Recherche avancée

Sur d’autres sites (4994)

• Livestream WebVTT with HLS

  10 novembre 2022, par kltye

  I've implemented an HLS service with ffmpeg (which pulls a live stream from nginx-rtmp). That all works fine, but now I'm wondering what kind of programming pattern I should be using to get live captioning to work.

  


  I'm planning on using ffmpeg to output the incoming mp4 stream to multiple WAV chunks (i.e., the same way HLS fMP4 parts are created), and then sending those chunks over to Azure Cognitive Services for speech-to-text recognition. My question is, what do I do when I receive the speech results ? Do I dump that vtt file into the same directory as my HLS chunks, and then serve that up using a single m3u8 file (with audio/video tracks along with the text track) ?

  


  Currently ffmpeg is updating the m3u8 playlist for HLS clients ; would it be possible for me to create the m3u8 playlist just for the vtt files, and serve that concurrently with the "regular" HLS playlist ? Also, time synchronization would seem to be difficult, because I'll be sending discrete WAV files over to Azure, so the vtt timestamps are going to be relative to the chunk I'm sending.

  


  Help ! I've done searches online, and I grasp the various issues, but I'm not sure how to plumb them all together.

  


• FFMPEG : Get the Scene Change Detection value for all frame

  19 novembre 2016, par celacanto

  I’m trying to measure how much a movies is "fast" (more action in the screen and quick scene chances). I don’t want just a single value for the movie, but values along the movie to see how the action varies during it. After normalize the frame rate of the movies (10 fps), my idea is to compare each frame with the previous. I’m not only interest if the scene has changed, but also, if there was no cut, how much movement there is. Not only people/object movement but also, camera movement. In summary the paced (I think that the term) of the scenes.

  My idea was to use the scene function from ffmpeg as a metric. But looking at the document and examples online I’m thinking I can only use the value of the Scene Change Detection as a threshold to return frames informations, but I can’t get ffmpeg to return the value. Is that right ? There is any way I can make it return the value ?

• How to grab specific segments of M3U8 via ffmpeg ?

  30 juillet 2020, par Lysander Cox

  I recently asked baout how I could download segments of an online m3u8 file, and someone pointed out that this could be accomplished via ffmpeg :

  


  ffmpeg -i [LINK] -codec copy [OUTPUT FILE] #downloads only audio segments;
ffmpeg -i [LINK] -bsf:a aac_adtstoasc -vcodec copy -c copy -crf 50 [OUTPUT] #downloads audio and video segments


  


  For those who aren't familiar, m3u8 is formatted kinda of like a "playlist", with an m3u8 file pointing to a bunch of smaller "segments" which are pieced together to form the whole of the video. As a result, it's completely possible to halt the above commands partway through their execution and still produce a watchable video (i.e. one that will be interpreted correctly by video editors).

  


  I'm wondering if there's a built-in method with ffmpeg that allows me to grab segments N-M of a given m3u8. If there are methods outside of ffmpeg, feel free to mention them as well. Thanks for the help.