I can't figure out how preanalisys works on an AMF encoder

[sandrix]

Hi. Immediately I ask you to excuse me if the question is not appropriate, but I will be grateful if you tell me where I can ask it or maybe you can help me.

I have a Radeon RX570 on my second PC that I use exclusively for various tests. Radeon graphics card owners are well aware that the AMD H.264 encoder is low performance and needs to be properly configured to avoid overloading the encoder. Especially if it's VCE 3.0

Quite a long time ago I found a compromise. Setting the parameter preanalisys=0, which reduces the load on the encoder by about 10%. I had an argument and I just want to know the truth. My opponent claims preanalysis=0 is not even a valid parameter and doesn't work. There is EnablePreAnalysis=false for this, which I agree with, but disagree that preanalysis=0 doesn't work. In turn, EnablePreAnalysis=true does not make any changes to the behavior of the encoder. However, I'm not saying it doesn't work. Theoretically, the load should increase, but this does not happen.

Without any parameters, the load on the encoder varies greatly and reaches critical values, with preanalysis=1, 100% encoder overload. With peanalysis=0, the encoder works smoothly, there are no overloads.

What am I wrong about and why is this happening?

 

[koala]

According to the ffmpeg h264_amf help (see https://gist.github.com/nico-lab/94ded6ded780208e35d663001bbeadb7) the parameter preanalysis=<bool> is correct usage, while EnablePreAnalysis=... doesn't exist. Bool means the value is true or false (1 or 0).

Default value is false, so preanalysis=false is the same as not set at all.
There is no 3rd option value. Not set is the same as false.

 

[sandrix]

You're right, the default setting is disabled, but after 3-5 minutes of running I always get GPU and encoder utilization up to 100% unless peanalysis=0 is specified. At the same time, RTSS indicates other data. It is very strange.

 

[sandrix]

If someone needs it. I ran some more tests on my RX 570 (VCE 3.0) and confirm that preanalysis=0 allows the AMD HW H.264 encoder to run smoothly and record/stream at FHD 60fps without overload. Anyway, that's how it works for me. It's stupid, but it works. The quality is just terrible, so it's better to use resolutions of 720p, 864p, 900p, 936p (less is better quality) if streaming on twitch. For video recording and streaming on YouTube, it is best to use AMD H.265 / HEVC, it is much better in terms of quality and performance.

This is a problem on older graphics cards, but nothing to be done.

 

[AalaAzimi]

I've been messing around with the pre analysis commands and I've been reading through the documentation on both AMF and FFmpeg, apparently preanalysis is set to auto by default so I think what's happening is that it might turn on and off by itself and I'm not entirely sure what its requirements are for it to turn on/off, which is why when you declare it as off it will stay off.