1 Topic by OpenSourceAnarchist (edited by OpenSourceAnarchist 12-06-2019 00:17:14)

Topic: Optimal SVPcode parameters?

I know video encoding is a subjective, messy topic when talking about "optimal" quality, but I am trying to understand this from the SVP point of view.

I'm getting a new laptop soon with an i5-8365U CPU and Intel UHD 620 iGPU. I will install either Gentoo or Arch Linux on it... Shouldn't matter as they both support the new "Intel-Neo" OpenCL and "Intel-Media-Driver" for VAAPI.

My goal will be to use SVPcode to re-encode somewhat lossy x264/x265 1080p content (not going to lie, acquired through "online sources"...) to H.265. I'd like to use FFmpeg's hevc_vaapi encoder to do so since it is way easier to set up than QSV (and still open-source).

Obviously, I want to avoid quality loss. Inserting interpolated frames adds to a file's data so I expect the resulting file to be larger than my source. How can I ensure the re-encoded file is minimally affected by the hevc_vaapi encoder? I assume setting "hevc_vaapi -q:v 18" and the other necessary options is good enough for no noticeable quality loss... Am I missing something?

Any help is greatly appreciated! :)

  • MAG79
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Re: Optimal SVPcode parameters?

As consumer you can try different algos and compression ratios. Then compare frame-to-frame with your eyes. If you don't see any difference then it is mean you've got nice result.
SVPCode has default algo and compression ratio is CRF 18. It is most usable. it is "-crf 18" parameter for ffmpeg encoder.
I don't know what "-q:v 18" means. Is it the same?

Re: Optimal SVPcode parameters?

Thanks for letting me know. Yeah the vaapi encoders for FFmpeg take different arguments than the software encoders. It has a CRF mode that you can explicitly enable. Sounds like that's a starting point for some basic comparisons!

4 Reply by James D (edited by James D 12-06-2019 12:05:05)

  • Thanks: 97

Re: Optimal SVPcode parameters?

If you use HEVC then it's better to set CRF level to 16 instead of 18. Also, because of different Hz modes for TVs (60/72/120/144) it is questionable to reencode all your library into interpolated frame rate e.g. 24 to 72fps is the best ratio factor and would be great for 72Hz/144Hz and possibly even still better for 120Hz than interpolated 24 to 60fps but takes 3x frames to decode. While 60Hz displays better work with 60 fps.
I look at SVP encode as more of a temporary encode for watching later on mobile devices or while being on a trip with on-the-battery way of using your devices. With further deletion files.