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• How to utilize multiprocessing and multithreading efficiently to convert 1000s of video files to audio using python in parallel

  8 février 2021, par Sachin Kumar S

  I tried to convert video files to audio using moviepy python package. it works perfectly fine.
However, I have 1500 100MB sized videos and I want to convert all of them to audio files. It takes a lot of time with the standard approach.

  


  Code to convert one video file to audio :

  


  import moviepy.editor as mp
clip = mp.VideoFileClip('file.mp4') 
clip.audio.write_audiofile(r"file.mp3")


  


  I can also use threading to convert multiple files at the same time but I want to utilize multiprocessing and multithreading both to achieve the result most efficiently with less time complexity.

  


  Algo using threading only :

  


  clip1...clip10= make 10 lists with 150 files names from os.listdir()
spawn 10 threads to process 10 files at a time.

t1= Thread(target=convert, args=(clips1))
.
.
.
t10= Thread(target=convert, args=(clips2))


  


  Any Ideas ?

  


• FFmpeg generates different number of frame for ORIGINAL and CONVERTED files even though they have same duration and frame rate

  24 février 2021, par Mahfujur Rahman

  I have two files with the following configuration. I am extracting frames using FFmpeg and then encoding the frames with MediaCodec using the frame duration to calculate timestamp in android.

  


  While processing the first file, FFmpeg generates around 3000 plus frames but for the second file, FFmpeg generates only around 1500 frames.

  


  As I am using the frame duration to encode video, the output video duration changes for the above case. What is it that I am doing wrong ? And Why FFmpeg generates a different number of frames ?

  


  VID-20210223-WA0009.mp4

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'VID-20210223-WA0009.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42isom
  Duration: 00:00:50.39, start: 0.000000, bitrate: 1410 kb/s
    Stream #0:0(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(tv, bt709), 480x848, 1345 kb/s, 59.96 fps, 59.94 tbr, 600 tbn, 1200 tbc (default)
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 62 kb/s (default)
At least one output file must be specified



  


  


  

  • Frame pts and duration

  


  


  


  VID-20210223-WA0009_1.mp4

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'VID-20210223-WA0009_1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.48.100
  Duration: 00:00:50.39, start: 0.000000, bitrate: 1376 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuvj420p(pc), 480x848, 1301 kb/s, 59.94 fps, 59.94 tbr, 60k tbn, 119.88 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 62 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
At least one output file must be specified



  


  


  

  • Frame Pts and duration

  


  • Converted from the first file using FFmpeg.

  


  


  


• ffmpeg create 2 videos from images with a consistent (exact same) duration

  3 septembre 2021, par danday74

  I have exactly 1500 jpg's named rgb_00000.jpg rgb_00001.jpg etc. Each image has dimensions 1920 x 1440 (aspect ratio 4:3). These images are sequential and represent someone filming a car.

  


  I have exactly 1500 png's named depth_00000.png depth_00001.png etc
Each image has dimensions 256 x 192 (aspect ratio 4:3). These images are sequential and represent a depth visual for the first set of images.

  


  From these 2 sets of images I want to create 2 videos with the exact same length. The user will then be able to flip between videos.

  


  So I ran this command to generate the first video

  


  cat depth_*.png | ffmpeg -y -f image2pipe -framerate 30 -i - -pix_fmt yuv420p -c:v libx264 depth.mp4


  


  Video created with success. Then I ran this command to output duration information

  


  ffprobe -v quiet -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 depth.mp4


  


  The duration was 51.534

  


  I then repeated these exact same commands on the jpg set of images. Again video was created with success. But this time the duration is 51.905

  


  Why is the duration different given an identical frame rate and image count ? How can I make it so that the duration is identical for both videos (to support jumping between them) ?

  


  Note : I don't want to just truncate the videos to the same length since then they would not be parallel and flipping / jumping between the videos would not be smooth

  


  Many thanks