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points by doublepg23 10 hours ago | 0 comments

What is the purpose of lossless H.264 vs. ProRes or the like?

Is it similar to lossless audio were there's not a ton of optimization you can do?

I've attempted to get researchers to use lossless H.264 to encode CT scans. They typically use directories full of tiffs. Even with intra-slice compression (i.e. tiff compression) they are pretty huge. But H.264 will let you recover the original images to the individual bit, and save a huge amount of space thanks to inter-slice similarities.

They are still using directories of tiff, though.

[–] jedbrooke 8 hours ago

I’d imagine the main drawback of using H.264 here is that you’d still have to decode to get the frames back. This is similar to how even though many consumer grade cameras will output natively to h.264, if you want to edit the videos from it you’d usually have to convert it to prores or something first (the editor would usually do this automatically behind the scenes)

I’m not sure if lossless h.264 is I only or not, but if it uses inter-frame compression then it’s difficult to randomly access arbitrary frames. For any arbitrary frame you’d have to find the nearest key frame, then interpolate from there based on the inter-frame compression metadata.

[–] freeone3000 10 hours ago

Lots of hardware requires specifically h.264 as a transit; many of the MPEG standards are built around it. So this lets you get MPEG-PS, or lossless BDs, or some hardware/specialized software decoders for machines that otherwise couldn’t keep up (like set top boxes).

[–] Sopel 9 hours ago

prores is not lossless. It's also an intraframe codec so compression is not great.

[–] ErroneousBosh 6 hours ago

It depends what you mean by "not great". Prores's compression is far better than say H.264, if you actually want usable footage for editing.