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• 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)

• Input area 0:0:1280:675 not within the padded area 0:0:1280:674 or zero-sized

  7 septembre 2020, par ottpeter

  I'm setting a padding to a list of videos. When resolution was 854x480, it worked, when I switched to 1280x720 it does not work. Most likely this is because of odd numbers, as stated in this question : FFmpeg pad filter calculating wrong width

  


  This was my original code (bash script creating the filter complex parts) :

  


  # Resolution
RES_X=1280
RES_Y=720
...
FILTER_COMPLEX_LIST="${FILTER_COMPLEX_LIST}[$i:v]scale=$RES_X:$RES_Y:force_original_aspect_ratio=1,pad=width=$RES_X:height=$RES_Y:x='if(lt(in_w,$RES_X),($RES_X-in_w)/2,0)':0,setsar=1[v$i];"


  


  I changed the calculation of pad width and pad height, but the error is the same.

  


  FILTER_COMPLEX_LIST="${FILTER_COMPLEX_LIST}[$i:v]scale=$RES_X:$RES_Y:force_original_aspect_ratio=1,pad=width=ceil($RES_X/2)*2:height=ceil($RES_Y/2)*2:x='if(lt(in_w,$RES_X),($RES_X-in_w)/2,0)':0,setsar=1$


  


  This is the error :

  


  


  [Parsed_pad_19 @ 0x558b4fe3bb40] Input area 0:0:1280:675 not within
the padded area 0:0:1280:674 or zero-sized [Parsed_pad_19 @
0x558b4fe3bb40] Failed to configure input pad on Parsed_pad_19 Error
configuring complex filters. Invalid argument

  


  


  I don't understand why padded area is not padded area 0:0:1280:720 in the first place.
Where should I add the ceil() or floor() function to make this work ?

  


• How do I use ffmpeg in my renderer process in electron ?

  16 juillet 2023, par Infinibyte

  I'm trying to use ffmpeg in my renderer process in my electron app. I expose the modules in my preload.js file like this :

  


  const { contextBridge, ipcRenderer } = require('electron');
const ffmpegStatic = require('ffmpeg-static');
const ffmpeg = require('fluent-ffmpeg');
// make ffmpeg available as a function in the renderer process
contextBridge.exposeInMainWorld('ffmpeg', () => ffmpeg(ffmpegStatic.path));


  


  And I try to acces it in my renderer.js file like this :

  


  video.addEventListener('change', (event) => {
    const file = event.target.files[0];
    const filePath = file.path;
    const fileName = file.name;
    const fileExt = fileName.split('.').pop();
    const newFileName = fileName.replace(fileExt, 'mp4');
    const newFilePath = filePath.replace(fileName, newFileName);

    // Run FFmpeg
    ffmpeg()

        // Input file
        .input(filePath)

        // Audio bit rate
        .outputOptions('-ab', '192k')

        // Output file
        .saveToFile(newFilePath)

        // Log the percentage of work completed
        .on('progress', (progress) => {
            if (progress.percent) {
                console.log(`Processing: ${Math.floor(progress.percent)}% done`);
            }
        })

        // The callback that is run when FFmpeg is finished
        .on('end', () => {
            console.log('FFmpeg has finished.');
        })

        // The callback that is run when FFmpeg encountered an error
        .on('error', (error) => {
            console.error(error);
        });
});


  


  But then I get following error in the console : Uncaught TypeError : ffmpeg(...).input is not a function at HTMLInputElement.
I really don't know how to fix this, can anyone help me ?

  


  I tried writing it differently and defining ffmpeg in my rendere.js but nothing worked...