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question about the algorithm of AMR-WB
hengheng1981
post Feb 22 2006, 06:32
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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 ?
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QuantumKnot
post Feb 23 2006, 11:08
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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.
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hengheng1981
post Feb 24 2006, 04:04
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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?
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kwwong
post Feb 24 2006, 04:42
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QUOTE (hengheng1981 @ Feb 21 2006, 11:32 PM)
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? unsure.gif
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hengheng1981
post Feb 24 2006, 07:04
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a processing aims at background noise
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kwwong
post Feb 26 2006, 04:46
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QUOTE (hengheng1981 @ Feb 24 2006, 12:04 AM)
a processing  aims at background noise
*

Most probably, you will have no problem in adding additional processing at the decoder.
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QuantumKnot
post Mar 1 2006, 00:12
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QUOTE (kwwong @ Feb 24 2006, 01:42 PM)
QUOTE (hengheng1981 @ Feb 21 2006, 11:32 PM)
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? unsure.gif
*



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)
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QuantumKnot
post Mar 2 2006, 01:10
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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.
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