Intel SVT-AV1

[benwaggoner]

Originally Posted by GeoffreyA

I think the problem is temporal or keyframe filtering, which can get even worse in libaom. SVT-AV1-PSY seems to have largely overcome it, but is, perhaps, still constrained by AV1's nature. VVC, through vvenc, comes out even worse in this regard. It's also disaster for many of these encoders, x264 included, in two-pass mode. x265's rate control was solid in two passes.

That kind of temporal discontinuity has always been an encoder problem, not a codec problem, in my experience. We even had it working well in WMV9 Advanced Profile/VC-1, where we got interframe delta QP for I-frames enabled (it was only P and B in WMV9 Main; an oversight).

[benwaggoner]

Originally Posted by Z2697

With FFmpeg, that's the default behavior, or maybe the only behavior, as the bitdepth conversion code of x265 is not included in the "core encoding function" that FFmpeg wraps around, it will only try to keep the input pixel format, the profile is automatically determined based on that.
That's probably also how almost all of the encoders in FFmpeg works, when some input formats not supported by an encoder, the pixel format conversion is done by auto-insterted swscale filter.
So if the x265 library that linked to FFmpeg is compiled with 10bit support, Main10 profile will be used in this case. The profile parameter doesn't work, even if you specified Main10, but input 8bit, the result is Main profile.

Oh, that's annoying! I didn't realize as I always pipe to x265 when I am using ffmpeg, so I can use the same x265 syntax regardless of the host app.

[benwaggoner]

Originally Posted by GeoffreyA

IYesterday, I tested this out, and found that disabling TF and the loop filters did not eliminate the temporal "flickering," squaring with your notes that psy-rd was key.

Yeah, all low-moderate bitrate video encoding quality is reliant on having psychovisual rate distortion. Reference encoder style fixed GP at fixed QP is useful for early stage development, but never delivers actual real-world quality @ bitrate improvements compared to what a refined encoder for a prior generation codec can deliver.

Video codecs are psychovisual optimizations all the way down, including such basic elements like sRGB, gamma, and quant/lambda tables. Even an uncompressed .BMP file relies on embedded psychovisual optimization to get an 8-bit value to reasonably map to human visual perception.