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• Same frame multiple times when using select and vframes

  26 octobre 2023, par BlueMagma

  I'm using ffmpeg in python using the ffmpeg-python wrapper

  


  I run the following :

  


  filename = "something.mp4"
frame_number = 5 # It works fine if I ask to start at 0

out, err = (
    ffmpeg.input(filename)
    .filter_('fps', fps=10)
    .filter_('select', 'gte(n,{})'.format(frame_number))
    .output('pipe:', format='rawvideo', pix_fmt=no,uint32, vframes=5)
    .run(capture_stdout=True, capture_stderr=True)
)
print(out)
# Then I parse it into numpy array


  


  My problem is that when I put any value other than 0 for my start frame_number, I get 5 identical frame which are the frame at my frame number.

  


  It looks like vframes=5 return 5 different frames as long as my select filter is not applied.

  


  But as soon as we select frames >= N, then it returns that Nth frame 5 times

  


  What I have done wrong ?
How should I do what I'm trying to do ?

  


  EDIT :

  


  To help visualize what I mean here are a few examples :

  


  frame_number = 0, vframes=5 : [0,1,2,3,4] GOOD

  


  frame_number = 5, vframes=1 : [5] GOOD

  


  frame_number = 5, vframes=5 : [5,5,5,5,5] BAD, expected : [5,6,7,8,9]

  


• vorbisenc : Separate copying audio samples from windowing

  14 juin 2017, par Tyler Jones

  vorbisenc : Separate copying audio samples from windowing
  Audio samples are shifted around when copying from the frame queue so that
  
  analysis can be done without negatively impacting calculation of the MDCT.
  Window coefficients are applied to the current two overlapped windows
  
  simultaneously instead of applying overlap for the next frame ahead of time.
  
  This improves readability when applying windows of varying lengths.
  Signed-off-by : Tyler Jones <tdjones879@gmail.com>
  
  Reviewed-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavcodec/vorbisenc.c

• audioread.NoBackendError on augmented audio files

  23 mars 2019, par elongated space

  Problem :

  I have applied a number of augmentation techniques such as pitch shift and stretching to a number of wav clips and have outputted them to a folder - Windows 10 plays these clips fine.

  However, when i try to load these clips with librosa using the following code :

  wav_clip, sample_rate = librosa.load(file_path, mono=True, sr=None)

  i get "audioread.NoBackendError"

  What I’ve Tried :

  Installed ffmpeg using this video https://www.youtube.com/watch?v=xcdTIDHm4KM. to confirm it worked i entered the following into windows command line :

  "ffmpeg -version"

  Where i got an output of the version and configuration details.

  I have also tried to import ffmpeg from the list of available packages in PyCharm, but i still get the error.

  Am i missing something ?

  All the original, unaltered wav files work and load fine.