
      <adaptationset maxframerate="30" maxheight="720" maxwidth="1280" mimetype="video/mp4" segmentalignment="true" startwithsap="1">
  
        <representation bandwidth="2604473" codecs="avc1.64001e" framerate="30" height="360" scantype="progressive" width="640">
  
          <baseurl>https://x-default-stgec.uplynk.com/aapm/slices/8c1/600e5c27541344a1bf3818617ad712ce/8c1027496a964b049f1bd5895f8f0412/</baseurl>
  
          <segmenttemplate duration="368640" initialization="https://x-default-stgec.uplynk.com/aapm/slices/8c1/600e5c27541344a1bf3818617ad712ce/8c1027496a964b049f1bd5895f8f0412/$RepresentationID$_init.mp4?pbs=05b6594bcf4b4728ac1094976a80194d&amp;amp;_jt=l&amp;amp;chid=8af651fd7473474f86a05ffb0a1c8972" media="$RepresentationID$$Number%08d$.m4f?pbs=05b6594bcf4b4728ac1094976a80194d&amp;amp;_jt=l&amp;amp;chid=8af651fd7473474f86a05ffb0a1c8972" presentationtimeoffset="254361599" startnumber="690" timescale="90000"></segmenttemplate>
  
        </representation>
  
      </adaptationset>
  
    </period>
  
    <utctiming schemeiduri="urn:mpeg:dash:utc:http-iso:2014" value="https://content-aaps1.uplynk.com/misc/utcservertime"></utctiming>
  
  </mpd>

  I see that the next segment request should be #3955

  What i have tried so far

      period.end = 1556104456;
  
      period.start = 2826;
  
      availability_start_time = 1556088212;
  
      max_segment_duration = 4;
  
      time_shift_buffer_depth = 65

  So, first of all, i read DASH-IF-IOP 4.3 section 4.3.4.2 page #82 and implemented the following code :

     int k1 = 1;
  
  int period_duration = period.end - (period.start + data_.availability_start_time);
  
  int k2 = ceil((float)period_duration / (float)data_.max_segment_duration);
  
  double duration = ((float)representation.duration / (float)representation.timeScale);
  
  size_t live_edge = std::min(
  
      (int)floor((float)((data_.publish_time - data_.availability_start_time - period.start) / duration)), k2);
  
  
  
  size_t oldest = std::max(k1, (int)floor((float)((data_.publish_time - data_.availability_start_time - period.start -
  
                                                      data_.time_shift_buffer_depth) /
  
                                                  duration)));

  after calculating everything : k1=1, k2=3355, live_edge=3272 and oldest=3256

  Also tried using ffmpeg’s dashdec.c

  for min_segment :

  if (c->is_live && pls->fragment_duration)
  
      {
  
          num = pls->first_seq_no + (((get_current_time_in_sec() - c->availability_start_time) - c->time_shift_buffer_depth) * pls->fragment_timescale) / pls->fragment_duration;
  
      }

  for max_segment :

  num = pls->first_seq_no + (((get_current_time_in_sec() - c->availability_start_time)) * pls->fragment_timescale) / pls->fragment_duration;

  after a small modification :

  size_t pmax = (((data_.publish_time - data_.availability_start_time))) / duration;
  
  size_t pmin = ((data_.publish_time - data_.availability_start_time) - data_.time_shift_buffer_depth) / duration;

  pmin=3946 pmax=3961

  in the ffmpeg example, i had to manually remove the first_seq_no variable because it looked like i doubled added the SegmentTemplate@StartNumber.

  even after succeeding in this task, how do i exactly build the request list of Segment(NOW) ----> Segment(LIVE_EDGE)

• Shaka Player : ignore empty AdaptationSet

  24 juin 2019, par Mitya

  I’m trying to play DASH stream in Shaka Player.
  Sometimes the stream doesn’t have an audio source and its manifest file contains an empty AdaptationSet entry.
  In this case Shaka Player returns the manifest parsing error :

  | DASH_EMPTY_ADAPTATION_SET | 4003 | number |  The DASH Manifest contained an AdaptationSet with no Representations. |

  Is it possible to ignore this error somehow and play the video without audio source ?

  Example of manifest 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="PT4S" suggestedpresentationdelay="PT4S" availabilitystarttime="2019-06-24T13:38:04Z" publishtime="2019-06-24T13:38:34Z" timeshiftbufferdepth="PT14.9S" minbuffertime="PT9.9S">
  
      <programinformation>
  
          
  
      </programinformation>
  
      <period start="PT0.0S">
  
          <adaptationset contenttype="video" segmentalignment="true" bitstreamswitching="true">
  
              <representation mimetype="video/mp4" codecs="avc1.640028" bandwidth="2000000" width="1920" height="1080" framerate="20/1">
  
                  <segmenttemplate timescale="10240" initialization="init-stream$RepresentationID$.m4s" media="chunk-stream$RepresentationID$-$Number%05d$.m4s" startnumber="5">
  
                      <segmenttimeline>
  
                          <s t="201697" d="51190" r="2"></s>
  
                      </segmenttimeline>
  
                  </segmenttemplate>
  
              </representation>
  
          </adaptationset>
  
          <adaptationset contenttype="audio" segmentalignment="true" bitstreamswitching="true">
  
          </adaptationset>
  
      </period>
  
  </mpd>