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• How do I copy ALL metadata from flac/mp3 to alac with ffmpeg ? -movflags isn't working, default just copies basic metadata

  24 juillet 2021, par Architekt

  I've spent 2 days now reasearching this and all the info I've found doesn't work. If I do this simple command :

  


  ffmpeg -i test.mp3 -y -vn -c:a alac /storage/test.m4a


  


  it copies the standard tags. The -vn is to disable copying album art, I've given up on that. It's easier to just separately use AtomicParsley to handle it because some of the album art isn't height divisble by 2.

  


  Problem is, I have extra custom tags that I need as well. Not necessarily for this particular track, but for all the vinyl I spent 2 months archiving. I've tried using the -movflags use_metadata_tags option but that didn't do anything. In fact, it completely prevented the copying of any metadata whatsoever. Here's the command I tried :

  


  ffmpeg -i test.mp3 -y -movflags use_metadata_tags -vn -c:a alac /storage/test.m4a


  


  On my Windows machine, if I use Foobar2000 and convert the same file to m4a, it copies ALL metadata, 100% to the resultant m4a file. Sadly, I need to do this from a linux command line, as part of an automation process. Both commands I've tried show output metadata equivalent to the input (sans cover art), so I'm not sure what that's about. In case it helps, here's the full screen output when I use that latter command with the -movflags tag. I'm going to use a pastebin link so as to not clutter this post with the verbose output.

  


  I've tried -map_metadata 0 as well, same results, but that's to be expected as from what I've read that just copies the global/standard tags. This must be possible, otherwise I have no idea how foobar2000 would be able to do it. I'd love to just use that, but alas, as stated, I have to do this on Linux command line for this particular situation.

  


• How to write to H264 .mp4 file from Ubuntu with Python OpenCV VideoWriter, FOURCC

  12 septembre 2022, par kevinlinxc

  I am on Ubuntu 18.04, but the solution has to generalize to Debian Buster because that's what Streamlit.io Sharing websites runs on.

  


  I want to write frames with Python OpenCV to a h.264 encoded mp4 file.

  


  It has to be h.264 so that it can be shown on the web, and it has to be mp4 because it's the most common video file type.

  


  I am struggling to find a FOURCC code that works for these exact requirements. The code goes here :

  


  out = cv2.VideoWriter(output_name, cv2.VideoWriter_fourcc(*'X264'), fps, insize)

  


  I have tried avc1 and avc3, which yield Could not find encoder for codec_id=27, error: Encoder not found

  


  Note that avc1 works fine on Windows when the cisco-provided file openh264-1.8.0-win64.dll is in the same directory as the python file, but having the Linux equivalent libopenh264-1.8.0-linux64.so does not make it work on Ubuntu.

  


  H264 and X264 fail with 'H264' is not supported with codec id 27 and format 'mp4 / MP4 (MPEG-4 Part 14)'

  


  I have installed ffmpeg, x264, and libx264-dev with sudo apt-get install, but they do not change the outcome whatsover as the comment on here here says.

  


  One possible lead I have is to compile ffmpeg with 264 enabled, but I'm unfamiliar and I'm not confident I could replicate it on Streamlit, since I can't just ssh in and run commands.

  


  Is it just impossible to encode h.264 on mp4 on Linux with Python OpenCV ? This seems like it should be doable, but I've hit many dead ends.

  


• Converting wav to wav ulaw from Python

  1er septembre 2021, par Powlow

  Trying to convert a wav file to a wav uLaw in python.

  


  Using pydub's AudioSegment I am able to convert to mp3 using the following :

  


  AudioSegment.from_wav(fromFile).export(toFile, format="mp3", bitrate="128k")


  


  What would be the equivalent for wav uLaw using the ffmpeg pcm_mulaw codec and specifying 8bit, 8kHz ?

  


  The command using ffmpeg directly is :

  


  ffmpeg -i 1.wav -c:a pcm_mulaw -ar 8000 1ulaw.wav

  


  Can't find a reference to how to use codecs specifically in Python with pydub. Have found some examples but they mention a few specific cases and then mention you can use anything ffmpeg can handle but without any reference to how to reference codecs.