Sur d’autres sites (13277)

• GNU Radio + leandvb demodulation of DVB-S signals

  25 juillet 2016, par ShatteredPheonix

  I am new to signal processing and RF, however I am trying to receive Ham TV signals from the ISS in gnu radio and then demodulate them using leandvb so that I can playback the video through a standard player like VLC.

  So please excuse my incorrect terminology where used :

  I have the following GNU Radio Setup :
  

  A few things about the file I am using is that it was recorded at 1msps with a symbol rate of 1 which was done via USRP.

  After playing the flow graph this seem to be the result :
  

  The above image, to me looks like a fairly clean signal - in addition to this I can’t seem to clear it up anymore.

  However, when I put it through a DVB-S demodulater called leandvb it can’t seem to get any TS packets out.

  instead it reports :

  rawiq            : 1647M/549M   2048 writable  ,   2048 unread ( 0 
  
  2048 2048 )
  
  autonotched      : 2197M/549M   3072 writable !,   1024 unread ( 0 0 1024 0 )
  
  PSK symbols      : 955M/477M   4057 writable  ,   4870 unread ( 373 4870 )
  
  freq             :   0M/  0M      2 writable  ,      0 unread ( 0 )
  
  bytes            :   0M/  0M   9792 writable  ,      0 unread ( 0 )
  
  RS-enc packets   :   0M/  0M      4 writable  ,      0 unread ( 0 )
  
  rand TS packets  :   0M/  0M      4 writable  ,      0 unread ( 0 )
  
  TS packets       :   0M/  0M      4 writable  ,      0 unread ( 0 0 )
  
  SS               :   0M/  0M      1 writable  ,      1 unread ( 1 )
  
  packet counter   :   0M/  0M    400 writable  ,      0 unread ( 0 )
  
  Total buffer memory: 422 KiB

  it seems to have problems reading some symbols and raw data but I don’t know why and I have tried almost everything I can think of to get it work.

  and when I try to play the resulting ts file through mplayer / ffmpeg / ffplay / vlc I get various errors :

  • File does not contain Stream
  • Invalid data while preprocessing
  • Cannot prefill buffer

  Can anyone help me and tell me where I am going wrong ? As I am completely clueless and have been trying to solve this problem for about 2 weeks now ?

• Why the fps of concatenate video file change with old video file ?

  23 juin 2016, par Zuiche

  I have two wmv video file which 25fps.
  I concatenate these video file using ffmpeg command line like this :

  ffmpeg -r 25 -f concat -i 1.txt -c copy output.wmv

  1.txt :

  file 'g:\1.wmv'
  
  file 'g:\2.wmv' 

  It works. But the fps of output.wmv is 30.
  How can I maintain the fps of concatenate video file ?

  UPDATE
  ======Console Output========

  ffmpeg version N-73266-g4aa0de6 Copyright (c) 2000-2015 the FFmpeg developers
  
  built with gcc 4.9.2 (GCC)
  
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
  
  libavutil      54. 27.100 / 54. 27.100
  
  libavcodec     56. 45.101 / 56. 45.101
  
  libavformat    56. 40.100 / 56. 40.100
  
  libavdevice    56.  4.100 / 56.  4.100
  
  libavfilter     5. 19.100 /  5. 19.100
  
  libswscale      3.  1.101 /  3.  1.101
  
  libswresample   1.  2.100 /  1.  2.100
  
  libpostproc    53.  3.100 / 53.  3.100
  
  [wmv3 @ 04d452a0] Extra data: 8 bits left, value: 20
  
  [wmv3 @ 04d14d00] Extra data: 8 bits left, value: 20
  
  Input #0, concat, from '1.txt':
  
  Duration: N/A, start: 0.000000, bitrate: 4214 kb/s
  
  Stream #0:0: Video: wmv3 (Main) (WMV3 / 0x33564D57), yuv420p, 720x576, 4194 kb/s, SAR 16:15 DAR 4:3, 25 fps, 25 tbr, 1k tbn, 1k tbc
  
  Stream #0:1: Audio: wmavoice ([10][0][0][0] / 0x000A), 22050 Hz, mono, flt, 20 kb/s
  
  [asf @ 04d12120] Codec for stream 0 does not use global headers but container format requires global headers
  
  [asf @ 04d12120] Codec for stream 1 does not use global headers but container format requires global headers
  
  Output #0, asf, to 'output.wmv':
  
  Metadata:
  
  WM/EncodingSettings: Lavf56.40.100
  
  Stream #0:0: Video: wmv3 (WMV3 / 0x33564D57), yuv420p, 720x576 [SAR 16:15 DAR 4:3], q=2-31, 4194 kb/s, 25 fps, 25 tbr, 1k tbn, 25 tbc
  
  Stream #0:1: Audio: wmavoice ([10][0][0][0] / 0x000A), 22050 Hz, mono, 20 kb/s
  
  Stream mapping:
  
  Stream #0:0 -> #0:0 (copy)
  
  Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  [wmv3 @ 04ce8880] Extra data: 8 bits left, value: 20
  
  frame=  538 fps=0.0 q=-1.0 Lsize=    5723kB time=00:00:21.52 bitrate=2178.5kbits/s  
  
  video:5593kB audio:62kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.206905%

  =========FFprobe Output=========

  ffprobe version N-60456-g4040b56-Sherpya Copyright (c) 2007-2014 the FFmpeg developers
  
  built on Feb  9 2014 06:50:33 with gcc 4.8 (GCC)
  
  [wmv3 @ 050684e0] Extra data: 8 bits left, value: 20
  
  Input #0, asf, from 'output.wmv':
  
  Metadata:
  
  encoder         : Lavf56.40.100
  
  Duration: 00:00:21.52, start: 0.000000, bitrate: 2178 kb/s
  
  Stream #0:0: Video: wmv3 (Main) (WMV3 / 0x33564D57), yuv420p, 720x576, SAR 16:15 DAR 4:3, 25 tbr, 1k tbn, 1k tbc
  
  Stream #0:1: Audio: wmavoice ([10][0][0][0] / 0x000A), 22050 Hz, mono, flt, 20 kb/s
  
  [wmv3 @ 050684e0] Extra data: 8 bits left, value: 20

• Creating a VOD ABR system with HLS

  19 juillet 2016, par Matteo

  I know this is a specific question but I’m new to this and have spent weeks trying to solve this problem.

  I’m creating a mobile app and need to have Video on Demand (VOD) live streaming. Right now I’m converting MP4 video files into HLS using FFMPEG and broadcasting from a server but the load time is pretty long for 3G connections (low bandwith).

  Has anyone else set up this type of system that can help ?

  It looks like I need Adaptive Bitrate Streaming (ABR) and a media server with a CDN.

  My question is - #1 - Can I get away with not using a CDN ? Or perhaps not using a "media server" but just a regular server

  2 - Is it practical to use FFPMEG to set up an ABR stream with HLS

  I know I probably wont get a response to this question but I thought it was worth a shot.

  Thanks