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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 Fisch@discuss.tchncs.de to c/linux@lemmy.ml
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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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[-] Supermariofan67@programming.dev 2 points 4 months ago

PNG is a rather slow algorithm based on the DEFLATE compression from zip/gzip. You could extract to bmp or some other uncompressed format. First, to ensure it is lossless, make sure it supports the video's pix_fmt without needing conversion.

[-] Fisch@discuss.tchncs.de 2 points 4 months ago

Using bmp has the same bottleneck as png, which is the write speed of the hard drive

[-] cmnybo@discuss.tchncs.de 5 points 4 months ago

Well, you found your problem then. You will need to get a decent quality SSD to speed it up. Avoid those cheap QLC SSDs, they are slower than mechanical hard drives once the SLC cache fills up.

[-] Fisch@discuss.tchncs.de 0 points 4 months ago

I don't really wanna buy another SSD just for this. I already have two SSDs in my PC, I just don't have enough storage left. All the frames are gonna be like 300gb.

[-] drwankingstein@lemmy.dbzer0.com 1 points 4 months ago

going from YUV->RGB wont incur any meaningful loss, going from RGB -> YUV on the other hand can, but it's rare that it will actually happen so long as you arent messing up your bitdepth too much

this post was submitted on 14 Jul 2024
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