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• How to make a MPEG-DASH MPD which starts the playback in the middle of the first segment ?

  18 septembre 2018, par ravin.wang

  Here are the reproduce steps :

  1. Normalize an H.264 video stream

     ffmpeg -i 2.h264 -c:v libx264 -intra -r 25 -vf scale=640x360,setdar=16:9 2@25fps@intra@640x360.h264

     (*) After that, I got an H.264 stream where all pictures are H.264 IDR frames, and fps is 25, resolution is 640x360, aspect-ratio is 16:9.

  2. Generate an MP4 file

     MP4Box -add 2@25fps@intra@640x360.h264:timescale=1000 -fps 25 2@25fps@intra@640x360.mp4

  3. Make dash MP4 fragmented content, including init mp4, .m4s files and one .mpd file

     MP4Box -dash 5000 -frag 5000 -dash-scale 1000 -frag-rap -segment-name ’seg_second$Number$’ -segment-timeline -profile live 2@25fps@intra@640x360.mp4

  4. Copy and publish all these files to a folder under one HTTPD server

  5. I want to play from 4s of the first segment, and don’t display any frames before 4s, so I changed the .MPD file to modify the fields "SegmentTemplate@presentationTimeOffset", "SegmentTimeline:S@d/t", like as :
     

     <?xml version="1.0"?>
<mpd xmlns="urn:mpeg:dash:schema:mpd:2011" minbuffertime="PT1.500S" type="static" mediapresentationduration="PT0H0M26.000S" maxsegmentduration="PT0H0M5.000S" profiles="urn:mpeg:dash:profile:isoff-live:2011">
<period duration="PT0H0M26.000S">
<adaptationset segmentalignment="true" maxwidth="640" maxheight="360" maxframerate="25" par="16:9" lang="und">
 <segmenttemplate presentationtimeoffset="4000" media="seg_second$Number$.m4s" timescale="1000" startnumber="1" initialization="seg_secondinit.mp4">
   <segmenttimeline>
       <s d="1000" t="4000"></s>
       <s d="5000" r="4"></s>
   </segmenttimeline>
  </segmenttemplate>
<representation mimetype="video/mp4" codecs="avc3.64101E" width="640" height="360" framerate="25" sar="1:1" startwithsap="1" bandwidth="2261831">
</representation>
</adaptationset>
</period>
</mpd>

     
     

  6. Play the MPD url from VLC player, or Edge browser, it always starts the the first frame of the first segment, the frames between 0s 4s are also displayed unexpectedly.

  What’s wrong with my steps ? Or any other options for it ?

• mpeg-dash live streaming can't fetch chunks

  27 juin 2020, par user1902653

  I'm trying to create a live stream of mpeg-dash with ffmpeg.

  


  I'm streaming with python the frames to the ffmpeg process.

  


  This is the current command I'm using for creating the mpeg-dash manifest and m4s files :

  


  ffmpeg -re -f rawvideo -pix_fmt bgr24 -video_size 640x360 -i - -vcodec libx264 -preset ultrafast -tune zerolatency -f dash -window_size 10 -use_template 1 -use_timeline 0 -live 1 /srv/http/dash/stream.mpd


  


  I'm using nginx as a server for now and I've created a simple index.html using shaka player, but the problem is I couldn't get it to load and play more then the first chunk. (checked with dev-tools in chrome in the network tab)

  


  This is how I'm using shaka player right now :

  


  


  


  &#xA;    &#xA;        <code class="echappe-js">&lt;script src=&quot;https://cdnjs.cloudflare.com/ajax/libs/shaka-player/2.1.4/shaka-player.compiled.js&quot;&gt;&lt;/script&gt;&#xA;        &lt;script&gt;&amp;#xA;            var manifestUri = &amp;#x27;stream.mpd&amp;#x27;;&amp;#xA;            function initApp() {&amp;#xA;                shaka.polyfill.installAll();&amp;#xA;                if (shaka.Player.isBrowserSupported()) {&amp;#xA;                    initPlayer();&amp;#xA;                } else {&amp;#xA;                    console.error(&amp;#x27;Browser not supported!&amp;#x27;);&amp;#xA;                }&amp;#xA;            }&amp;#xA;            function initPlayer() {&amp;#xA;                var video = document.getElementById(&amp;#x27;video&amp;#x27;);&amp;#xA;                var player = new shaka.Player(video);&amp;#xA;                window.player = player;&amp;#xA;                player.addEventListener(&amp;#x27;error&amp;#x27;, onErrorEvent);&amp;#xA;                player.load(manifestUri).then(function() {&amp;#xA;                    console.log(&amp;#x27;The video has now been loaded!&amp;#x27;);&amp;#xA;                }).catch(onError);&amp;#xA;            }&amp;#xA;            function onErrorEvent(event) {&amp;#xA;                onError(event.detail);&amp;#xA;            }&amp;#xA;            function onError(error) {&amp;#xA;                console.error(&amp;#x27;Error code&amp;#x27;, error.code, &amp;#x27;object&amp;#x27;, error);&amp;#xA;            }&amp;#xA;            document.addEventListener(&amp;#x27;DOMContentLoaded&amp;#x27;, initApp);&amp;#xA;        &lt;/script&gt;&#xA;    &#xA;    &#xA;        &#xA;    &#xA;

  


  


  



  For some reason the stream is only playing the first chunk and never requesting for the next chunk. How can I make it load the next chunks ?

  


  When tried using dash.js I couldn't get it to load even the first chunk.

  


  Thanks in advance.

  


• how to choose a screen to capture with ffmpeg in qt on windows

  13 octobre 2020, par YouCL

  I am using qt with ffmpeg to record desktop on windows. My question is : if I have multiple screens, how to control the recording target ?

  


  Now I pass desktop to param url in function int avformat_open_input(AVFormatContext **ps, const char *url, AVInputFormat *fmt, AVDictionary **options); . Is there some other param form for url to control which screen to capture ?

  


  For example, if I only want to record the primary screen, what url value should I use ?

  


  I know qt can identify primary screen and other screens. Is there a way to pass the screen id to ffmpeg ?