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• Huge latency in HTTP streaming desktop to browser

  29 janvier 2019, par fineman

  I’m trying to put together a reliable, reasonably low (<2s) latency desktop window share to browser solution. Currently I have :

  client sender using FFMPEG :

  ffmpeg -f gdigrab -i "title=notepad.exe" -r 10 -framerate 10  -c:v libx264 -g 50  -preset fast -tune zerolatency -f rtp rtp://192.168.1.85:1234

  server re-stream to HTTP using VLC :

  vlc -vv test.sdp  --sout=#transcode{vcodec=theo,vb=1600,scale=1,channels=1,acodec=none}:http{dst=:8080/webcam.ogg} :no-sout-rtp-sap :no-sout-standard-sap :sout-keep 

  where the sdp file is generated from the output of the ffmpeg command

  Client browser :

  <video autoplay="autoplay" loop="loop" muted="muted" preload="auto">
  
  <source src="http://192.168.1.85:8080/webcam.ogg" type="video/ogg"></source>
  
  </video>

  This works and gives good quality. But the latency is terrible (around 10s) and I’m at a loss to know how to tune it. I know that the latency is in the VLC transcoding/restreaming - displaying the RTP stream from the client on the server only has around 1s lag.

  I guess there are two questions - can this approach be sensibly tuned, or is the approach wrong to start with ?

• FFMPEG Dash with tiles of thumbnail images

  31 juillet 2020, par martyn Gilbert

  As of DASH-IF IOP version 4.2, section 6.2.6 defines the notion of image-based tracks in DASH :&#xA;https://dashif.org/docs/DASH-IF-IOP-v4.3.pdf.

  &#xA;&#xA;

  This is the ability to have an adaption set made up of mime type images that themselves are a strip of low resolution thumbnails. &#xA;A player will use these thumbnails when the user hovers their mouse over the video timeline and get a &#xA;preview of the the frame at that approximate timecode.

  &#xA;&#xA;

  Theo player website has a page dedicated to this function for playback :&#xA;https://www.theoplayer.com/blog/in-stream-thumbnail-support-dvr-dash-streams

  &#xA;&#xA;

  I need to generate a dash stream (not live) using ffmpeg that also contains these thumbnails. &#xA;I already have an ffmpeg command that will generate the film strip of jpgs which outputs a thumbnail every 5 seconds of input video and joins 5 of these together in a single jpg :

  &#xA;&#xA;

  ffmpeg -i INPUT -q:v 20 -vf "select=not(mod(n\,125)),scale=480:270,tile=5x1" -vsync vfr output%d.jpg

  &#xA;&#xA;

  and the mpeg dash itself :

  &#xA;&#xA;

  ffmpeg -i INPUT -y -map 0 -acodec aac -ac 2 -ar 48000 -s 960x540 -vcodec libx264 -f dash -preset veryfast -b:v:2 1500k -seg_duration 2 output.mpd

  &#xA;&#xA;

  But I cannot find a way in ffmpeg to include the thumbnails in the dash mpd file.

  &#xA;

• add libaribb24 ARIB STD-B24 caption decoder

  14 janvier 2019, par Jan Ekström

  add libaribb24 ARIB STD-B24 caption decoder
  * Outputs ASS lines with basic coloring and font scaling for each
  
    given region.
  
  * Sets the default style to the resolution of the subtitle plane
  
    (for example, 960x540 / 36pt font for profile A).
  
  * Has options to :
  
    * Disable ruby text (which is coded as regions which have
  
      half-height text in libaribb24).
  
      Enabled by default as without positioning ruby text only
  
      confuses as it is usually coded in the beginning of the decoded
  
      subtitle line.
  
    * Set the working directory, in which libaribb24 will read
  
      configuration as well as into which it may save broadcast extra
  
      symbols as PNG.
  
      Unset by default.
  The unconventional library check can be explained by the library's
  
  current master branch being licensed as LGPLv3, but at the time of
  
  writing the latest official release is still licensed under GPLv3.
  Thus, one either has to wait for the following release, or enable
  
  GPLv3.
  

  • [DH] Changelog
  • [DH] configure
  • [DH] doc/decoders.texi
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/allcodecs.c
  • [DH] libavcodec/avcodec.h
  • [DH] libavcodec/codec_desc.c
  • [DH] libavcodec/libaribb24.c
  • [DH] libavcodec/profiles.c
  • [DH] libavcodec/profiles.h
  • [DH] libavcodec/version.h