[FFmpeg-devel] [RFC] additinal desc_type for dtshd mpeg-ts demuxer

Måns Rullgård mans
Mon Jun 9 10:08:08 CEST 2008

Nico Sabbi <Nicola.Sabbi at poste.it> writes:

> On Monday 09 June 2008 09:48:34 M?ns Rullg?rd wrote:
>> "Ian Caulfield" <ian.caulfield at gmail.com> writes:
>> > 2008/6/9 Andreas ?man <andreas at olebyn.nu>:
>> >> M?ns Rullg?rd wrote:
>> >>> Is it correct to use the same codec id?  Can AC3/DTS decoders
>> >>> in general handle all the variants?  Might an lavf-using app
>> >>> want to distinguish between them?
>> >>
>> >> IEC958 (SPDIF) comes to mind.
>> >> You might want to configure AC3, DTS, etc to be sent directly to
>> >> a AV receiver, but such receiver might not be able to decode DTS
>> >> HD and such, so it is necessary to be able to distinguish
>> >> between the variants.
>> >>
>> >> Ether we could add more codec IDs or use sub_id. Dunno what's
>> >> best though.
>> >
>> > I think DTS is meant to fallback nicely - a decoder that can
>> > handle DTS but not DTS-HD should be able to decode a DTS-HD
>> > stream as just 1.5mbs DTS and ignore the extra data... not sure
>> > if that's true in practice though!
>> However that may be, it still means losing data.  In such a
>> situation I'd want to use a software decoder for DTS-HD streams.
> IMO a different stream type requires a different codec_id/decoder pair

The question is when to call it different stream types, rather than
variants of the same type.  We don't differentiate (much) between MPEG
audio layers, for instance.

M?ns Rullg?rd
mans at mansr.com

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