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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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Extracting frames from a video with ffmpeg very slow if not using jpeg (discuss.tchncs.de)

submitted 4 months ago by [email protected] to c/[email protected]

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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.

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[–] [email protected] 2 points 4 months ago* (last edited 4 months ago) (1 children)

A) I actually didn't know about this before, do you know what option I need to use in ffmpeg to set the effort?

B) I tried those but it's the same issue as with png, that the hard drive's write speed is too slow (or it's the USB 3 connection but the result is the same)

Edit: Just found out how to set the effort. Setting it to 1 is quite a bit faster but still slow at only 3.8 fps.

[–] [email protected] 2 points 4 months ago* (last edited 4 months ago) (1 children)

what are your system specs? at a low effort you should be getting a lot more FPS, what cli command are you using? but I guess it would be best for you to export to /tmp given enough ram and then go from there

EDIT: for context, when encoding libjxl I would do -distance 0 -effort 2 for lossless output

[–] [email protected] 2 points 4 months ago

I have a Ryzen 5 3600. My command was ffmpeg -i video.mp4 -threads 12 -distance 0 -effort 1 extract/%06d.jxl.