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From: Lynne <dev@lynne.ee>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] libavcodec/mpeg12: Remove "fast" mode
Date: Mon, 30 Oct 2023 02:22:28 +0100 (CET)
Message-ID: <NhyACAD--3-9@lynne.ee> (raw)
In-Reply-To: <a6f29a4b-f1aa-42ee-8fa8-fa406aa0f002@gmail.com>

Oct 30, 2023, 01:02 by leo.izen@gmail.com:

> On 10/29/23 11:48, Lynne wrote:
>
>> Oct 29, 2023, 16:43 by kierank@obe.tv:
>>
>>> $subj as discussed at VDD
>>>
>>> Kieran
>>>
>>
>> This isn't Opus or JPEG-XL, there should be a single correct way of decoding something.
>> Looks good to me.
>> _______________________________________________
>>
>
> I'm not sure I understand what you mean - JPEG XL is fully specified. Are you thinking of mjpeg?
>

Anything that does not have a decoder fully defined with fixed-point math
or at least does not define a specific floating point format, with all constants
being given in that float format unambiguously (e.g. regular IEEE 32-bit floats, with all
constant values being given as 32-bit hex), along with a defined and bitexact
mathematical operations (i.e. IEEE). Giving only float constants up to a reasonable
decimal point and defining a maximum error is just not how video codecs
are defined.

Yeah, compared to Opus, JPEG-XL is really ordinary and shouldn't have been there,
and it can be argued that the error margins are small enough to permit bitexactness
up to a bit depth, but I nevertheless would've liked to see fixed-point specifications.
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  reply	other threads:[~2023-10-30  1:22 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-29 15:43 Kieran Kunhya
2023-10-29 15:48 ` Lynne
2023-10-30  0:02   ` Leo Izen
2023-10-30  1:22     ` Lynne [this message]
2023-10-30  1:29       ` Leo Izen
2023-10-29 21:33 ` Michael Niedermayer
2023-10-30  6:40 ` Matthias Dressel
2023-10-30 10:31   ` Kieran Kunhya

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