Subject: [Cellar] Codec specs: graphical Digital Video Broadcasting (DVB) subtitles

From: Moritz Bunkus <[email-masked]>
Date: Sat, 31 Dec 2016 18:35:25 +0100

Hey,

The Digital Video Broadcasting standard specifies a graphical subtitle
format. There are several programs that have been able to write Matroska
files with such tracks for years. mkvmerge has only gained support for
it after release 9.7.1. On the demuxer side ffmpeg and MPC-HC are
examples of applications that can read and display such S_DVBSUB tracks.

Until now the Matroska codec specs have not reflected this
practice. I've just posted a pull request[1] to remedy the situation. It
describes what is already practice. Nevertheless I ask for reviews. My
recommendation is not adopt the current practice as the official storage
format.

Happy new year, everyone!

Kind regards,
mosu

[1]  https://github.com/Matroska-Org/matroska-specification/pull/77

---

From: Dave Rice <[email-masked]>
Date: Sat, 31 Dec 2016 13:31:27 -0500

> On Dec 31, 2016, at 12:35 PM, Moritz Bunkus <[email-masked]> wrote:
> 
> Hey,
> 

I added some grammar, typo and logic notes within the pull request.

I also see that for many Codecs defined in codec_specs.md, the Description of the Codec contains the requirements for management of private data (within CodecPrivate), but this pull request puts the CodecPrivate details within the subtitles.md document. I suggest the CodecPrivate details get consolidated within codec_specs.md rather than spread out too much in other documents. I also think we should refine the 'Description' of a codec support and split that into a general description and another details value for CodecPrivate handling specifically. Out of scope for this PR, but perhaps we should refine how codec support is defined in more detail soon.

Best Regards,
Dave Rice

---

From: Moritz Bunkus <[email-masked]>
Date: Sat, 31 Dec 2016 19:35:36 +0100

Hey,

> I added some grammar, typo and logic notes within the pull request.

Thanks!

> I also see that for many Codecs defined in codec_specs.md, the
> Description of the Codec contains the requirements for management of
> private data (within CodecPrivate), but this pull request puts the
> CodecPrivate details within the subtitles.md document. I suggest the
> CodecPrivate details get consolidated within codec_specs.md rather
> than spread out too much in other documents. I also think we should
> refine the 'Description' of a codec support and split that into a
> general description and another details value for CodecPrivate
> handling specifically. Out of scope for this PR, but perhaps we should
> refine how codec support is defined in more detail soon.

I agree with that. The first half of the codec_specs.md document could
also use a good rework — both regarding its structure as well as its
content. It's most obvious when you view the rendered page in Jekyll.

But as you said, that's a topic for another PR.

Kind regards,
mosu