[matroska-general] Re: =[SPAM?]= Re: Dynamic Range Management

Christian HJ Wiesner chris at matroska.org
Mon May 26 09:29:27 CEST 2003


Neat :) !!

Frank Klemm wrote:
> On Sun, May 25, 2003 at 04:31:48PM +0200, Steve Lhomme wrote:
> 
>>>Question
>>>~~~~~~~~
>>>
>>>What do you think about this idea ?
>>>Should this be part of Matroska or part of SV8 ?
>>
>>It depends if it's a codec specific thing, or it can be applied to any 
>>codec. In the latter case, I suggest to put it in Matroska. We already 
>>have ReplayGain informations (album and track). And we can add this to 
>>any audio block "properties" (saved in the BlockGroup, even better in 
>>the TimeSlice).
> The Dynamic Changes are not specific to an audio block.
> A new setting can be choosen after 64, 256, 1024 or 4096 samples and this
> new value is applied smoothly between the two props.
>>The problem is that it would be more convenient for the 
>>decoder to have the value for each "frame" and not just when it changes. 
>>Otherwise when you cut or seek in the file, you will lose that information.
> Known.
>>BTW, I'm thinking about when to apply it on decoding. It should be after 
>>decoding to PCM, 
> Dolby Digital applies it to the MDCT coefficients. Side effect is that so
> the DRC is applied smoothly.
>>so either in the Codec (ie this is codec specific, not 
>>supported by all possible codec in matroska) or hacking the output of 
>>the codec (dirty hack in DirectShow, it may be easier in MPlayer). So a 
>>codec specific system would be easier on the matroska side ;) 
> Known.
>>But that's a feature that could be worth adding. To make all codec equal on this 
>>side :) 
> Known. Guess why I'm asking ...
>>And let the codec really deal with coding data. But I'm not sure 
>>it will be the case on encoding, as only the codec can know how to 
>>manipulate data to make compression better.
> The task is not to compress(1) the signal to make it easier to compress(2),
> but to allow a playback in a noisy enviroment or in the late evening.
> Or to apply a fade in and fade out after encoding of the signal.
>> > Generic forms:
>> >   - up to 32 profiles
>> >   - volume can be changed static and dynamic
>> >   - can be used like DRC and Compression
>> >   - can be used for album replaygain
>> >   - can be used for title replaygain (with additional transition
>> >     between titles, to avoid clicks)
>>Good idea. Even though it will need support in the authoring app (not 
>>muxing app).
> SV8:
> - decoder do it automatically
> - you have a function 
>   - to get number of channels
>   - to select the channel
> - editing/manupulation tools are SV8 related
> MATROSKA:
> - range management is done by the matroska framework
> - usable for all audio file formats
> - editing/manupulation tools are MATROSKA related
> - dynamic range stream can have names ...
> - more fexible I think

You mean we could add DRC to MP3 this way ? I dont understand how this 
could be done at all ? How could we make the MP3 decoders aware of the 
matroska DRC flag ? Note that it will be hard, at least on DirectShow, 
to add another filter *AFTER* the MP3 decoder, to alter the DRC.

Of course, for formats that are aware, like MPC, it would be a breeze ;) ...

Christian


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