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• How to detect audio sampling rate with avprobe / ffprobe ?

  8 août 2013, par Devy

  I am using libav 9.6, installed via Homebrew.

  $ avprobe -version
  
  avprobe version 9.6, Copyright (c) 2007-2013 the Libav developers
  
    built on Jun  8 2013 02:44:19 with Apple LLVM version 4.2 (clang-425.0.24) (based on LLVM 3.2svn)
  
  avprobe 9.6
  
  libavutil     52.  3. 0 / 52.  3. 0
  
  libavcodec    54. 35. 0 / 54. 35. 0
  
  libavformat   54. 20. 3 / 54. 20. 3
  
  libavdevice   53.  2. 0 / 53.  2. 0
  
  libavfilter    3.  3. 0 /  3.  3. 0
  
  libavresample  1.  0. 1 /  1.  0. 1
  
  libswscale     2.  1. 1 /  2.  1. 1

  Even though the sampling rate is displayed in the stdout in the command line output, the -show_format option doesn't surface the sampling rate information for the audio file at all.

  Here is the BASH terminal output :

  $ avprobe  -v verbose -show_format -of json  sample.gsm
  
  avprobe version 9.6, Copyright (c) 2007-2013 the Libav developers
  
    built on Jun  8 2013 02:44:19 with Apple LLVM version 4.2 (clang-425.0.24)
  
  (based on LLVM 3.2svn)
  
    configuration: --prefix=/usr/local/Cellar/libav/9.6 --enable-shared
  
  --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree
  
  --enable-hardcoded-tables --enable-avresample --enable-vda --enable-gnutls
  
  --enable-runtime-cpudetect --disable-indev=jack --cc=cc --host-cflags=
  
  --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame
  
  --enable-libxvid --enable-avplay
  
    libavutil     52.  3. 0 / 52.  3. 0
  
    libavcodec    54. 35. 0 / 54. 35. 0
  
    libavformat   54. 20. 3 / 54. 20. 3
  
    libavdevice   53.  2. 0 / 53.  2. 0
  
    libavfilter    3.  3. 0 /  3.  3. 0
  
    libavresample  1.  0. 1 /  1.  0. 1
  
    libswscale     2.  1. 1 /  2.  1. 1
  
  [gsm @ 0x7f8012806600] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, gsm, from 'sample.gsm':
  
    Duration: 00:03:52.32, start: 0.000000, bitrate: 13 kb/s
  
      Stream #0.0: Audio: gsm, 8000 Hz, mono, s16, 13 kb/s
  
  {  "format" : {
  
      "filename" : "sample.gsm",
  
      "nb_streams" : 1,
  
      "format_name" : "gsm",
  
      "format_long_name" : "raw GSM",
  
      "start_time" : "0.000000",
  
      "duration" : "232.320000",
  
      "size" : "383328.000000",
  
      "bit_rate" : "13200.000000"
  
    }}

  And the python code example :

  >>> filename = 'sample.gsm'
  
  >>> result = subprocess.check_output(['avprobe', '-show_format', '-of',
  
  'json', filename])
  
  avprobe version 9.6, Copyright (c) 2007-2013 the Libav developers
  
    built on Jun  8 2013 02:44:19 with Apple LLVM version 4.2
  
  (clang-425.0.24) (based on LLVM 3.2svn)
  
  [gsm @ 0x7fe0b1806600] Estimating duration from bitrate, this may be
  
  inaccurate
  
  Input #0, gsm, from 'sample.gsm':
  
    Duration: 00:03:52.32, start: 0.000000, bitrate: 13 kb/s
  
      Stream #0.0: Audio: gsm, 8000 Hz, mono, s16, 13 kb/s
  
  >>> print result
  
  {  "format" : {
  
      "filename" : "sample.gsm",
  
      "nb_streams" : 1,
  
      "format_name" : "gsm",
  
      "format_long_name" : "raw GSM",
  
      "start_time" : "0.000000",
  
      "duration" : "232.320000",
  
      "size" : "383328.000000",
  
      "bit_rate" : "13200.000000"
  
  }}

  So I am aware that sampling rate could be a stream specific display to be shown in -show_format option results. But there isn't any other options to detect the sampling rate on a specific audio stream even though it's possible to set it with -ar when re-encoding it.

