Re: [FFmpeg-devel] [PATCH 02/18] fftools/ffmpeg_filter: refactor setting input timebase

From: Tobias Rapp <t.rapp@noa-archive.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 02/18] fftools/ffmpeg_filter: refactor setting input timebase
Date: Mon, 11 Mar 2024 11:12:38 +0100
Message-ID: <8e8947e3-b54b-4ce7-864a-13ccf4c4bfd3@noa-archive.com> (raw)
In-Reply-To: <171011095238.7287.16406128798977096207@lain.khirnov.net>

On 10/03/2024 23:49, Anton Khirnov wrote:

> Quoting James Almer (2024-03-10 23:29:27)
>> On 3/10/2024 7:24 PM, Anton Khirnov wrote:
>>> Quoting Michael Niedermayer (2024-03-10 20:21:47)
>>>> On Sun, Mar 10, 2024 at 07:13:18AM +0100, Anton Khirnov wrote:
>>>>> Quoting Michael Niedermayer (2024-03-10 04:36:29)
>>>>>> why not automatically choose a supported timebase ?
>>>>>> "[mpeg4 @ 0x55973c869f00] timebase 1/1000000 not supported by MPEG 4 standard, the maximum admitted value for the timebase denominator is 65535"
>>>>> Because I don't want ffmpeg CLI to have codec-specific code for a codec
>>>>> that's been obsolete for 15+ years. One could also potentially do it
>>>>> inside the encoder itself, but it is nontrivial since the computations
>>>>> are spread across a number of places in mpeg4videoenc.c and
>>>>> mpegvideo_enc.c. And again, it seems like a waste of time - there is no
>>>>> reason to encode mpeg4 today.
>>>> This is not mpeg4 specific, its just a new additional case that fails
>>> The case you reported is mpeg4 specific.
>>>
>>>> ./ffmpeg -i mm-small.mpg test.dv
>>>> [dvvideo @ 0x7f868800f100] Found no DV profile for 80x60 yuv420p video. Valid DV profiles are:
>>> There is no mechanism for an encoder to export supported time bases.
>> Could it be added as an extension to AVProfile, or AVCodec?
> The two cases are actually pretty different:
> * mpeg4 has a constraint on the range of timebases, and actually does
>    some perverted computations with the timestamps
> * DV just needs your video to be CFR, with a list of supported
>    framerates; dvenc should probably read AVCodecContext.framerate
>    instead of time_base
>
> But most importantly, is there an actual current use case for either of
> those encoders? They have both been obsolete for close to two decades.
> It seems silly to add new API that won't actually be useful to anyone.

Hardware doesn't get outdated as quickly as software. And there are 
people that do not switch their full environment to a new codec every 
decade just to be "in line".

Regards, Tobias
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