View Single Post
Old 7th January 2021, 02:23   #2382  |  Link
benwaggoner
Moderator
 
Join Date: Jan 2006
Location: Portland, OR
Posts: 4,750
Quote:
Originally Posted by utack View Post
Not sure if ffmpeg currently works inefficently but mpv with an 8K AV1 Video it allocates just over 4000MB VRAM for me, so that would not work
Could someone cross-check with the native Windows Video Player?
There are about 34M pixels in an 8K video frame. And there's no point in non-HDR 8K and HDR will be 10-bit minimum. With 4:2:0 and assuming no bit alignment overhead, that's 2.5 bytes per pixel, about 85M per frame. Of course, there is always bit alignment overhead, and internal high precision frequency transforms could easily make for 48 bits/pixel. Frame-parallel decoding could involve several of those. And a few RGB decoded frames for buffer could be way bigger than that. 16-bits per channel at RGBA 444 would be 272 MB/frame.

HW decoders have an easier time of it because they don't need frame-level parallel decoding nor RGB buffers since they can write 420 straight to GPU. But yeah, 4GB for 8K SW decoder seems quite plausible for me if a decent number of frames need to be buffered at different stages.

None of that is specific to AV1, but AV1 is the only thing people are talking about doing 8K SW decode with. My own research hasn't found any content that actually looks better at 8K than 4K, so there's a whole lot of solution looking for a problem going on in that scenario. 8K YouTube looks better than 4K YouTube because YouTube is bit-starved at every resolution and bitrate
__________________
Ben Waggoner
Principal Video Specialist, Amazon Prime Video

My Compression Book
benwaggoner is offline   Reply With Quote