  I filed a ticket to libav but I am just curious if there is any other way to extract sampling rate from libav probing utils. I appreciate the answer beforehand.

  PS : it would be the same question for the upstream project of ffmpeg (ffprobe) in this case.

• Recording audio with FFMPEG works in terminal but not through exec() of PHP

  8 août 2013, par lucasalmeida92

  I use this command to RECORD audio and video from my webcam in terminal and it works !

  ffmpeg -f video4linux2 -r 25 -sameq -s 640x480 -i /dev/video0 -f alsa -i plughw:0,0 -ar 22050 -ab 128k -y webcam.flv

  But when I do it through PHP, like this :

  echo shell_exec('ffmpeg -f video4linux2 -r 25 -sameq -s 640x480 -i /dev/video0 -f alsa -i plughw:0,0 -ar 22050 -ab 128k -y webcam.flv 2>&1 &') ;

  I receive that log :

  ffmpeg version 0.8.6-4:0.8.6-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers built on Apr 2 2013 17:02:36 with gcc 4.6.3 * THIS PROGRAM IS DEPRECATED * This program is only provided for compatibility and will be removed in a future release. Please use avconv instead. [video4linux2 @ 0x23579a0] Estimating duration from bitrate, this may be inaccurate Input #0, video4linux2, from '/dev/video0' : Duration : N/A, start : 4868.729067, bitrate : 122880 kb/s Stream #0.0 : Video : rawvideo, yuyv422, 640x480, 122880 kb/s, 25 tbr, 1000k tbn, 25 tbc Home directory /var/www not ours.

  ALSA lib pcm_hw.c:1401 :(_snd_pcm_hw_open) Invalid value for card [alsa @ 0x23589e0] cannot open audio device plughw:0,0 (No such file or directory) plughw:0,0 : Input/output error

  Before I got that Mic device problem I was having problem with the Webcam device's permissions, then i did :

      sudo chmod -R 777 /dev/video0

  And the video capture was ready to be used ! But now I got this Mic device problem !

  I think it can be about permissions too, but I dont know linux very well and have no idea how to fix that !

  Thanks !

  ---

  I just found the solution ! =x

  sudo chmod -R 666 /dev/snd/*

• webm to mp4 conversion using ffmpeg

  2 décembre 2015, par Pavan K

  When I try to convert a webm file to mp4 the output is very very choppy and it appears as if many frames have been dropped by ffmpeg

  I used the following commands to convert

  ffmpeg -i movie.webm movie.mp4
  
  ffmpeg -i movie.webm -vcodec libx264 movie.mp4
  
  ffmpeg -i movie.webm -vcodec libx264 -qscale 0 movie.mp4

  All of them have the same problem. When I use ffprobe it seems to show the frames more or less properly.

  UPDATE :

   built on Jun 14 2013 14:31:50 with gcc 4.7 (Ubuntu/Linaro 4.7.2-2ubuntu1)
  
    configuration: --prefix=/home/user2/ffmpeg_build --extra-cflags=-I/home/user2/ffmpeg_build/include --extra-ldflags=-L/home/pavan4/ffmpeg_build/lib --bindir=/home/pavan4/bin --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-x11grab
  
    libavutil      52. 35.101 / 52. 35.101
  
    libavcodec     55. 16.100 / 55. 16.100
  
    libavformat    55.  8.102 / 55.  8.102
  
    libavdevice    55.  2.100 / 55.  2.100
  
    libavfilter     3. 77.101 /  3. 77.101
  
    libswscale      2.  3.100 /  2.  3.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Hyper fast Audio and Video encoder
  
  usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...
  
