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• How to do precise frame cut with ffmpeg ?

  25 juillet 2020, par Menglun Li

  I tried to cut multiple big videos into many small pieces. I know I can cut and export the small pieces one by one with "Premiere Elements", however that takes a lot time to export them manually. I couldn't find a way to do batch export in "Premiere Elements".

  


  I wrote down the starting and ending points of the small videos from Premiere Elements' timeline viewer, then I created a batch file to use ffmpeg for batch cutting. Below is one of the cutting command in the batch file.

  


  ffmpeg -i input.mp4 -ss 00:20:45.09 -to 00:23:01.00 -c:v libx264 -c:a aac output5.mp4 


  


  I compared the video that was cut by ffmpeg and the video was exported by Premiere Elements. I found sometime they are not starting and ending at the same frame, and it is not consistent either. Both the starting and ending frame that was cut by ffmpeg can drift forward or backward 6-9 frames from the frame number showed in Premiere Elements.

  


  How do I make sure ffmpeg has the precise frame cut ? Thanks in advance.

  


• Nginx RTMP - restream rtmp or hls with 1h delay

  15 août 2015, par Michał Paduch

  I want to show users with 1h deley my rtmp stream. How to accomplish this task ?
  I think about solution :
  input : rtmp ://stream...
  Record input into small files, e.g such way :

  recorder chunked {
  
              record all;
  
              record_interval 15s;
  
              record_suffix -%Y-%m-%d-%H%M.flv;
  
              record_path /home/user/capture/chunked;
  
          }

  Then only how to stream again this small files with hls or rtmp back to end user ?

• Seeking Guidance on Audio Development Libraries for Playing Various Music Formats on iOS [closed]

  3 décembre 2023, par FaiChou

  I am exploring audio development and am overwhelmed by the numerous libraries available :

  


  

  • AVFoundation

  


  • MediaPlayer

  


  • AVFAudio

  


  • Audio Engine

  


  • CoreAudio

  


  • AudioToolbox

  


  • Audio Unit

  


  


  Which of these should I use to play both network or local music files (flac/wav/mp3/aac/wma/ogg) ? What are their specific roles ?

  


  My understanding is that I should use ffmpeg for demuxing to unpackage, then decode the stream to get PCM samples, possibly using Audio Engine for playback. Is this a software decoding method ? For Apple-supported formats like mp3, can I bypass ffmpeg for decoding ? Which library would be most suitable in this case ?

  


  Additionally, how do I extract metadata (song name, artist, cover, lyrics, etc.) from music files ? Apple's own solutions seem to support only ID3 or iTunes tags. How should I handle other formats like wav/flac ?

  


  The two links below are the resources I've referenced, but they seem outdated. My search for newer, reliable explanations has been fruitless.

  


  

  • whats-the-difference-between-the-apple-audio-frameworks

  


  • Core Audio Essentials