I haven't actually done the comparison myself, but the common refrain is that the quality of the video suffers when you use GPU accelerated encoding. That's not a tradeoff I want to make, so I've just stuck with CPU encoding.
Every single encoder, regardless or hardware or software will output different output quality. Video Encoding is a lossy encoding, not lossless like ZIP or RAR. That is the same with Audio that is why people test different audio encoder. It seems more people knows this about Audio than Video. At least on HN.
GPU encoding quality has always been lower quality than Software. Primary because they trade off quality for speed. It is good enough once you hit certain bitrate, but at low bitrate where absolutely encoding efficiency is required Hardware Encoding just dont compare to software. Even with Software you could have multiple encoder with different results. It is not like H.266 / HEVC only has x266 as encoder, example Netflix uses BEAMR. And Broadcasting TV station uses other encoder that better suits their needs.
And it is one reason why I dislike all these AV1 discussion, whenever people said it is slow they said use SVT-AV1, well yes SVT-AV1 is faster but dont produce the best AV1 quality encode. So what is the point. It is like every time these discussions about AV1 AOM supporters will just move the goal post.
GPU video encoding is pretty much always optimised for real-time encoding, meaning that it can't run certain optimisations as it would increase the time to encode.
Compare x264 veryfast and veryslow presets. There is a quality difference at the same bitrate.
Additionally, GPU encoders don't have as many psychovisual options as CPU encoders as they would need to be included in the hardware and adding extra options to CPU encoders is much faster, easier and cheaper.
You could build a non-realtime GPU encoder, but there is not much point.
There two types of GPU acceleration: acceleration by a hardware codec bolted on a GPU, and actual GPU computational acceleration. the latter is not widely used but probably is not n gonna have any difference in terms of quality, and provides only modest acceleration.
I haven't actually done the comparison myself, but the common refrain is that the quality of the video suffers when you use GPU accelerated encoding. That's not a tradeoff I want to make, so I've just stuck with CPU encoding.
Wait, why does GPU encoding affect the output quality? Is that common in transcoding stuff?
>why does GPU encoding affect the output quality
Every single encoder, regardless or hardware or software will output different output quality. Video Encoding is a lossy encoding, not lossless like ZIP or RAR. That is the same with Audio that is why people test different audio encoder. It seems more people knows this about Audio than Video. At least on HN.
GPU encoding quality has always been lower quality than Software. Primary because they trade off quality for speed. It is good enough once you hit certain bitrate, but at low bitrate where absolutely encoding efficiency is required Hardware Encoding just dont compare to software. Even with Software you could have multiple encoder with different results. It is not like H.266 / HEVC only has x266 as encoder, example Netflix uses BEAMR. And Broadcasting TV station uses other encoder that better suits their needs.
And it is one reason why I dislike all these AV1 discussion, whenever people said it is slow they said use SVT-AV1, well yes SVT-AV1 is faster but dont produce the best AV1 quality encode. So what is the point. It is like every time these discussions about AV1 AOM supporters will just move the goal post.
6 replies →
GPU video encoding is pretty much always optimised for real-time encoding, meaning that it can't run certain optimisations as it would increase the time to encode.
Compare x264 veryfast and veryslow presets. There is a quality difference at the same bitrate.
Additionally, GPU encoders don't have as many psychovisual options as CPU encoders as they would need to be included in the hardware and adding extra options to CPU encoders is much faster, easier and cheaper.
You could build a non-realtime GPU encoder, but there is not much point.
There two types of GPU acceleration: acceleration by a hardware codec bolted on a GPU, and actual GPU computational acceleration. the latter is not widely used but probably is not n gonna have any difference in terms of quality, and provides only modest acceleration.