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• ffmpeg does not make a video from my images

  21 octobre 2014, par QuantumFool

  I’ve currently got some images that I’d like to display in the form of a movie. So, I pocked around a bit and found ffmpeg. This is the tutorial I have been going with :

  http://zulko.github.io/blog/2013/09/27/read-and-write-video-frames-in-python-using-ffmpeg/

  Since I don’t care about reading, I skipped right to the writing section. As far as I can tell, this is what my program should say :

  import subprocess as sp
  
  FFMPEG_BIN = "ffmpeg" #I'm on Ubuntu
  
  command = [ FFMPEG_BIN,
  
              '-y',
  
              '-f', 'rawvideo',
  
              '-vcodec', 'rawvideo',
  
              '-s', '1000x1000',
  
              '-pix_fmt', 'rgb24',
  
              '-r', '24',
  
              '-i', '-',
  
              '-an',
  
              '-vcodec', 'mpeg',
  
              'my_output_videofile.mp4' ]
  
  
  
  
  
  pipe = sp.Popen( command, stdin = sp.PIPE, stderr = sp.PIPE)

  However, when I run this in spyder, I get the error message :

  Traceback (most recent call last):
  
    File "<stdin>", line 1, in <module>
  
    File "/usr/lib/python2.7/dist-packages/spyderlib/widgets/externalshell/sitecustomize.py", line 540, in runfile
  
      execfile(filename, namespace)
  
    File "/home/xander/Downloads/python-meep/makeVideo.py", line 15, in <module>
  
      pipe = sp.Popen( command, stdin = sp.PIPE, stderr = sp.PIPE )
  
    File "/usr/lib/python2.7/subprocess.py", line 710, in __init__
  
      errread, errwrite)
  
    File "/usr/lib/python2.7/subprocess.py", line 1327, in _execute_child
  
      raise child_exception
  
    OSError: [Errno 2] No such file or directory
  
  </module></module></stdin>

  Why is that happening ? I’m really suspicious : I never mention the names of my pictures ("Image0.jpeg", "Image1.jpeg", ..., "Image499.jpeg", "Image500.jpeg"). Any help will be greatly appreciated !

  P.S. The guy in the tutorial also says that some codecs require a bitrate ; I tried that and it didn’t work either.

• avcodec/zlib_wrapper : Add wrappers for zlib inflateInit, inflateEnd

  15 mars 2022, par Andreas Rheinhardt

  avcodec/zlib_wrapper : Add wrappers for zlib inflateInit, inflateEnd
  It is not documented to be safe to call inflateEnd() on a z_stream
  
  that has never been successfully been initialized by inflateInit(),
  
  but just zeroed. It just happens to work and several codecs rely
  
  on this (they have FF_CODEC_CAP_INIT_CLEANUP set and even call
  
  inflateEnd() when inflateInit() failed or has never been called).
  
  To avoid this, other codecs recorded whether their zstream has been
  
  initialized successfully or not.
  This commit adds wrappers for inflateInit() and inflateEnd() that
  
  do what these other codecs do ; furthermore, they also take care of
  
  properly setting up the zstream before inflateInit() and emit
  
  an error message in case of error.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] configure
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/zlib_wrapper.c
  • [DH] libavcodec/zlib_wrapper.h

• Use ffmpeg libraries to convert stream formats

  17 septembre 2021, par Syrinx

  I'm attempting to write a small program and link it to a minimal set of ffmpeg libraries, like libavformat and whatever other libraries I need.

  


  I am looking for documentation to get me started, or maybe a quick fix to the example program I am using.

  


  I know ffmpeg (the project) provides example programs to help developers get started. I'm using the transcoding example, as it's close to my end goal, but it exits during init with an error about an audio issue.

  


  Here I am using the transcoding example program that come with ffmpeg v4.4, on Ubuntu 18.04. My input source has one video channel (h264) and one audio channel (pcm_mulaw).

  


  $ LD_LIBRARY_PATH=../../dist/lib ./transcoding rtsp://ip-camera/stream out.flv
...
  Stream #0:0: Video: h264, yuv420p, 1280x720, q=2-31, 20 tbn
  Stream #0:1: Audio: pcm_mulaw, 8000 Hz, 0 channels, s16
auto_resampler_0 @ 0x55da787fa140] [SWR @ 0x55da787fa5c0] Rematrix is needed between mono and 0 channels but there is not enough information to do it
[auto_resampler_0 @ 0x55da787fa140] Failed to configure output pad on auto_resampler_0


  


  In libswresample/swresample.c :

  


  320      if ((!s->out_ch_layout || !s->in_ch_layout) && s->used_ch_count != s->out.ch_count && !s->rematrix_custom) {
321          av_log(s, AV_LOG_ERROR, "Rematrix is needed between %s and %s "
322                 "but there is not enough information to do it\n", l1, l2);
323          ret = AVERROR(EINVAL);
324          goto fail;
325      }


  


  I'd really like it if I could make the transcoding example program work (fix it, or maybe use it appropriately if I am misunderstanding something). But short of that, where should I look for documentation about using the ffmpeg libraries ?

  


  I don't even care about the audio. If I can just disable the audio, I would be happy with that solution. I tried tracking the "-an" option to ffmpeg (the program) to see how it does that in source code, but the options handling is a mess and I can't distinguish the parts of the code that I need from all the noise.

  


  ffmpeg has web pages like this that aren't useful at all. There is documentation in the source code that looks like it should be viewed as HTML, but I don't see it exported anywhere. "make doc" generates a very small set of man pages that are insufficient to get me started.