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• Use deck.js as a remote presentation tool

  8 janvier 2014, par silvia

  deck.js is one of the new HTML5-based presentation tools. It’s simple to use, in particular for your basic, every-day presentation needs. You can also create more complex slides with animations etc. if you know your HTML and CSS.

  Yesterday at linux.conf.au (LCA), I gave a presentation using deck.js. But I didn’t give it from the lectern in the room in Perth where LCA is being held – instead I gave it from the comfort of my home office at the other end of the country.

  I used my laptop with in-built webcam and my Chrome browser to give this presentation. Beforehand, I had uploaded the presentation to a Web server and shared the link with the organiser of my speaker track, who was on site in Perth and had set up his laptop in the same fashion as myself. His screen was projecting the Chrome tab in which my slides were loaded and he had hooked up the audio output of his laptop to the room speaker system. His camera was pointed at the audience so I could see their reaction.

  I loaded a slide master URL :
  http://html5videoguide.net/presentations/lca_2014_webrtc/?master
  and the room loaded the URL without query string :
  http://html5videoguide.net/presentations/lca_2014_webrtc/.

  Then I gave my talk exactly as I would if I was in the same room. Yes, it felt exactly as though I was there, including nervousness and audience feedback.

  How did we do that ? WebRTC (Web Real-time Communication) to the rescue, of course !

  We used one of the modules of the rtc.io project called rtc-glue to add the video conferencing functionality and the slide navigation to deck.js. It was actually really really simple !

  Here are the few things we added to deck.js to make it work :

  • Code added to index.html to make the video connection work :

    <meta name="rtc-signalhost" content="http://rtc.io/switchboard/">
    
    <meta name="rtc-room" content="lca2014">
    
    ...
    
    <video id="localV" rtc-capture="camera" muted></video>
    
    <video id="peerV" rtc-peer rtc-stream="localV"></video>
    
    ...
    
    <script src="glue.js"></script>
    
    <script>
    
    glue.config.iceServers = [{ url: 'stun:stun.l.google.com:19302' }];
    
    </script>

    The iceServers config is required to punch through firewalls – you may also need a TURN server. Note that you need a signalling server – in our case we used http://rtc.io/switchboard/, which runs the code from rtc-switchboard.

  • Added glue.js library to deck.js :

    Downloaded from https://raw.github.com/rtc-io/rtc-glue/master/dist/glue.js into the source directory of deck.js.

  • Code added to index.html to synchronize slide navigation :

    glue.events.once('connected', function(signaller) {
    
      if (location.search.slice(1) !== '') {
    
        $(document).bind('deck.change', function(evt, from, to) {
    
          signaller.send('/slide', {
    
            idx: to,
    
            sender: signaller.id
    
          });
    
        });
    
      }
    
      signaller.on('slide', function(data) {
    
        console.log('received notification to change to slide: ', data.idx);
    
        $.deck('go', data.idx);
    
      });
    
    });

    This simply registers a callback on the slide master end to send a slide position message to the room end, and a callback on the room end that initiates the slide navigation.

  And that’s it !

  You can find my slide deck on GitHub.

  Feel free to write your own slides in this manner – I would love to have more users of this approach. It should also be fairly simple to extend this to share pointer positions, so you can actually use the mouse pointer to point to things on your slides remotely. Would love to hear your experiences !

  Note that the slides are actually a talk about the rtc.io project, so if you want to find out more about these modules and what other things you can do, read the slide deck or watch the talk when it has been published by LCA.

  Many thanks to Damon Oehlman for his help in getting this working.

  BTW : somebody should really fix that print style sheet for deck.js – I’m only ever getting the one slide that is currently showing.

• How to record desktop while on x2go session via a command line tool ?

  4 décembre 2017, par haragei

  the Goal :
  I am trying to record a specific X display on a remote server with a command line tool.

  the Problem :
  The output file contains a pure black video stream for the whole duration of the recording.

  My Approach :
  I am connecting to a remote server via x2go. The Server runs Ubuntu 16.04.2 with Xfce Desktop Environment. The Display I try to record is :50 (which gets created when I connect to the x2go server). I can control the remote server totally fine through x2go.

  My commands for recording via ffmpeg (or avconv/recordmydesktop, which use ffmpeg underneath) all look more or less the same and are like this :
  ffmpeg -f x11grab -r 25 -s 1854x1176 -i :50.0 -c:v libx264 screencast.mkv

  Sample output :

  user@machine:~/$ ffmpeg -f x11grab -r 25 -s 1854x1176 -i :50.0+0,0 -c:v libx264 -vb 4000k -an screencast.mkv
  
  ffmpeg version N-86766-g264f6c6 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  
    configuration: --prefix=/home/user/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/user/ffmpeg_build/include --extra-ldflags=-L/home/user/ffmpeg_build/lib --bindir=/home/user/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree
  
    libavutil      55. 67.100 / 55. 67.100
  
    libavcodec     57.100.104 / 57.100.104
  
    libavformat    57. 75.100 / 57. 75.100
  
    libavdevice    57.  7.100 / 57.  7.100
  
    libavfilter     6. 95.100 /  6. 95.100
  
    libswscale      4.  7.101 /  4.  7.101
  
    libswresample   2.  8.100 /  2.  8.100
  
    libpostproc    54.  6.100 / 54.  6.100
  
  [x11grab @ 0x1fd9b40] XFixes not available, cannot draw the mouse.
  
