Linux

48181 readers

1067 users here now

From Wikipedia, the free encyclopedia

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.

Rules

Posts must be relevant to operating systems running the Linux kernel. GNU/Linux or otherwise.
No misinformation
No NSFW content
No hate speech, bigotry, etc

Related Communities

Community icon by Alpár-Etele Méder, licensed under CC BY 3.0

founded 5 years ago

MODERATORS

[email protected]

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]

28 comments fedilink hide all child comments

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.

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 0 points 4 months ago (1 children)

Actually they both use Discrete Cosign Transform!

PNGs use DEFLATE which is a generic compression standard that exhaustively searches for smaller ways to compact the data.

I would recommend comparing the quality of images of different formats against eachother to see if there is noticeable lossyness.

If the PNGs are indeed better, try to set the initial compression of the PNGs to "zero" and come back later to "crush" them smaller.

[–] [email protected] 1 points 4 months ago (1 children)

Even if they use the same technique, they're entirely different algorithms and h.264 also takes information from multiple different frames, which is why the video is 1.7gb but a folder with each frame saved as a png is over 300gb.

The formats with the best compression, where it might be fine, are jpeg xl and webp, as far as I know. They're even slower tho because they're so CPU intensive and only use one thread.

Setting the png compression to 0 doesn't help because the bottleneck for png is the hard drives write speed. I already tried that.

[–] [email protected] 1 points 4 months ago

Yeah, that makes sense. There might be some useful interface in VAAPI?