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• How to repair a raw H.264 stream using FFmpeg

  13 janvier 2020, par Chris Kennedy

  I apologize if I start rambling or seem incoherent.

  Preface : My house caught on fire last week.

  I have been trying to get the footage off my security camera system (Zmodo, don’t ever buy this crap) to share with the fire marshal and my insurance. I can’t get it off the "proper" way because the box doesn’t detect any drive or any file system I throw at it, and none of their viewing apps (for Android or Windows) allow video downloads.

  I was able to get the files directly from the system’s hard drive, but they’re (of course) messed up in such a way that I can’t just open up VLC (or even Zmodo’s own viewing software !) and view them. I have spent several hours scouring the web for various ways to run it through FFmpeg to see if it can repair the file, but I’ve had no luck so far and my mind is already stretched thin with everything else.

  This is the output from ffprobe :

  ffprobe version 4.2.1 Copyright (c) 2007-2019 the FFmpeg developers
  
    built with gcc 9.1.1 (GCC) 20190807
  
    configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  
    libavutil      56. 31.100 / 56. 31.100
  
    libavcodec     58. 54.100 / 58. 54.100
  
    libavformat    58. 29.100 / 58. 29.100
  
    libavdevice    58.  8.100 / 58.  8.100
  
    libavfilter     7. 57.100 /  7. 57.100
  
    libswscale      5.  5.100 /  5.  5.100
  
    libswresample   3.  5.100 /  3.  5.100
  
    libpostproc    55.  5.100 / 55.  5.100
  
  [h264 @ 000002479ee1c180] Format h264 detected only with low score of 1, misdetection possible!

  Then this repeats several dozen times :

      Last message repeated 1 times
  
  [h264 @ 000002479ee1de40] decode_slice_header error
  
  [h264 @ 000002479ee1de40] no frame!
  
  [h264 @ 000002479ee1de40] non-existing PPS 0 referenced

  And it finishes off with this :

  [h264 @ 000002479ee1c180] Could not find codec parameters for stream 0 (Video: h264, none): unspecified size
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, h264, from '.\recfile_-200102-130000-135959-00001100.264':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: h264, none, 25 fps, 25 tbr, 1200k tbn, 50 tbc

  I have tried several options with ffmpeg, including force_key_frames, setting the analyzeduration and probesize options to max_int, tried a -c copy, forcibly specified x264, tried to force a specific resolution (which it should all be standard HD video), and several others that I can’t recall at the moment.

  The video files are also accompanied by a .IDX file, but I haven’t figured out how important they are if they are at all to the video file.

  I can provide links to the smallest video and its associated IDX if needed, but if anyone can think of anything else to try on these files I’d greatly appreciate it.

• Anomalie #3920 (Nouveau) : sur Sauvegarde SQLite (SPIP 3.1.3 et 3.1.4 mini)

  11 mars 2017, par YannX DYX

  En SPIP 3 la sauvegarde standard pose parfois des problèmes, que j’ai trop souvent vus...
  Cette fois j’ai investigué sur un SPIP 3.1.4 OVH (avec prefix spécifique), toutes les tables ne sont pas sauvegardées, au contraire de la sauvegarde SQL : certes un message existe mais !
  - d’une part des tables vides ou non déclarées dans un plugin activé sont omises : pourquoi ?
  (encore une fois au contraire de la sauvegarde SQL encore disponible en plugin !)
  => est-il possible d’apporter un lien vers une aide plus détaillée, explicitant les causes possibles ?
  (cf. http://forum.spip.net/fr_262960.html & http://forum.spip.net/fr_266342.html par exemple).
  - le long libellé affiché <:dump:texte_sauvegarde:> ne signale aucunement ces aspects et indications ; le lien vers http://www.spip.net/fr_article1489.html est-il encore pertinent (je n’ai jamais tenté une restauration d’une autre version SQLite : comment se passerait une table non déclarée ou non connue dans le SPIP cible ? ) ?
  - d’autre part la lecture du message en fin des erreurs est peu explicite à la lecture (cf. ci-dessous),
  il me semblerait plus significatif d’afficher : Nombre de tables non sauvegardées : 12/58
  - d’ailleurs l’affichage est incorrect, car il n’indique pas le bon préfixe (en cas de préfixe non-standard !!)
  (et de ce fait, je vais avouer avoir jusqu’à présent négligé ces erreurs incomprises, et... patatras !)
  _ S’il est intéressant de faire une sauvegarde dé-préfixée (ce que j’ai parfois trouvé utile), peut-etre serait-il intéressant de faire apparaitre (dans un commentaire ou une meta) le préfixe d’origine, à titre de documentation !

  En recherchant de la documentation, je n’ai trouvé que http://www.spip.net/fr_article3418.html qui mériterait peut-etre d’etre complété avec les informations/explications ci-dessus (et leurs conséquences)...

  En complément, le site exemple ayant été migré d’anciennes versions SPIP 2, montre encore les anciennes tables@ spip_mots_xx@
  je ne me souviens pas d’un plugin qui éliminerait ces anciennes tables résiduelles (pour ceux qui ne savent utiliser phpMyAdmin ou Adminer)... ce qui supprimerait ensuite ces erreurs / voir par exemple sur les forums SPIP)

• Low latency video streaming on android

  17 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.

  


  I am able to read the video on another PC 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 example with Vlc.
  
I tried changing the preferences of Vlc to stream as fast as possible.

  


  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 ?