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• FFmpeg/Libav audio decode example

  19 mai 2015, par Walid Baccari

  I am trying to get the same output as that of ffmpeg/avconv from converting an MP2 file to raw PCM using code. I used the audio_decode_example function from the tutorial included in the FFmpeg/Libav documentation but the outputs were different.

  What steps does the ffmpeg/avconv command perform that I need to add to my program to get the same output ?

  Edit :
  This is the output from avconv -v debug -i test.mp2 test.sw :

  avconv version v10_beta1-302-g606cc8a, Copyright (c) 2000-2014 the Libav developers
  
  built on Mar 20 2014 20:28:32 with gcc 4.8 (Ubuntu/Linaro 4.8.1-10ubuntu9)
  
  configuration: 
  
  libavutil     53.  6. 0 / 53.  6. 0
  
  libavcodec    55. 34. 1 / 55. 34. 1
  
  libavformat   55. 12. 0 / 55. 12. 0
  
  libavdevice   54.  0. 0 / 54.  0. 0
  
  libavfilter    4.  3. 0 /  4.  3. 0
  
  libavresample  1.  2. 0 /  1.  2. 0
  
  libswscale     2.  1. 2 /  2.  1. 2
  
  Splitting the commandline.
  
  Reading option '-v' ... matched as option 'v' (set libav* logging level) with argument 'debug'.
  
  Reading option '-i' ... matched as input file with argument 'test.mp2'.
  
  Reading option 'test1.sw' ... matched as output file.                                  
  
  Finished splitting the commandline.                                       
  
  Parsing a group of options: global .                
  
  Applying option v (set libav* logging level) with argument debug.
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input file test.mp2.
  
  Successfully parsed a group of options.
  
  Opening an input file: test.mp2.
  
  [mp3 @ 0x27e5060] Probed with size=2048 and score=51
  
  [mp3 @ 0x27e5060] Estimating duration from bitrate, this may be inaccurate
  
  Guessed Channel Layout for  Input Stream #0.0 : stereo
  
  Input #0, mp3, from 'test.mp2':
  
    Duration: 00:00:04.80, start: 0.000000, bitrate: 64 kb/s
  
      Stream #0.0, 200, 1/14112000: Audio: mp2, 48000 Hz, stereo, s16p, 64 kb/s
  
  Successfully opened the file.
  
  Parsing a group of options: output file test1.sw.
  
  Successfully parsed a group of options.
  
  Opening an output file: test1.sw.
  
  Successfully opened the file.
  
  Detected 2 logical cores.
  
  [abuffer @ 0x27e5860] tb:1/48000 samplefmt:s16p samplerate: 48000 ch layout:0x3
  
  [abuffersink @ 0x2807040] auto-inserting filter 'auto-inserted fifo 0' between the filter 'audio format for output stream 0:0' and the filter 'output stream 0:0'
  
  [aformat @ 0x2806bc0] auto-inserting filter 'auto-inserted resampler 0' between the filter 'Parsed filter 0 anull' and the filter 'audio format for output stream 0:0'
  
  [AVAudioResampleContext @ 0x28092a0] audio_convert: found function: s16p to s16  (C)
  
  [AVAudioResampleContext @ 0x28092a0] audio_convert: found function: s16p to s16  (SSE2)
  
  [resample @ 0x2808560] fmt:s16p srate:48000 cl:stereo -> fmt:s16 srate:48000 cl:stereo
  
  Output #0, s16le, to 'test1.sw':
  
    Metadata:
  
      encoder         : Lavf55.12.0
  
      Stream #0.0, 0, 1/90000: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
  
    Stream mapping:
  
      Stream #0:0 -> #0:0 (mp2 -> pcm_s16le)
  
  Press ctrl-c to stop encoding
  
  Input stream #0:0 frame changed from rate:48000 fmt:s16p ch:2 chl:stereo to rate:48000 fmt:s16 ch:2 chl:stereo
  
  Detected 2 logical cores.
  
  [abuffer @ 0x2806e40] tb:1/48000 samplefmt:s16 samplerate: 48000 ch layout:0x3
  
  [abuffersink @ 0x2806fa0] auto-inserting filter 'auto-inserted fifo 0' between the filter 'audio format for output stream 0:0' and the filter 'output stream 0:0'
  
  No more output streams to write to, finishing.
  
  size=     900kB time=4.80 bitrate=1536.0kbits/s    
  
  video:0kB audio:0kB global headers:0kB muxing overhead 0.000000%

• unable to list capturing devices in ubuntu untill cheese is started

  25 mai 2015, par 89n3ur0n

  I have already created the question here at askubuntu but no one seems to be responding. So thought this active group can help me out. Here is the link to the problem :
  Problem is capture device is not found until I start cheese on my ubuntu 14.04.

  http://askubuntu.com/questions/627942/audio-device-not-found-arecord-l-has-strange-behaviour

  Please help me out.
  Cheers !

• FFMPEG GOP Extraction

  29 mars 2015, par user3601375

  I have an MPEG -4 video and I would like to extract a one GOP (Group of pictures ) at a time to BMPs (using FFMPEG and c++ (code block) ) rather than the whole video in one go, since now all my code writing is stuck there I use to sketch everything in my mind then program and I can’t imagine how to do this, I searched the net for something like that but of no use.. any command line or any library used to do that (I have no full experience on FFMPEG I have read the documentation but that thing was not there). I will appreciate any kind help and thanks for reading y post.

  Regards,