Impulse response of short blocks in Wiki article about MP3 |
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Impulse response of short blocks in Wiki article about MP3 |
 Jun 2 2009, 21:50
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#1
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 Group: Members Posts: 3493 Joined: 14-May 03 From: Bad Herrenalb Member No.: 6613  |
Can anyone explain to me how the 18.6ms are calculated in http://wiki.hydrogenaudio.org/index.php?ti...hase_filterbank with regards to the impulse response of the short blocks?
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Jun 2 2009, 22:10
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#2
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 Group: Developer Posts: 822 Joined: 2-December 07 Member No.: 49183 |
Even more funny:
"At 48kHz sampling rate a long block has a time resolution of about x ms." ??? |
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Jun 2 2009, 23:09
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#3
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 Group: Members Posts: 1219 Joined: 20-March 04 From: Göttingen (DE) Member No.: 12875 |
QUOTE (Sebastian Mares @ Jun 2 2009, 21:50)  Can anyone explain to me how the 18.6ms are calculated in http://wiki.hydrogenaudio.org/index.php?ti...hase_filterbank with regards to the impulse response of the short blocks? The bandpass filters of the 32 subband filterbank have a response of 512 samples. The impulse responses of the filters in the MDCT filterbank for short blocks hace an impulse response of 12 but this is at 1/32 of the sampling rate. Now, to get the length of the combined impulse responses: 512 + 32*12 - 1 = 895 samples. At 48000 Hz this corresponds to 18.646 ms. OTOH most of samples (probably the beginning and ending 5 ms -- I havn't checked) are close to zero. So, it's actually not that big a deal. Cheers! SG |
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Lo-Fi Version | Time is now: 22nd November 2009 - 03:25 |
