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Technical discussions related to Speech Coding (all itu and other vocoders, ACELP, CELP, AMR, etc)
8 bits samples G.729 - T - Mar 20 16:16:00 2003
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Hi list,
I'm involved in integrating G.729 algorithm.
I know that G.729 encodes with 16 bits samples but our system provides 8
bits input, so
I've allocated these 8 bits samples in the LSB bytes of the 16 bits words before encoding. But sound after encoding/decoding process is so poor. ¿Is there a better way to encode with 8 bits samples?
¿Is it possible to modify the ITU's reference code to do this? Thanks in advance
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Re: 8 bits samples G.729 - Mark Lakata - Mar 20 17:57:00 2003
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Use the MSB byte, not the LSB. You might have to change from unsigned to signed first. Mark Lakata, Staff Engineer 1225 Charleston Road voice 650-567-5170 MIPS Technologies Mountain View CA 94043 fax 650-567-5002 On Thu, 20 Mar 2003, T wrote: > Hi list, > > I'm involved in integrating G.729 algorithm. > > I know that G.729 encodes with 16 bits samples but our system provides 8 bits input, so > I've allocated these 8 bits samples in the LSB bytes of the 16 bits words before encoding. > But sound after encoding/decoding process is so poor. > > ¿Is there a better way to encode with 8 bits samples? > ¿Is it possible to modify the ITU's reference code to do this? > > Thanks in advance |
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Re: 8 bits samples G.729 - Jeff Brower - Mar 20 19:39:00 2003
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T- Is your 8-bit data PCM or A-Law? If PCM, shift to ms byte, watch out for sign bit (may have to subtract 128). If A-Law, convert to 16-bit PCM first. Jeff Brower DSP sw/hw engineer Signalogic > T wrote: > > Hi list, > > I'm involved in integrating G.729 algorithm. > > I know that G.729 encodes with 16 bits samples but our system provides 8 bits > input, so > I've allocated these 8 bits samples in the LSB bytes of the 16 bits words before > encoding. > But sound after encoding/decoding process is so poor. > > ¿Is there a better way to encode with 8 bits samples? > ¿Is it possible to modify the ITU's reference code to do this? > > Thanks in advance |
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Re: 8 bits samples G.729 - Author Unknown - Mar 20 21:02:00 2003
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Surely it will be better to use the bytes as the MSB. Also, I wonder whether your 8 bits are linear or have been companded with A law or mu law? If they are companded, it would be much better to convert them to linear first before doing the 729 encoding. Chuck Hutton In a message dated 3/20/2003 1:16:23 PM Eastern Standard Time, writes: > Hi list, > > I'm involved in integrating G.729 algorithm. > > I know that G.729 encodes with 16 bits samples but our system provides 8 bits input, so > I've allocated these 8 bits samples in the LSB bytes of the 16 bits words before encoding. > But sound after encoding/decoding process is so poor. > > ¿Is there a better way to encode with 8 bits samples? > ¿Is it possible to modify the ITU's reference code to do this? > > Thanks in advance > > Yahoo! Groups Sponsor > ADVERTISEMENT > > > _____________________________________ > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of > Service. |
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Re: 8 bits samples G.729 - Bhanu prakash - Mar 21 14:35:00 2003
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Hi Mark, Is it not sufficient if we put the data in LSB Byte and then "sign extend"?. I think only the signal strength could be less. But, as such there should not be any problem with the quality. Right? David, Do you mean to say that the Quality of sound is poor or Just the strength??? I think, in your case, as sign extension was not done, it treats the values as positive only and hence Quality of should really be poor. Best Regards, Bhanu Prakash. --- Mark Lakata <> wrote: > Use the MSB byte, not the LSB. You might have to > change from unsigned to > signed first. > > Mark Lakata, Staff Engineer 1225 Charleston Road > voice 650-567-5170 > MIPS Technologies Mountain View CA > 94043 fax 650-567-5002 > > On Thu, 20 Mar 2003, T wrote: > > > Hi list, > > > > I'm involved in integrating G.729 algorithm. > > > > I know that G.729 encodes with 16 bits samples but > our system provides 8 bits input, so > > I've allocated these 8 bits samples in the LSB > bytes of the 16 bits words before encoding. > > But sound after encoding/decoding process is so > poor. > > > > ¿Is there a better way to encode with 8 bits > samples? > > ¿Is it possible to modify the ITU's reference code > to do this? > > > > Thanks in advance > __________________________________________________ |
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Re: 8 bits samples G.729 - Mark Lakata - Mar 21 17:56:00 2003
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Remember that G.729 compresses 16 bits to 1 bit, on average. You want to
have your signal in the highest possible bits to be noticed, otherwise it might not be substantially different than background noise. By not shifting 8 bits to the right, that is the equivalent of 48 dB of attenuation, which I would guess is probably not far from the limit of the dynamic range of G.729. Mark Lakata, Staff Engineer 1225 Charleston Road voice 650-567-5170 MIPS Technologies Mountain View CA 94043 fax 650-567-5002 On Fri, 21 Mar 2003, Bhanu prakash wrote: > Hi Mark, > > Is it not sufficient if we put the data in LSB Byte > and then "sign extend"?. I think only the signal > strength could be less. But, as such there should not > be any problem with the quality. Right? > > David, > Do you mean to say that the Quality of sound is poor > or Just the strength??? I think, in your case, as sign > extension was not done, it treats the values as > positive only and hence Quality of should really be > poor. > > Best Regards, > Bhanu Prakash. > > > --- Mark Lakata <> wrote: > > Use the MSB byte, not the LSB. You might have to > > change from unsigned to > > signed first. > > > > Mark Lakata, Staff Engineer 1225 Charleston Road > > voice 650-567-5170 > > MIPS Technologies Mountain View CA > > 94043 fax 650-567-5002 > > > > On Thu, 20 Mar 2003, T wrote: > > > > > Hi list, > > > > > > I'm involved in integrating G.729 algorithm. > > > > > > I know that G.729 encodes with 16 bits samples but > > our system provides 8 bits input, so > > > I've allocated these 8 bits samples in the LSB > > bytes of the 16 bits words before encoding. > > > But sound after encoding/decoding process is so > > poor. > > > > > > ¿Is there a better way to encode with 8 bits > > samples? > > > ¿Is it possible to modify the ITU's reference code > > to do this? > > > > > > Thanks in advance > > > > > > > > > __________________________________________________ |
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