  [x11grab @ 0x1fd9b40] Stream #0: not enough frames to estimate rate; consider increasing probesize
  
  Input #0, x11grab, from ':50.0+0,0':
  
    Duration: N/A, start: 1500041497.684675, bitrate: N/A
  
      Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1854x1176, 25 fps, 1000k tbr, 1000k tbn, 1000k tbc
  
  File 'screencast.mkv' already exists. Overwrite ? [y/N] y
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
  Press [q] to stop, [?] for help
  
  [libx264 @ 0x1fe3040] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
  
  [libx264 @ 0x1fe3040] profile High 4:4:4 Predictive, level 4.2, 4:4:4 8-bit
  
  [libx264 @ 0x1fe3040] 264 - core 148 r2643 5c65704 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=4000 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, matroska, to 'screencast.mkv':
  
    Metadata:
  
      encoder         : Lavf57.75.100
  
      Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv444p, 1854x1176, q=-1--1, 4000 kb/s, 25 fps, 1k tbn, 25 tbc
  
      Metadata:
  
        encoder         : Lavc57.100.104 libx264
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/4000000 buffer size: 0 vbv_delay: -1
  
  [swscaler @ 0x1fe94e0] Warning: data is not aligned! This can lead to a speedloss
  
  frame=  179 fps= 36 q=-1.0 Lsize=      16kB time=00:00:07.04 bitrate=  18.8kbits/s speed=1.43x    
  
  video:14kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 12.869934%
  
  [libx264 @ 0x1fe3040] frame I:1     Avg QP: 6.00  size:   518
  
  [libx264 @ 0x1fe3040] frame P:45    Avg QP: 0.44  size:    81
  
  [libx264 @ 0x1fe3040] frame B:133   Avg QP: 0.94  size:    73
  
  [libx264 @ 0x1fe3040] consecutive B-frames:  0.6%  1.1%  0.0% 98.3%
  
  [libx264 @ 0x1fe3040] mb I  I16..4:  0.0% 100.0%  0.0%
  
  [libx264 @ 0x1fe3040] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4:  0.0%  0.0%  0.0%  0.0%  0.0%    skip:100.0%
  
  [libx264 @ 0x1fe3040] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.0%  0.0%  0.0%  direct: 0.0%  skip:100.0%
  
  [libx264 @ 0x1fe3040] final ratefactor: -23.85
  
  [libx264 @ 0x1fe3040] 8x8 transform intra:100.0%
  
  [libx264 @ 0x1fe3040] coded y,u,v intra: 0.0% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
  
  [libx264 @ 0x1fe3040] i16 v,h,dc,p:  0%  0% 100%  0%
  
  [libx264 @ 0x1fe3040] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  0%  0% 100%  0%  0%  0%  0%  0%  0%
  
  [libx264 @ 0x1fe3040] Weighted P-Frames: Y:0.0% UV:0.0%
  
  [libx264 @ 0x1fe3040] kb/s:15.56

  Using : Ubuntu 16.04.2 LTS

  I have successfully accomplished to capture the display :50 with "simplescreenrecorder", but that tool has no command line interface. It uses ffmpeg also, so it somehow should be possible to caputure the display but I can´t get it to work properly.

• rtsp to rtmp using ffmpeg or any tool wrapper

  27 août 2017, par Chakri

  I have a requirement where I need to restream the RTSP stream from camera source to RTMP server. I know this may sound a repeated question but my exact scenario is I cannot do it manually over command line with ffmpeg command. I need a wrapper where I receive the rtsp and rtmp url from external source say through REST invocation. Then the code can trigger the ffmpeg restream.

  Basically flow is like this :

  1. Camera source application sends RTSP read event(could be basic HTTP(REST) request with RTSP url, metadata about camera info, serial no etc) to my streamer app

  Ex : /usr/bin/ffmpeg -i rtsp ://10.144.11.22:554/stream1 -f flv rtmp ://10.13.11.121:1935/stream1

  2. Streamer app computes the RTMP server url for corresponding camera and triggers a ffmpeg command to stream RTSP to RTMP

  3. Streamer app triggers above(2) in separate thread and keeps reading the logs for monitoring purpose. Also identifies the end of RTSP stream and sends an update(Example : RTSP END) event to UI

  Now at point(2) I need a suggestion. Here I need a stable wrapper/api which can help. I tried this through some Java wrappers but the process hangs or fails to read the output from ffmpeg. Also I need to handle streams from many cameras where spawning thread for each one could be exhaustive.

  So I am looking for some similar api/wrapper in C++ or Go Lang which might have more closer interaction in handling ffmpeg command.

  Please point if similar issue is addressed elsewhere