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• Anomalie #3576 : a travaillé sur cet article ...

  8 novembre 2015, par Ben .

  Quand on l’a vu c’était avec jluc (qui est rédacteur sur le blog) et nous on voyait qu’il avait modifié cet article http://blog.spip.net/ecrire/?exec=article&id_article=780 ( qui n’a pas d’embeded)

• Low latency video player on android

  20 mai 2021, par Louis Blenner

  I'd like to be able to stream the video from my webcam to an Android app with a latency below 500ms, on my local network.

  


  To capture and send the video over the network, I use ffmpeg.

  


  ffmpeg -f v4l2 -i /dev/video0 -preset ultrafast -tune zerolatency -vcodec libx264 -an -vf format=yuv420p -f mpegts  udp://192.168.1.155:5000


  


  This command takes the webcam as an input, convert it and send it to a device using the mpegts protocol.
  
This is not a requirement, if another technique could work, I could change the way I send the video.

  


  I am able to read the video on another PC from the local network with a latency below 500 ms, using commands like

  


  gst-launch-1.0 -v udpsrc port=5000 ! video/mpegts ! tsdemux ! h264parse ! avdec_h264 ! fpsdisplaysink sync=false


  


  or

  


  mpv udp://0.0.0.0:5000 --no-cache --untimed --no-demuxer-thread --video-sync=audio --vd-lavc-threads=1 


  


  So it is possible to have this range of latency.
  
I'd like to have the same thing on Android.

  


  Here are my tries to do that.

  


  Exoplayer

  


  After looking at the different players available on Android studio, it seems like Exoplayer is the go-to choice.
  
I tried different options indicated in the live-streaming documentation, but I always end up with a stream taking seconds to start and with a latency of seconds.
  
I tried to add a Button to seek to the default position of the windows, but it results in a loading of several seconds.

  


  DefaultExtractorsFactory extractorsFactory =
                new DefaultExtractorsFactory()
                        .setTsExtractorFlags(DefaultTsPayloadReaderFactory.FLAG_IGNORE_AAC_STREAM);

        player = new SimpleExoPlayer.Builder(this)
                .setMediaSourceFactory(
                        new DefaultMediaSourceFactory(this, extractorsFactory))
                .setLoadControl(new DefaultLoadControl.Builder()
                        .setBufferDurationsMs(DefaultLoadControl.DEFAULT_MIN_BUFFER_MS, DefaultLoadControl.DEFAULT_MAX_BUFFER_MS, 200, 200)
                        .build())
                .build();
        MyPlayerView playerView = findViewById(R.id.player_view);
        // Bind the player to the view.
        playerView.setPlayer(player);
        // Build the media item.
        MediaItem mediaItem = new MediaItem.Builder()
                .setUri(Uri.parse("udp://0.0.0.0:5000"))
                .setLiveMaxOffsetMs(500)
                .setLiveTargetOffsetMs(0)
                .setLiveMinOffsetMs(0)
                .build();
        // Set the media item to be played.
        player.setMediaItem(mediaItem);
        // Prepare the player.
        player.setPlayWhenReady(true);
        player.prepare();
        //player.seekToDefaultPosition();


  


  This issue is about the same issue and the conclusion was that Exoplayer was not fit for this use case.

  


  


  I'll be honest, ultra low-latency like this isn't ExoPlayer's main use-case

  


  


  Vlc

  


  Another try was to use the Vlc library.
  
But I was unable to have the same low latency stream as with the two previous players with Vlc.
  
I tried changing the preferences of Vlc to stream as fast as possible as described here

  


  Input/Codecs -> x264 preset: ultrafast - zerolatency
Input/Codecs -> Access Module: UDP input
Input/Codecs -> Clock Jitter: 500
Audio: disable audio


  


  I also tried reducing the different buffers.
  
However, I still have a latency of more than 1 seconds with that.

  


  Gstreamer

  


  Another try was to create a react-native project to use the different players available here.
  
One player that seemed promising was react-native-gstreamer because it uses gstreamer which is able to stream with low latency (gst-launch command).
  
