[Matroska-devel] Re: Profiles v2

Atamido paul at msn.com
Tue Mar 15 05:53:28 CET 2005


Steve Lhomme wrote:
> Zen a écrit :
>> DTS : should be able to handle 6.1 or 7.1 streams. 7.1 audio is the 
>> future of audio, even more in computers (see HDA, Intel High 
>> Definition Audio in relpacement of old AC97)
> 
> The number of supported channels is an indication for the player. 
> Meaning that it should be the minimum to support. Same for the codec 
> list. They will probably all support WMA and WMV9. But we don't had that 
> to our list, simply because we don't support these codecs for the moment.

I would say that this is a bit of a special case.  The player itself 
doesn't need to 'support' a certain number of channels in DD or DTS. 
Basically all DVD players only output the raw encoded data to a digital 
out so that it can be decoded by a receiver.  My receiver supports a lot 
of different forms of DD and DTS, but the only thing my DVD player 
decodes is the different MPEG layer audio, which is always 2 channel.

So a hardware device like a DVD player should be required to support 
outputting DD and DTS of any channel amount to it's digital outs.  I 
don't think decoding should be required at all as it is so rare. (Some 
DVD players include DD decoders and an amp and 6 speaker outputs, but 
they aren't common.)

Other audio formats are harder though.  Vorbis for instance.  If a 
Vorbis file is in 5.1, what should be required?  That it be able to 
decode it and down mix to 2 channel?  That it be able to decode at least 
the front two channels?  AAC is the same situation.  WavPack and FLAC 
are a similar situation, although those are only likely to contain 2 
channel audio.

>> Resolution : specify this is "up to" : what to do of video in 712*572? 
>> Should it be OK with players supporting 720*576? Video should be PAL 
>> (720*576) or NTSC (720*480) with no ratio problems
> 
> I used PAL as an example. Of course it's not a strict limit. And the 
> main pb on resolution is the one for PocketPCs as most of them don't 
> support VGA, maybe even some PMP ones don't. So the choice here (and 
> everywhere else too) is do we want very few but very good profile 
> compliance, or a more relax one that could be used in lots of devices.

You could have a class of "DVD Player" certifications, and a class of 
"PDA" classifications.  Then you could also add an something like a 
"Ultra small" for something like cell phones in the future if it was 
required.

>> Are you sure that TTA, WavPack and Flac are necessary? This is not a 
>> mass usage... a lot less than DTS 6.1!!! Will it be used by Industry? 
>> I think not, Industry think to lossly compression...
> 
> Support for these codec is easy. But it's true that it looks strange 
> that we support 3 lossless codec. Especially since some devices would 
> not be compliant just because of that. Maybe I consider them as too 
> important. If I had to choose one, it would be Wavpack, because it has 
> this hybrid mode, which is good for portable players. So maybe I'll drop 
> the other 2. Having at least one (again, that list in the minimum) is 
> also a choice of quality vs ease of compliance... In the other hand TTA 
> is a CoreCodec project and the format itself is very simple and 
> efficient compared to FLAC. But that would be more a political choice.

Using FLAC may be considered a 'politically friendly' move.  I don't 
really know though.  I do think that FLAC is more commonly used than any 
of the other formats.  So if you wanted to go by what is in most common 
existence, than it would be FLAC.  Of course FLAC in Matroska probably 
isn't as common as other formats in Matroska.  Maybe something like "One 
of these three formats must be supported."  If you did that then players 
would have their option of which to support, whatever is easiest for 
them to implement in hardware.  And theoretically since they would all 
be for lossless, you could easily trans code between them.


Atamido




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