Question / Help GPU Encoding: CPU Importance

[Mads Magnus Kristensen]

Hi

So I have a rather simple question that I was wondering if anyone could answer or atleast give me some insight on.

How much does the CPU say when you are using GPU encoding such as NVENC or AMD VCE? Because right now I see a lot of people justifying purchases of i7 over i5 with "streaming" or "recording". I do understand that an i7 will be way better at encoding when using CPU encoding, but in this case - really how much does it matter? GPU encoding seems superior in all aspects, perhaps except some opinions upon quality of the output?

Anyway.. Yeah I need a place to vent / talk about this. Participation would be greatly appreciated <3

 

[Sapiens]

It matters as much as you care about having decent quality. Hardware encoding via QSV/NVENC/VCE is great at reducing system load for things like local recording but the quality compared to x264 at the same bitrate is poor. When bitrate isn't an issue (local recording) you can just compensate by increasing it, but for streaming you want the best quality you can get within a fairly limited amount of space, usually 3500 Kbps or less.

 

[alpinlol]

Quick rough Comparison
x264 720p30 2000Bitrate (okay Quality)
NVENC 720p30 3500Bitrate (okay Quality)
QSV 720p30 ~2500-3000 Bitrate (okay Quality)

For Recording, like Sapiens already mentioned, it doesnt really matter since you can just feed the either Encoder with more Bitrate.

If you dont want to OC or jump onto DDR4 theres always the Option to go with a Xeon e3 1231v3 which is almost equal to the i7 4790 when it comes to Encoding but for 100$ less

 

[Boildown]

The quality per bit of hardware encoders are generally pretty bad. Haswell and later quicksync can be acceptable, but in most cases when you're bitrate constrained (i.e. sending to Twitch at the bitrates Twitch allows) you get the best results by doing software encoding with x264.

When you have as much bitrate as you please, because you're saving to a hard drive, that's when hardware encoders like NVEnc/Quicksync/VCE are a good or the best option. Because you can make up for their poorer quality per bitrate by adding so many bits that it doesn't even matter.