Re: [FFmpeg-devel] [PATCH v2 2/4] ffmpeg: Add display_matrix option

From: Gyan Doshi <ffmpeg@gyani.pro>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH v2 2/4] ffmpeg: Add display_matrix option
Date: Wed, 17 Aug 2022 14:20:43 +0530
Message-ID: <35f0db7c-0ad8-506b-c09a-7948f79c71eb@gyani.pro> (raw)
In-Reply-To: <166072430421.4001.1353603178221790793@lain.khirnov.net>

On 2022-08-17 01:48 pm, Anton Khirnov wrote:
> Quoting Thilo Borgmann (2022-08-16 20:48:57)
>> Am 16.08.22 um 16:10 schrieb Anton Khirnov:
>>> Quoting Thilo Borgmann (2022-08-15 22:02:09)
>>>> $subject
>>>>
>>>> -Thilo
>>>>   From fe2ff114cb004f897c7774753d9cf28298eba82d Mon Sep 17 00:00:00 2001
>>>> From: =?UTF-8?q?Jan=20Ekstr=C3=B6m?= <jeebjp@gmail.com>
>>>> Date: Mon, 15 Aug 2022 21:09:27 +0200
>>>> Subject: [PATCH v2 2/4] ffmpeg: Add display_matrix option
>>>>
>>>> This enables overriding the rotation as well as horizontal/vertical
>>>> flip state of a specific video stream on the input side.
>>>>
>>>> Additionally, switch the singular test that was utilizing the rotation
>>>> metadata to instead override the input display rotation, thus leading
>>>> to the same result.
>>>> ---
>>> I still don't see how it's better to squash multiple options into a
>>> single option.
>>>
>>> It requires all this extra infrastructure and in the end it's less
>>> user-friendly, because user-understandable things like rotation or flips
>>> are now hidden under "display matrix". How many users would know what a
>>> display matrix is?
>> FWIW I think Gyan's request to do this all in one option that effect one thing (the display matrix) is valid.
> I don't.
>
> It may be one thing internally, but modeling user interfaces based on
> internal representation is a sinful malpractice. More importantly, I see
> no advantage from doing it - it only makes the option parsing more
> complicated.

It's not based on ffmpeg's 'internal representation'. All transform 
attributes are stored as a composite in one mathematical object.
Evaluating the matrix values will need to look at all sources of 
contribution. So gathering and presenting all these attributes in a single
option (+ docs) makes it clearer to the user at the cost of an initial 
learning curve.

Regards,
Gyan

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