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question about the algorithm of AMR-WB
Hi,everbody:
  I'm studing document of AMR-WB(G.722.2).I have found that there hasn't the post-processing in decoder. I know the technic of post prosessing which is supposed after reconstructing speech can improve the quality of reconstructed speech .
  In AMR-WB, there just has some process to adaptive codebook , fixed codebook and gains.
  Dose anybody can help me about why AMR-WB needn't post-processing ?

  • QuantumKnot
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question about the algorithm of AMR-WB
Reply #1
It's quite possible that they didn't put post-processing into AMR-WB standard.  I don't have the technical specs with me at the moment so I'll check them tomorrow.

question about the algorithm of AMR-WB
Reply #2
amr-wb is mainly used for wireless communication, right? in addition, for wideband.
    I have read some papars, and found that most narrowband communication use post processing, but for wb, they just adjust the gain in CLEP
    Does it have some relation to bandwidth?

  • kwwong
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question about the algorithm of AMR-WB
Reply #3
Quote
I'm studing document of AMR-WB(G.722.2).I have found that there hasn't the post-processing in decoder. I know the technic of post prosessing which is supposed after reconstructing speech can improve the quality of reconstructed speech .


What post processing technic do you mean?

question about the algorithm of AMR-WB
Reply #4
a processing  aims at background noise

  • kwwong
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question about the algorithm of AMR-WB
Reply #5
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a processing  aims at background noise
[a href="index.php?act=findpost&pid=366806"][{POST_SNAPBACK}][/a]

Most probably, you will have no problem in adding additional processing at the decoder.

  • QuantumKnot
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question about the algorithm of AMR-WB
Reply #6
Quote
Quote
I'm studing document of AMR-WB(G.722.2).I have found that there hasn't the post-processing in decoder. I know the technic of post prosessing which is supposed after reconstructing speech can improve the quality of reconstructed speech .


What post processing technic do you mean?
[a href="index.php?act=findpost&pid=366787"][{POST_SNAPBACK}][/a]


Most post-processing in CELP coders involve cascading a long-term and short-term postfilter as well as compensating for gain and reducing spectral tilt.  The short-term postfilter emphasises formant peaks and attenuates spectral valleys between formants, while the long-term postfilter emphasises pitch harmonics.  It makes the reconstructed speech sound better.

As to why they haven't applied it to wideband coding, I'm not too sure.  Perhaps, the existing AMR-WB didn't suffer from the quality problems of narrowband CELP.  (and I seem to have forgotten to look up the tech specs, as promised in my earlier post lol)

  • QuantumKnot
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question about the algorithm of AMR-WB
Reply #7
OK, now browsing the tech specs of AMR-WB decoding.  There is some post-processing in the lower bitrate modes (6.60 and 8.85 kbps) such as anti-sparseness processing, noise enhancement, pitch enhancement, etc.