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Subject: Re: MPEG Audio format

Re: MPEG Audio format

From: Alun Thomas <>
Date: Sat, 14 Jan 2006 22:18:10 +1300

Bluechip wrote:
> Pretty much got a proper core written for an Audio file processor now.
> I have another simple question about MPEG Audio files.
> Am I ever likely to encounter an MPEG Audio file which will contain
> AUDIO frames which differ in VERSION, LAYER, SAMPLERATE and/or
> CHANNELS? Eg. Some frames are 48KHz and other frames are 44.1KHz ...or
> some frames in Stereo, some in Joint-Stereo?
> I have been unable to find any documentation which explicitly states
> whether this should or shouldn't be allowed by the MPEG standard, and
> nothing to say explicitly whether any players do or don't support this
> type of change.
> There is no reason why not, the file would have a valid structure - but
> it seems unlikely.
> This is relevant to creating the Xing/Xing or Xing/Info frame for VBRFix.
> Thanks for any help,
> BC

Looking through the setup in Razorlame (a lame frontend for windows)
there is the ability to allow different 'block' sizes between channels,
although this is generally disabled. Another option give the ability to
disable using 'short blocks', suggesting that the default is to allow
them. Having stated this, I'm not too sure exactly what they are
refering to with the term 'blocks'. It may mean the same as frame but I
don't know.
Received on 2006-01-14

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