But the library is now outdated.

  


  Question

  


  There were other tries, but none were successful.
  
Is there a problem with one of my approaches ?
  
And if not, Is there a player on Android (that I missed) which is able to achieve low latency stream like gstream or mpv on linux ?

  


• Playing With File

  8 septembre 2011, par Multimedia Mike — General

  I played with the ‘file’ utility a long time ago because I wanted to make it recognize a large number of multimedia formats. I had trouble getting my changes to take. But I’m prepared to try again after many years.

  Aiming at the Corpus
  In my local mirror of the MPlayerHQ samples archive, I find 9853 unique files. So I run all of them through the ‘file’ command :

    ’find /path/to/samples -type f -print0 | xargs -0 file —no-pad’
  

  My Ubuntu installation has file v5.04. I also tested against 5.07 and the latest, 5.08. Here is the number of files each version was unable to identify (generically marking as ‘data’) :

  5.04  1521
  5.07  1405
  5.08  1501
  

  That seems like a regression for v5.08 until I dug into the details and saw quite a few items like this, indicating that the MPEG detection could use some work :

  
   mov/mov-demux-infinite-loop.mpg : DOS-executable (
  +mov/mg-‹demux-infinite-loop.mpg : data
  
   image-samples/UNeedQT4.pntg : DOS-executable (
  +imY- samples/UNeedQT4.pntg : data
  

  Workflow
  These are just notes to myself and perhaps anyone else who wants to add new file formats to be identified by the ‘file’ command.

  First, download either the latest release from the FTP or clone from Github. Do the usual unpack, ‘./configure’, ‘make’ routine. To use this newly-built version and its associated magic file :

    ./src/file —magic-file magic/magic.mgc <file>
  

  To add a new format for ID, first, run the foregoing command to ensure that it’s not already identified. Then, check over the files in magic/Magdir and see which one might pertain to what you’re doing (it’s unlikely that your format will merit a new file in this directory). For example, for this round, I modified animation, audio, iff, and riff. Add or modify existing specs based on the copious examples in the directory and by consulting the appropriate man page (‘man 5 magic’).

  Finally, run ‘make’ again which will regenerate the magic file. Invoke the above command again to use the modified magic file.

  Before and After
  On a selection of formats taken from the samples archive (renamed and cut down to a kilobyte because detection typically only relies on the first few bytes), here is the “before” :

  amv :            RIFF (little-endian) data
  armovie :        data
  bbc-dirac :      data
  interplay-mve :  data
  mtv :            data
  nintendo-thp :   data
  nullsoft-video : data
  redcode :        data
  sega-film :      data
  smacker :        data
  trueaudio :      data
  vqa :            IFF data
  wavpack :        data
  wc3-mve :        IFF data
  wtv :            data
  

  And the “after” :

  amv :            RIFF (little-endian) data, AMV
  armovie :        ARMovie
  bbc-dirac :      BBC Dirac Video
  interplay-mve :  Interplay MVE Movie
  mtv :            MTV Multimedia File
  nintendo-thp :   Nintendo THP Multimedia
  nullsoft-video : Nullsoft Video
  redcode :        REDCode Video
  sega-film :      Sega FILM/CPK Multimedia, 320 x 224
  smacker :        RAD Game Tools Smacker Multimedia version 2, 320 x 200, 100 frames
  trueaudio :      True Audio Lossless Audio
  vqa :            IFF data, Westwood Studios VQA Multimedia, 418 video frames, 320 x 200
  wavpack :        WavPack Lossless Audio
  wc3-mve :        IFF data, Wing Commander III Video, PC version
  wtv :            Windows Television DVR Media
  

  After rerunning ‘file’ on the mphq corpus using the modified magic file, only 1329 files remain unidentified (down from 1501).

  Going Forward
  As mentioned, MPEG detection could probably be strengthened. However, a major weakness is QuickTime/MP4. Many files are not detected, probably owing to the many ways that QuickTime files can begin.