[FFmpeg-devel] [PATCH]lavf/isom: Recognize fourcc HEVC

James Almer jamrial at gmail.com
Wed May 2 23:30:31 EEST 2018

On 5/2/2018 4:47 PM, Carl Eugen Hoyos wrote:
> 2018-05-02 21:26 GMT+02:00, James Almer <jamrial at gmail.com>:
>> On 5/2/2018 3:59 PM, Carl Eugen Hoyos wrote:
>>> 2018-05-02 20:52 GMT+02:00, James Almer <jamrial at gmail.com>:
>>>> On 5/2/2018 3:44 PM, Carl Eugen Hoyos wrote:
>>>>> Attached patch fixes ticket #7110 for me.
>>>> hevc in AVI is not a thing, and adding a non official fourcc to
>>>> ff_codec_movvideo_tags to support weird files created by
>>>> faulty software that are not even mov/mp4 is not a good idea.
>>> So what do you suggest?
>>> Not supporting files that are written by common software?
>> Asking the source of these files (VirtualDub) to stop creating them is
>> one option. Otherwise we'll be adding a similar tag to support h266 in
>> avi five years from now because people refuse to do things right.
> How does this help?

An attempt to prevent the creation of even more broken non standard crap
in the future.

> We know that several applications write such files and they didn't
> stop it when we asked last time?

So we ask them to stop creating broken files, they ignore us, and the
result is we bend over and litter our codebase with workarounds for the
crap they release into the wild?

> Much more important: We try not to write invalid files, what is
> suddenly bad about trying to support everything out there?
> We support quite a few formats that are most likely less
> common than hevc-in-avi and this was a very successful
> approach afaict.
> Why suddenly tell users to fuck themselves? Why does
> this make sense?

Not to the users. To the developers of these applications if anything.

>> Alternatively, actually start using avfmtctx->strict_std_compliance on
>> demuxers and refuse to handle these files unless it's set as unofficial
>> or lower, but i predict a lot of people will come out of the woodworks
>> complaining about their broken samples suddenly not working anymore
>> because ffmpeg started to honor its own standard compliance settings.
> Sounds completely unacceptable to me.

And that's a problem. We add options to let the user choose between
supporting non standard features or not, then make it do nothing and
instead hardcode things in the laxest mode possible, which includes crap
like this.

If we start actually having some standards about standard compliance and
users start being told that their files are broken, then these
applications might get some incentive to stop creating them to begin with.

>>>> Why the hell is the avi demuxer even looking at mov tags to begin with?
>>> Because every other software except FFmpeg writes such files.
>> I doubt we're the only ones that try to not write non standard files...
> Do you know immediately of another (general-usage!) tool?

Why are you asking me to list other software when you are the one that
assured me everyone but us writes crap like hevc in avi? Is it really
every other program, or just VirutalDub, as the comment you added to
this new ff_codec_movvideo_tags entry implies? What other program does
if it's not just that one?

If it's really that common and every other avi muxing application out
there writes hevc using this specific fourcc tag, then you'll have a
better argument to add support for it.

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