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mp3 coding

Started by hemanth kumar September 10, 2003
i am working on a Mp3 codec,can anyone tell me how the
bitstream contains 2 granules of data while the MDCT
block reduces the number to half the number of the in
values.
	
Hi,
MDCT do take 36 samples to produce 18 samples (how?, see MDCT 
expression for that!), but the distribution of those 36 samples 
is, 18 samples from current granule and 18 from previous (This is 
done to maintain the continuity across granules and is taken care 
during decoding as well!). Similar thing happens for next granule 
too... So effectively, for each 18 input samples, though 36 
samples are actually input to MDCT module, only 18 MDCT samples 
come out. Therefore, on the whole, the no. of samples in each 
granule does not come down by half.
(I guess that was your concern... rite!)

Peeyush.
	On Wed, 10 Sep 2003 hemanth kumar wrote :
>i am working on a Mp3 codec,can anyone tell me how
the
>bitstream contains 2 granules of data while the MDCT
>block reduces the number to half the number of the in
>values.
>
>
>
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