Re: [Cellar] Adding private elements to Matroska
Tobias Rapp <t.rapp@noa-archive.com> Mon, 16 April 2018 06:58 UTC
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From: Tobias Rapp <t.rapp@noa-archive.com>
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Date: Mon, 16 Apr 2018 08:58:06 +0200
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Subject: Re: [Cellar] Adding private elements to Matroska
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On 15.04.2018 16:24, Jerome Martinez wrote: > On 15/04/2018 15:47, Steve Lhomme wrote: >> 2018-04-15 15:37 GMT+02:00 Jerome Martinez <jerome@mediaarea.net>: >>> [...] >>> Most modern formats have private elements (MPEG-TS has >>> registration_format_identifier in descriptors for knowing what is >>> used for >>> table_id>=0x80, AVC/HEVC uses "user_data_unregistered" in user_data >>> followed by uuid_iso_iec_11578 for uniqueness, MP4/MOV uses "uuid" >>> atom also >>> followed by an UUID...), even AV1 is planning METADATA_TYPE_PRIVATE_DATA >>> metadata type for storing private data, I guess it is not for nothing >>> ;-), >>> so I think that planning nothing for people wanting to store unspecified >>> content is a good method, if we plan that Matroska is even more used >>> that >>> currently, so any company would be interested in storing private >>> content as >>> they do for years when they use a format. >> I think you're comparing to formats that are not easily extensible by >> nature (I might be wrong). > > MP4/MOV has a similar method about element, there are 2^32 possibilities. > But it does not prevent conflicts, as 2 entities may use the same > element name (2^32 possibilities, but people may limit their choice to a > subset of possibilities, e.g. easily readable in English), I guess this > is the reason "uuid" atom appeared later in files. > > >> EBML/Matroska allows private extensions >> without breaking anything. DivX did it, WebM did it. It's just the >> validation/remuxing of files that may cause problems. >> > > Taking the example of DivX, issue is if 2 entities use accidentally the > same element name before seeing that the other has chose the same > element name. > Some months ago when working with AVI/RIFF I had the need to store some "sparse" file data. Basically it was an index file with all the metadata chunks except for the actual media ("data" chunk), plus some custom chunks. There I did choose a "unique" 2-char ASCII prefix for the RIFF identifiers in the hope that it would not collide with any chunks in the input AVI file. When Matroska gets more popular I assume something similar to the AVI indexing above will be implemented for Matroska and I would be in a similar situation to pick some "unique" element identifiers. In my scenario there is no problem regarding validation on output side, as the private elements are ignored when copying elements from the index file into the output file. Regards, Tobias
- [Cellar] Adding private elements to Matroska Jerome Martinez
- Re: [Cellar] Adding private elements to Matroska Tobias Rapp
- Re: [Cellar] Adding private elements to Matroska hubblec4
- Re: [Cellar] Adding private elements to Matroska Michael Bradshaw
- Re: [Cellar] Adding private elements to Matroska Moritz Bunkus
- Re: [Cellar] Adding private elements to Matroska Steve Lhomme
- Re: [Cellar] Adding private elements to Matroska Jerome Martinez
- Re: [Cellar] Adding private elements to Matroska Steve Lhomme
- Re: [Cellar] Adding private elements to Matroska Moritz Bunkus
- Re: [Cellar] Adding private elements to Matroska Steve Lhomme
- Re: [Cellar] Adding private elements to Matroska Jerome Martinez
- Re: [Cellar] Adding private elements to Matroska Jerome Martinez
- Re: [Cellar] Adding private elements to Matroska Tobias Rapp