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• Algorithm to draw waveform from audio

  27 février 2016, par yayuj

  I’m trying to draw a waveform from a raw audio file. I demuxed/decoded an audio file using FFmpeg and I have those informations : samples buffer, the size of the samples buffer, the duration of the audio file (in seconds), sample rate (44100, 48000, etc), sample size, sample format (uint8, int16, int32, float, double), and the raw audio data itself.

  Digging on the Internet I found this algorithm (more here) :

  White Noise :

  

  The Algorithm

  All you need to do is randomize every sample from –amplitude to
  amplitude. We don’t care about the number of channels in most cases so
  we just fill every sample with a new random number.

  Random rnd = new Random();
  
  short randomValue = 0;
  
  
  
  for (int i = 0; i < numSamples; i++)
  
  {
  
      randomValue = Convert.ToInt16(rnd.Next(-amplitude, amplitude));
  
      data.shortArray[i] = randomValue;
  
  }

  It’s really good but I don’t want to draw that way, but this way :

  

  Is there any algorithm or idea of how I can be drawing using the informations that I have ?

• ffmpeg output + issues

  3 octobre 2014, par Ford

  I am trying to get ffmpeg to work using PHP, in its most basic format, just as a test before i develop my code further.

  However i can not get it to work and get no error messages or indications to what is wrong :-(

  i am trying :

  echo exec("/usr/bin/ffmpeg -y -i /home/xxxxxx/public_html/videos/1746/0765916.avi /home/xxxxxx/public_html/videos/1746/test.mp4"); 

  this is creating a 0kb file, but nothing else :-(
  i get no error message (or anything else !)

  (i have error_reporting turned ON and nothing is displayed in browser or server logs)

  if i add the below to get the codecs available :

  echo exec("ffmpeg -formats");

  this just outputs "worse."

  I do not have access to command line, as i am using a shared hosting server.

  I have had the host run the above from command line, and they say it says "codec not found" or words to the effect.

  is there any way i can get any error output into my php file so i can see what is happening.

  Also how do i go about installing codecs, if this is the problem (the host will install them, but have mentioned they have never installed a codec on a Linux box, so would be grateful if i could point them to any install info too)

  Thanks in advance !

  EDIT :

  after adding in the code that @stewe suggests, this is the output when trying to convert to mp4

  (i can convert to to other formats fine )

  FFmpeg version SVN-r0.5.10-4:0.5.10-1, Copyright (c) 2000-2009 Fabrice
  
  Bellard, et al. configuration: --extra-version=4:0.5.10-1
  
  --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libdirac --enable-libgsm --enable-libopenjpeg --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libfaad --enable-libdc1394 --enable-shared --disable-static libavutil 49.15. 0 / 49.15. 0 libavcodec 52.20. 1 / 52.20. 1 libavformat 52.31. 0 /
  
  52.31. 0 libavdevice 52. 1. 0 / 52. 1. 0 libavfilter 0. 4. 0 / 0. 4. 0 libswscale 0. 7. 1 / 0. 7. 1 libpostproc 51. 2. 0 / 51. 2. 0 built on
  
  Feb 16 2013 10:07:01, gcc: 4.4.5 Input #0, avi, from
  
  '/home/xxxxx/public_html/videos/1746/0765916.avi':
  
  Duration: 00:01:37.56, start: 0.000000, bitrate: 868 kb/s Stream #0.0:
  
  Video: mpeg4, yuv420p, 480x272 [PAR 1:1 DAR 30:17], 25 tbr, 25 tbn, 25
  
  tbc Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 128 kb/s Output
  
  #0, mp4, to '/home/xxxxx/public_html/videos/1746/test.mp4':
  
  Stream #0.0: Video: mpeg4, yuv420p, 480x272 [PAR 1:1 DAR 30:17],
  
  q=2-31, 200 kb/s, 90k tbn, 25 tbc Stream #0.1: Audio: 0x0000, 48000
  
  Hz, stereo, s16, 64 kb/s Stream mapping: Stream #0.0 -> #0.0 Stream
  
  #0.1 -> #0.1 [mpeg4 @ 0x9fb7880]removing common factors from framerate Unsupported codec for output stream #0.1

  If anyone can help as to how to fix this issue, as i would ideally like to convert to mp4

• libFLAC/cpu.c : Simplify OS SSE support detection.

  28 juillet 2014, par Erik de Castro Lopo

  libFLAC/cpu.c : Simplify OS SSE support detection.
  Simplify the code that tries to detect whether OS supports SSE instructions.
  a) Linux : "old" vs "new" sigaction
  OBSOLETE_SIGCONTEXT_FLAVOR was disabled in Mar 2007 in commit 1ca3a445f.
  
  According to <http://unixhelp.ed.ac.uk/CGI/man-cgi?sigaction>: "Support for
  
  SA_SIGINFO was added in Linux 2.2" (released in Jan 1999). If noone wants to
  
  use FLAC with Linux kernel 2.0 then it’s safe to delete this code.
  b) MSVC : try/catch vs. sigill_handler
  TRY_CATCH_FLAVOR was enabled in Jan 2009 in commit a832ef32. According to the
  
  comment in cpu.c, "sigill_handler flavor resulted in several crash reports on
  
  win32". Also this sigill_handler flavor is not thread-safe.
  c) MinGW : fxsave/fxrestore vs. sigill_handler
  The code was added Mar 2014 in commit 99d5154f. It’s better to use FXSR flavor
  
  instead of sigill_handler flavor. The reasons are the same as for MSVC.
  Patch-from : lvqcl <lvqcl.mail@gmail.com>
  

  • [DH] src/libFLAC/cpu.c