  
  
  Use -h to get full help or, even better, run 'man ffmpeg'
  
  
  
  Input #0, matroska,webm, from '1.webm':
  
    Duration: 00:00:10.64, start: 0.000000, bitrate: 5024 kb/s
  
      Stream #0:0(eng): Video: vp8, yuv420p, 1280x720, SAR 1:1 DAR 16:9, 1k fps, 1k tbr, 1k tbn, 1k tbc (default)
  
  [libx264 @ 0x1d966a0] using SAR=1/1
  
  [libx264 @ 0x1d966a0] MB rate (3600000) > level limit (2073600)
  
  [libx264 @ 0x1d966a0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
  
  [libx264 @ 0x1d966a0] profile High, level 5.2
  
  [libx264 @ 0x1d966a0] 264 - core 133 r2 a3ac64b - H.264/MPEG-4 AVC codec - Copyleft 2003-2013 - 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=-2 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=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, mp4, to '1_conv4.mp4':
  
    Metadata:
  
      encoder         : Lavf55.8.102
  
      Stream #0:0(eng): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 16k tbn, 1k tbc (default)
  
  Stream mapping:
  
  Stream #0:0 -> #0:0 (vp8 -> libx264)
  
  Press [q] to stop, [?] for help
  
  frame=  168 fps=0.0 q=33.0 size=      62kB time=00:00:00.11 bitrate=4606.0kbits/frame=  293 fps=230 q=33.0 size=     138kB time=00:00:00.23 bitrate=4809.7kbits/
  
  
  
  video:5620kB audio:0kB subtitle:0 global headers:0kB muxing overhead 2.212461%
  
  [libx264 @ 0x1d966a0] frame I:46    Avg QP:18.50  size: 39849
  
  [libx264 @ 0x1d966a0] frame P:2940  Avg QP:18.27  size:  1222
  
  [libx264 @ 0x1d966a0] frame B:7651  Avg QP:17.68  size:    43
  
  [libx264 @ 0x1d966a0] consecutive B-frames:  4.0%  0.2%  0.3% 95.5%
  
  [libx264 @ 0x1d966a0] mb I  I16..4: 19.9% 63.2% 16.9%
  
  [libx264 @ 0x1d966a0] mb P  I16..4:  0.2%  0.5%  0.1%  P16..4:  3.9%  1.1%  0.6%  0.0%  0.0%    skip:93.6%
  
  [libx264 @ 0x1d966a0] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.2%  0.0%  0.0%  direct: 0.0%  skip:99.8%  L0:25.1% L1:74.9% BI: 0.0%
  
  [libx264 @ 0x1d966a0] 8x8 transform intra:63.6% inter:75.9%
  
  [libx264 @ 0x1d966a0] coded y,uvDC,uvAC intra: 61.5% 53.4% 24.4% inter: 0.5% 0.5% 0.0%
  
  [libx264 @ 0x1d966a0] i16 v,h,dc,p: 52% 19% 19% 11%
  
  [libx264 @ 0x1d966a0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 32% 17% 13%  4%  6%  9%  5%  8%  6%
  
  [libx264 @ 0x1d966a0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 18% 14%  5%  8% 10%  6%  6%  3%
  
  [libx264 @ 0x1d966a0] i8c dc,h,v,p: 55% 17% 24%  4%
  
  [libx264 @ 0x1d966a0] Weighted P-Frames: Y:0.0% UV:0.0%
  
  [libx264 @ 0x1d966a0] ref P L0: 82.5% 13.2%  4.0%  0.3%
  
  [libx264 @ 0x1d966a0] ref B L0: 60.2% 39.2%  0.6%
  
  [libx264 @ 0x1d966a0] ref B L1: 98.5%  1.5%
  
  [libx264 @ 0x1d966a0] kb/s:4327.77