Re: [FFmpeg-devel] [PATCH] avcodec/nvenc: High bit depth encoding for HEVC

From: Timo Rothenpieler <timo@rothenpieler.org>
To: Roman Arzumanyan <r.arzumanyan@visionlabs.ai>,
	FFmpeg development discussions and patches
	<ffmpeg-devel@ffmpeg.org>
Cc: Diego Felix de Souza <ddesouza@nvidia.com>
Subject: Re: [FFmpeg-devel] [PATCH] avcodec/nvenc: High bit depth encoding for HEVC
Date: Thu, 18 Apr 2024 15:33:06 +0200
Message-ID: <2540329d-79aa-4996-a566-b7b55299de0c@rothenpieler.org> (raw)
In-Reply-To: <CAJZRZVk+YN1e8FaLqLA1may9RJHD4-RyLS4hOvkz4GKRds0_jg@mail.gmail.com>

On 18/04/2024 14:29, Roman Arzumanyan wrote:
> Hi Diego,
> Asking for my own education.
> 
> As far as you've explained, the 8 > 10 bit conversion happens within the 
> driver, that's understandable.
> But how does it influence the output? Does it perform some sort of 
> proprietary SDR > HDR conversion under the hood that maps the ranges? 
> What's gonna be the user observable difference between these 2 scenarios?
> 1) 8 bit input > HEVC 8 bit profile > 8 bit HEVC output
> 2) 8 bit input > 10 bit up conversion > HEVC 10 bit profile > 10 bit 
> HEVC output
> 
> Better visual quality? Smaller compressed file size?
> In other words, what's the purpose of this feature except enabling new 
> Video Codec SDK capability?

Video Codecs tend to be more efficient with 10 bit, even if it's just 8 
bit content that's been up-converted to 10 bit.
I.e. yes, it'll (Or can, at least. Not sure if it's a given.) produce 
smaller/higher quality content for the same input.

As for the exact reason, I can't explain, but it's a well known concept.
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