cross-posted from: https://discuss.tchncs.de/post/18870157

I’m trying to extract the frames of a video as individual images but it’s really slow, except when I’m using jpeg. The obvious issue with jpegs is the data loss from the compression, I want the images to be lossless. Extracting them as jpegs manages about 50-70 fps but as pngs it’s only 4 fps and it seems to continue getting slower, after 1 minute of the 11 minute video it’s only 3.5 fps.

I suspect it’s because I’m doing this on an external 5tb hard drive, connected over USB 3.0 and the write speed can’t keep up. So my idea was to use a different image format. I tried lossless jpeg xl and lossless webp but both of them are even slower, only managing to extract at about 0.5 fps or something. I have no idea why that’s so slow, the files are a lot smaller than png, so it can’t be because of the write speed.

I would appreciate it if anyone could help me with this.

  • MelastSB@sh.itjust.works
    1·
    4 个月前

    I guess you could check the size of the lossless and lossy frames it outputs, to convert the fps to Mbps. If both values are similar then it’s probably the drive

    • Fisch@discuss.tchncs.deOPEnglish
      2·
      4 个月前

      I just did a rough calculation where I did estimated size of png / estimated size of jpg * fps of png and the value was roughly in the ballpark of what the fps for jpg were, so I’m very sure it’s the drive