Recherche avancée

Sur d’autres sites (5251)

• extract audio with ffmpeg

  20 décembre 2014, par marcobonny88

  I need to extract audio from many mov file. I have to utilize the audios inside an iOS app, the goal is to have outputs file with low file size weight and perfectly equal sound to the input file.
  So i proceeded extrating audio in this way :

  ffmpeg -i 6.2.mov -vn -acodec aac -strict -2 try.m4a

  The input information :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '6.2.mov':
  
  Metadata:
  
   major_brand     : qt  
  
   minor_version   : 0
  
   compatible_brands: qt  
  
   creation_time   : 2014-12-03 10:12:08
  
   Duration: 00:00:01.58, start: 0.000000, bitrate: 42754 kb/s
  
  Stream #0:0(und): Video: prores (apcn / 0x6E637061), yuv422p10le(bt709), 960x540, 40383 kb/s, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 24k tbn, 24k tbc (default)
  
  Metadata:
  
    creation_time   : 2014-12-03 10:12:08
  
    handler_name    : Core Media Data Handler
  
    encoder         : Apple ProRes 422
  
    timecode        : 00:00:00:00
  
  Stream #0:1(und): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
  
  Metadata:
  
    creation_time   : 2014-12-03 10:12:08
  
    handler_name    : Core Media Data Handler
  
  Stream #0:2(und): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
  
  Metadata:
  
    creation_time   : 2014-12-03 10:12:08
  
    handler_name    : Core Media Data Handler
  
    timecode        : 00:00:00:00

  The output information :

  Output #0, ipod, to 'try.m4a':
  
  Metadata:
  
   major_brand     : qt  
  
   minor_version   : 0
  
   compatible_brands: qt  
  
   encoder         : Lavf56.15.102
  
   Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp (24 bit), 92 kb/s (default)
  
  Metadata:
  
    creation_time   : 2014-12-03 10:12:08
  
    handler_name    : Core Media Data Handler
  
    encoder         : Lavc56.13.100 aac
  
  Stream mapping:
  
    Stream #0:1 -> #0:0 (pcm_s24le (native) -> aac (native))

  The problem is that re encoding pcm_s24le to AAC create an output that cut the some ms at the beginning.

  

  There is a way resolve or go around the problem ? Like padding the output 50ms...
  Helps ?

• Fastest way to extract moving dynamic crop from video using ffmpeg

  5 avril 2024, par NateW

  I'm working on an AI project that involves object detection and action recognition on roughly 30 minute videos.

  


  My pipeline is the following :

  


  

  • determine crops using object detection model

  


  • extract crops using Python and write them to disk as individual images for each frame.

  


  • use action recognition model by inputting a series of the crops.

  


  


  The models are fast but actual writing of the crops to disk is slow. Sure, using an SSD would speed it up but I'm sure ffmpeg would greatly speed it up.

  


  Some of the challenges with the crops :

  


  

  • the output size is always 128x128

  


  • the input size is variable

  


  • the crop moves on every frame

  


  


  My process for extracting crops is simple using cv2.imwrite(output_crop_path, crop) in a for loop.

  


  I've done experiments trying to use sndcommand and filter_complex. I tried this https://stackoverflow.com/a/67508233/4447761 but it outputs an image with black below the crop and the image gets wrapped around on the x axis.

  


  

  


• How to extract video clip from larger video based on specific time and duration

  26 juillet 2022, par user19019404

  I have video clips that get created. Each video is recorded for 5 minutes and starts at a time e.g. 10:01:20 to 10:06:19 then the next video from 10:06:20 etc. These videos are recorded at a specific frame rate, be it 5 frames or 30 frames (its dependent on the platform making the recording). The net result is NOT a 5 minute video clip but might be a 2 minute video clip (where everyone moves very quickly in the view as a result of the frame rates). I cannot restrict a 1 to 1 recording as these are generated by external systems.

  


  I need to extract specific portions out of the video. For example I need to extract from 10:03:10 to 10:03:35 (25 seconds). This would equate to 10 seconds into the video up to 14 seconds into the video, in those 4 seconds of video, 25 real world seconds are displayed.

  


  My question is do you have any guidance as to how I can calculate that each second of recording actually means 10 or 12 seconds in real life, therefore go to this frame and record to this frame for example.

  


  I have been looking at cv2.CAP_PROP_FPS to get the video frame rates, CAP_PROP_POS_MSEC and CAP_PROP_FRAME_COUNT and believe the answer might lie there, but not sure.

  


  The thinking being if I work out the frame rate of the video, the total frames then I can divide the one by the other to get to how many frames make up real world seconds (this is where I fail). This way I can run from frame to frame as a result.

  


  Thank you