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What's the meaning of "sample rate" in MP3/Vorbis/AAC?, Considering the audio was transformed
sheh
post Oct 7 2012, 03:44
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What's the meaning of "sample rate" in MP3/Vorbis/AAC? Wouldn't it be meaningless after transform, same as bit depth?
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lvqcl
post Oct 7 2012, 18:56
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Winamp MP3 decoder still have Full/Half/Quarter quality setting
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benski
post Oct 10 2012, 16:16
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QUOTE (lvqcl @ Oct 7 2012, 13:56) *
Winamp MP3 decoder still have Full/Half/Quarter quality setting


Yes, and it does this by not doing the calculations for all the bands, and only doing a 16 or 8pt iMDCT at the end. Remember that MP3 is cascade of 32 18-pt iMDCTs followed by a 32-pt iMDCT. This was done mainly to reuse hardware and software from Layer 2 decoders. From memory, I think there's a step in between that would prevent an implementation from simply using a 576 point MDCT.

This post has been edited by benski: Oct 10 2012, 16:21
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- sheh   What's the meaning of "sample rate" in MP3/Vorbis/AAC?   Oct 7 2012, 03:44
- - saratoga   No, the transform occurs on sampled data and so th...   Oct 7 2012, 05:05
|- - sheh   I guess the way I put it does seem like a retread....   Oct 9 2012, 05:21
|- - saratoga   QUOTE (sheh @ Oct 9 2012, 00:21) Benski s...   Oct 9 2012, 19:03
- - pdq   Still. since the data are stored as frequencies an...   Oct 7 2012, 14:23
- - [JAZ]   When we say that lossy streams don't have a st...   Oct 7 2012, 14:44
- - jensend   I'm not intimately acquainted with the details...   Oct 7 2012, 16:46
- - benski   fs is part of the MDCT equation. If you didn...   Oct 7 2012, 18:32
|- - sheh   Okay, so the original fs needs to be plugged in so...   Oct 8 2012, 18:33
- - lvqcl   Winamp MP3 decoder still have Full/Half/Quarter qu...   Oct 7 2012, 18:56
|- - benski   QUOTE (lvqcl @ Oct 7 2012, 13:56) Winamp ...   Oct 10 2012, 16:16
- - saratoga   Using a dct means you could easily drop the sample...   Oct 7 2012, 19:00
|- - saratoga   QUOTE (sheh @ Oct 8 2012, 13:33) Okay, so...   Oct 8 2012, 23:41
- - jensend   I still think you're wrong here. Once you...   Oct 7 2012, 19:57
|- - saratoga   QUOTE (jensend @ Oct 7 2012, 14:57) I sti...   Oct 7 2012, 20:16
- - Dynamic   I think one problem is that we're never doing ...   Oct 8 2012, 23:04
- - [JAZ]   Mmm.. the tranformation that (most) lossy codecs d...   Oct 9 2012, 19:03
|- - Dynamic   QUOTE ([JAZ] @ Oct 9 2012, 19:03)...   Oct 9 2012, 22:22
- - pdq   So am I understanding correctly that 99.9% of deco...   Oct 10 2012, 17:12
|- - saratoga   QUOTE (benski @ Oct 10 2012, 11:16) QUOTE...   Oct 10 2012, 17:30
- - [JAZ]   QUOTE (Dynamic @ Oct 9 2012, 23:22) As [J...   Oct 10 2012, 17:52
|- - saratoga   QUOTE ([JAZ] @ Oct 10 2012, 12:52...   Oct 10 2012, 18:20
- - [JAZ]   Winamp with the in-house decoder (i.e. not the fra...   Oct 10 2012, 18:41
|- - saratoga   QUOTE ([JAZ] @ Oct 10 2012, 13:41...   Oct 10 2012, 18:55
- - Dynamic   My recollection is that Winamp 1.7 running under W...   Oct 11 2012, 16:14
- - sheh   So sample rate matters. I suppose without being fa...   Oct 11 2012, 23:20

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