Re: [Cellar] Matroska support for closed captions?

Dave Rice <dave@dericed.com> Mon, 27 April 2020 15:46 UTC

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From: Dave Rice <dave@dericed.com>
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Date: Mon, 27 Apr 2020 11:46:32 -0400
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To: Scott Shepherd <sbshepherd=40ChurchofJesusChrist.org@dmarc.ietf.org>
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Subject: Re: [Cellar] Matroska support for closed captions?
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Hi Scott,

> On Apr 22, 2020, at 9:48 AM, Scott Shepherd <sbshepherd=40ChurchofJesusChrist.org@dmarc.ietf.org> wrote:
> 
> Hi all,
>  
> Are there any plans to expand Matroska capability to contain additional stream types such as timecode and closed captions?

Feel welcome to open a ticket at https://github.com/cellar-wg/matroska-specification/issues/new.

> We have some .MXF files (mostly JPEG2000) and are toying with the idea of migrating them to FFV1/.MKV, but currently .MKV can't contain timecode or closed caption streams. While I can’t say I fully understand the need for multiple timecode streams (often there are 3 streams in the .MXF), we’d definitely be losing data where closed captions exist.
>  
> I know that .MKV can hold "attachments," but attachments don't seem like the right solution here. I also know .MKV can hold subtitles, but what we’re seeing in these .MXF files is EIA-608 and EIA-708 closed captions that fail to carry over to .MKV. 

For EIA-608 and EIA-708 data I suppose, either a new type of Codec Mapping could be written (and then these would be a new type of subtitle track) or they could be support as side-data with a BlockAdditionalMapping as described at https://www.ietf.org/id/draft-ietf-cellar-codec-04.html#name-block-additional-mapping. I’m unsure which technique the community would recommend but curious for some discussion on it.

[…]

Best Regards,
Dave Rice