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• Preventing the python and ffmpeg heroku buildpacks from overwriting LD_LIBRARY_PATH

  3 mars 2014, par Simon

  I'm deployng a Django app to heroku, which requires ffmpeg. To accomplish this I am using heroku-buildpack-multi to install both heroku-buildpack-ffmpeg and heroku-buildpack-python, and all of that works fine. The problem is my that app also depends on django-pylibmc-sasl, python-memcached, pylibmc et al. which, as per usual, heroku senses and automatically installs libmemcached for me.

  Here's where something goes a little wrong. If I remove the custom buildpack everything runs fine (except for ffmpeg obviously). As soon as I add it in, however, while I can run ffmpeg, python fails on import pylibmc (or rather on import _pylibmc inside the module itself). After a amount of head-scratching I decided to have a look at the environment variables, here's what I got :

  With only the Python buildpack enabled :

  LD_LIBRARY_PATH=/app/.heroku/vendor/lib

  With both the Python and the ffmpeg buildpacks enabled :

  LD_LIBRARY_PATH=:vendor/ffmpeg/lib

  It looks like one or both of the buildpacks simply overwrites the other, or avoids setting the variable should it be already set. The ffmpeg buildpack seems to set LD_LIBRARY_PATH in a way that looks kosher to me, while the Python buildpack does a few things that I don't really understand the reason for.

  Solution

  Anyway, after manually overriding the library path using heroku config:set LD_LIBRARY_PATH=/app/.heroku/vendor/lib:vendor/ffmpeg/lib I am able to use both libmemcached and ffmpeg, but it doesn't feel too robust. What if something changes in one of the buildpacks path settings, or I add another buildpack - then I would have to manually edit the library path variable.

  Better solution ?

  So, while this is not really an urgent question at all, I simply would like to know :

  • Is there a better way of solving this issue ?
  • Might I have made some configuration error leading up to the path conflict ?
  • Should this be considered a bug in either of the buildpacks ?

• How to quit pexpect launched ffmpeg with key q pressed

  25 février 2014, par Shuman

  i used pexpect to call ffmpeg which is a lengthy process. it took half an hour, how can i detect user has pressed q key to stop it ? just like when you press q when using ffmpeg command line tool

  the ffmpeg command line is
  ffmpeg -y -i url -c copy -absf aac_adtstoasc out.mp4

  the last line of ffmpeg output is

  ...
  
  Stream mapping:
  
    Stream #0:1 -> #0:0 (copy)
  
    Stream #0:2 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  frame=   84 fps= 77 q=-1.0 Lsize=  184626kB time=00:00:06.96 bitrate=217120.3kbits/s

  the code i have now is

  reo = re.compile("""\S+\s+(?P\d+)  # frame
  
                       \s\S+\s+(?P<fps>\d+)           # fps
  
                       \sq=(?P<q>\S+)                    # q
  
                       \s\S+\s+(?P<size>\S+)          # size
  
                       \stime=(?P<time>\S+)           # time
  
                       \sbitrate=(?P<bitrate>[\d\.]+) # bitrate
  
                       """, re.X)
  
  
  
  durationReo = (&#39;(?&lt;=Duration:\s)\S+(?=,)&#39;)
  
  
  
  cpl = thread.compile_pattern_list([
  
      pexpect.EOF,
  
      reo,
  
      durationReo
  
  ])
  
  
  
  while True:
  
      i = thread.expect_list(cpl, timeout=None)
  
      if i == 0: # EOF
  
          print "the sub process exited"
  
          break
  
      elif i == 1:
  
          frame_number = thread.match.group(0)
  
          print frame_number
  
          print reo.search(frame_number).groups()
  
          # thread.close
  
      elif i == 2:
  
          durationLine = thread.match.group(0)
  
          print &#39;Duration:&#39;, durationLine
  
          # print "something :",thread.match.group(1)
  
          pass
  
  </bitrate></time></size></q></fps>

  with this code i can already get the frame info and duration info, the ultimate goal is to create a textual progress bar with another python progressbar module. but with the ability to send the 'q' pressed signal to ffmpeg child process.

• How to playback RAW video and audio in VLC ?

  24 février 2014, par Lane

  I have 2 files...

  • RAW H264 video
  • RAW PCM audio (uncompressed from PCM Mu Law)

  ...and I am looking to be able to play them in a Java application (using VLCJ possibly). I am able to run the ffmpeg command...

  • ffmpeg -i video -i audio -preset ultrafast movie.mp4

  ...to generate a mp4, but it takes 1/8 of the source length (it takes 1 min to generate a movie for 8 min of RAW data). My problem is that this is not fast enough for me, so I am trying to playback with the RAW sources. I can playback the video with the VLC command...

  • vlc video —demux=h264 (if I don't specify this flag, it doesn't work)

  ...and it plays correctly, but gives me the error...

  [0x10028bbe0] main interface error : no suitable interface module
  [0x10021d4a0] main libvlc : Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
  [0x10aa14950] h264 demux error : this doesn't look like a H264 ES stream, continuing anyway
  [0x1003ccb50] main input error : Invalid PCR value in ES_OUT_SET_(GROUP_)PCR !
  shader program 1 : WARNING : Output of vertex shader 'TexCoord1' not read by fragment shader
  WARNING : Output of vertex shader 'TexCoord2' not read by fragment shader

  ...similarly, I can play the RAW audio with the VLC command...

  • vlc audio (note that I do not need to specify the —demux flag)

  ...so, what I am looking for is...

  1. How to playback the RAW audio and video together using the VLC CLI ?
  2. Recommendations for a Java Application solution ?

  ...thanks !