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What I need

I am working on a music player with a sample analyzer. My issue is that I am currently using pydub to get the samples from the song, but as the song gets longer, the more out of sync the two become. I have made the two literally in sync, pydub just so happens to read out of it [I even started them at the same time, the two actually progressively de-synced with audio alone and more so as the song continues playing].

Basically, is there a python-vlc equivalent to pydub.AudioSegment.get_array_of_samples()?

You can look at the python-vlc docs here: https://www.olivieraubert.net/vlc/python-ctypes/doc/

What I've tried

  1. python-vlc has sound.get_time() which returns the last updated time in milliseconds. The issue with this command is not that it only updates every half a second or so [I've found a way around that] but that it doesn't return the accurate time. I can start a timer from when it starts playing using time.monotonic(). As time progresses, the get_time() wildly varies from the timer. I've gotten a difference of 195ms, 294ms and 217ms.

  2. I tried using an external timer using the threading module. It appears that pydub.AudioSegment[index] is not in sync whatsoever.

  3. Scaling from sound.get_time() in py-vlc to len(sound) in pydub. This doesn't work as expected. I cannot tell you why but it is still desynced.

  4. Using sound.get_time() with an average offset that increases over time. It appears that pydub.AudioSegment[index] doesn't line up properly.

  5. Using aubio. It only reads WAV files, and for a live analyzer, converting to a WAV first would take too long.

Things I found out

  • I've looked at how long each song is in milliseconds, len(sound) for pydub and sound.get_length() for python-vlc is different usually by 10 or so seconds.

Things that won't work

  • Using pydub's play() command. I don't like it because it's very limiting.
  • Using something else than py-vlc to play the audio, VLC has many features that just cannot be replicated.

Previous suggestions

I'm curious

  • Is there a python module for Audacity? I've been looking and couldn't find it. I can also use some other command line tool that can interact with Audacity if possible [I know the built in command line utility doesn't do much at all]
VoxelPrismatic
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1 Answers1

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You probably want to use ffmpeg directly for this.

mfkl
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  • How can I use it? I know I can use `subprocess.run([...], capture_output = True)` but what command in ffmpeg do I use? – VoxelPrismatic Sep 25 '20 at 17:46
  • something like https://stackoverflow.com/questions/9913032/how-can-i-extract-audio-from-video-with-ffmpeg maybe – mfkl Sep 28 '20 at 07:33
  • I'm not trying to extract audio, I'm trying to get audio sample data like `pydub.AudioSegment.get_array_of_samples()`. I'm already working with audio files anyway. – VoxelPrismatic Sep 28 '20 at 15:39