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• Python - How do I extract audio and video from the same parts of a file ?

  18 juillet 2018, par mplis

  My goal is to analyze a video file (in this case an mp4 file) for the occurrence of certain features and create a new video file that just contains the video and audio from slightly before and slightly after those features occurring.

  I’m using Python/OpenCV and can correctly identify the features in the video and can create the new video file that I want.

  I can also use the subprocess module and ffmpeg to extract the full audio from the original file and I can use the wave module to iterate over the audio frames. I’m also planning to use ffmpeg to combine the resulting audio and video files.

  My issue is extracting the audio that matches up with the frames in the new, condensed video file. The number of frames in the original video file (according to OpenCV) doesn’t equal the number of frames returned from Wave.getnframes(), so I’m not sure how to extract just the audio that I need.

• Python - How do I extract audio and video from the same parts of a file ?

  3 février 2016, par mplis

  My goal is to analyze a video file (in this case an mp4 file) for the occurrence of certain features and create a new video file that just contains the video and audio from slightly before and slightly after those features occurring.

  I’m using Python/OpenCV and can correctly identify the features in the video and can create the new video file that I want.

  I can also use the subprocess module and ffmpeg to extract the full audio from the original file and I can use the wave module to iterate over the audio frames. I’m also planning to use ffmpeg to combine the resulting audio and video files.

  My issue is extracting the audio that matches up with the frames in the new, condensed video file. The number of frames in the original video file (according to OpenCV) doesn’t equal the number of frames returned from Wave.getnframes(), so I’m not sure how to extract just the audio that I need.

• Converting WebM audio to mp3 using ffmpeg and Rails

  30 avril 2021, par Garrett Bodley

  I created an online step sequencer and want to add functionality so that users can record the audio and save it as an mp3 on their local machine. I've been able to use the WebAudioAPI to record the sound generated in the browser window and send it to my Rails backend as a WebM blob. I am attempting to incorporate ffmpeg using the Streamio gem.

  


  How do I convert that blob to mp3 ? I'm planning on making a Recording model that belongs_to :user and has_one_attached :audio. I imagine I should use a before_save callback to process the blob ? What's confusing to me is that it seems streamio creates a new copy of the file when transcoding. How do I convert the blob to mp3 in place ?

  


  I've seen some posts where people call ffmpeg using system("ffmpeg code goes here") but I don't really understand how to grab the output so that ActiveStorage can link the resulting file to my models and whatnot.

  


  To add complexity to all of this is that I ultimately want to host this publicly and store the audio in a Cloudinary folder, which I imagine would change the process quite a bit. As you can tell I'm a bit confused as to how best to approach this problem. Any help would be greatly appreciated !