Re:How Facebook encodes videos
by paulmd on Monday April 26, 2021 @01:25AM
(#26939468)
NVENC beats x264 medium. Not quite up to the level of the "slow" presets yet but you have to throw a huge amount of hardware at it to match them let alone beat them. Basically the number I came up with a few weeks ago from playing around with x264 settings on ffmpeg was between 6 and 12 cores to keep up with NVENC at 720p and 1080p, depending on framerate and the quality preset.
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What sort of bitrate are we talking about? I haven't tried using NVENC for years and last time I check it was clearly missing many details that x264 tries to preserve.
NVENC is good at cleaning the noise and fast encoding. ( Or basically Game Streaming ). Which isn't something you want to do if you want to do movies encoding.
Re:How Facebook encodes videos
by Wowfunhappy on Monday April 26, 2021 @01:13PM
(#26945090)
> but you have to throw a huge amount of hardware at it to match them let alone beat them.
Sure, and I think hardware encoders are great when you need speed, certainly for real-time video. But in other cases, well, the medium preset sucks. I always encode videos at `veryslow`, and there's just no way to get close to that with a gpu.
Re:How Facebook encodes videos
by BlueTemplar on Monday April 26, 2021 @09:00PM
(#26950426)
How come ? This looks like to be easily parallelised, so GPUs should wipe the floor with CPUs ?
Video encoding isn't GPU-parallelizable. It's a good fit for either CPU+SIMD or custom ASICs. It's just a kind of compression, which means it's based on unpredictable if-statements, which is just what GPUs don't do.
You can mass parallelize it by encoding different clips on different CPUs, this is more optimal because it has less communication overhead.
Re:How Facebook encodes videos
by Wowfunhappy on Monday April 26, 2021 @09:20PM
(#26950613)
No idea, maybe it will change some day. But right now, if you want the best quality at the smallest filesize, nothing seems to come close to the best software encoders. Maybe x264 and x265 are just really good.
They're unusually good because 1. encoding research wasn't done on a business schedule 2. isn't done according to objective metrics (the main ones used, SSIM/PSNR, suck and you have to use human raters) 3. more varied and weirder testcases (some pirated movies, some video game screen recording, more anime).
There's a lot of other free video encoding tools, like avisynth plugins, that are just better than all professional tools. I'm not sure why this is, maybe customers aren't sophisticated enough.
Re:How Facebook encodes videos
by BlueTemplar on Tuesday April 27, 2021 @04:15AM
(#26953360)
What about AV1 ?