On 10/24/2012 08:10 AM, Bruce wrote:
>> In the list I got, the VQ (used by the 1200 bps codec) where at the same
>> place of the LSPs for the 1400 bps codec. Would you place them higher?
> My (very imperfect) understanding is that corrupting an LSP is like
> distorting one filter tap while corrupting VQ can effect more than one.
> Also, David noted that the first VQ index is the most sensitive.
Well, corrupting one LSP changes all filter taps, even though the effect
on the spectrum is generally localized. When it comes to VQ, it depends
on what bit you lose. If you lose a bit of the highest stage, the effect
tends to be severe and you're better off considering the frame "lost"
(assuming you can detect the error). For lower stages though, the
distortion shouldn't be too bad. Possibly less than for scalar
quantization. One other aspect that can increase robustness of VQ is
index assignment. The idea is to optimize the ordering of the codebook
to minimize distortion when a bit gets corrupted.
Jean-Marc
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