I am working on a GSM AMR codec. I have optimized the codec for real time operation on a Blackfin DSP on the 533 evaluation board. I capture the input and play it out. I have put the system in two configurations: (a) No codec, plain loopback of the captured sound on the output speaker. I get good sound. (b) When GSM AMR is involved in the operation, the output has the input but it is subdued heavily in noise. The noise is akin to radio static but very pronounced. The codec has been tested/verified with the standard test vectors and found correct. What can be reason for the same ? Best Regards, Akshay
GSM AMR on blackfin.
Started by ●August 1, 2006
Reply by ●August 1, 20062006-08-01
What about the levels? Do you use the full input range of the AD converter? Best regards, Andre Akshay Mishra wrote:> I am working on a GSM AMR codec. I have optimized the codec for real > time operation on a Blackfin DSP on the 533 evaluation board. I capture > the input and play it out. I have put the system in two configurations: > > (a) No codec, plain loopback of the captured sound on the output > speaker. I get good sound. > (b) When GSM AMR is involved in the operation, the output has the input > but it is subdued heavily in noise. The noise is akin to radio static > but very pronounced. > > The codec has been tested/verified with the standard test vectors and > found correct. > > What can be reason for the same ? > > > Best Regards, > Akshay >-- For emailing me, please exchange abuse by a . l o d w i g
Reply by ●August 1, 20062006-08-01
Yes. I used the full input range. Thanks, Akshay Andre wrote:> What about the levels? Do you use the full input range of the AD converter? > > Best regards, > > Andre > > > Akshay Mishra wrote: > > I am working on a GSM AMR codec. I have optimized the codec for real > > time operation on a Blackfin DSP on the 533 evaluation board. I capture > > the input and play it out. I have put the system in two configurations: > > > > (a) No codec, plain loopback of the captured sound on the output > > speaker. I get good sound. > > (b) When GSM AMR is involved in the operation, the output has the input > > but it is subdued heavily in noise. The noise is akin to radio static > > but very pronounced. > > > > The codec has been tested/verified with the standard test vectors and > > found correct. > > > > What can be reason for the same ? > > > > > > Best Regards, > > Akshay > > > > > -- > > For emailing me, please exchange abuse by > a . l o d w i g
Reply by ●August 1, 20062006-08-01
Akshay Mishra wrote:> Yes. I used the full input range. > > Thanks, > Akshay > Andre wrote: >> What about the levels? Do you use the full input range of the AD converter? >> >> Best regards, >> >> Andre >> >> >> Akshay Mishra wrote: >>> I am working on a GSM AMR codec. I have optimized the codec for real >>> time operation on a Blackfin DSP on the 533 evaluation board. I capture >>> the input and play it out. I have put the system in two configurations: >>> >>> (a) No codec, plain loopback of the captured sound on the output >>> speaker. I get good sound. >>> (b) When GSM AMR is involved in the operation, the output has the input >>> but it is subdued heavily in noise. The noise is akin to radio static >>> but very pronounced. >>> >>> The codec has been tested/verified with the standard test vectors and >>> found correct. >>> >>> What can be reason for the same ? >>> >>> >>> Best Regards, >>> AkshayDo you overload it? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 1, 20062006-08-01
Akshay Mishra wrote:> Yes. I used the full input range. > > Thanks, > Akshay > Andre wrote: > > What about the levels? Do you use the full input range of the AD converter? > > > > Best regards, > > > > Andre > > > > > > Akshay Mishra wrote: > > > I am working on a GSM AMR codec. I have optimized the codec for real > > > time operation on a Blackfin DSP on the 533 evaluation board. I capture > > > the input and play it out. I have put the system in two configurations: > > > > > > (a) No codec, plain loopback of the captured sound on the output > > > speaker. I get good sound. > > > (b) When GSM AMR is involved in the operation, the output has the input > > > but it is subdued heavily in noise. The noise is akin to radio static > > > but very pronounced. > > > > > > The codec has been tested/verified with the standard test vectors and > > > found correct. > > > > > > What can be reason for the same ? > > > > > > > > > Best Regards, > > > Akshay > > > > > > > > > -- > > > > For emailing me, please exchange abuse by > > a . l o d w i gThe problem you state is identical to the result one will get if the data are misaligned. I had precisely this problem a little while ago when an object purporting to provide PCM style long frame sync actually provided short frame sync. Makes sense if you think about it. Misaligned data will blow away your sign bit, which is replaced with some random value. The original signal will now exist on an (unknown) 'DC' offset that is much larger than the signal, with the added feature that the 'DC' offset is in fact jumping positive and negative in a random fashion, giving large signal excursions. That's a definition of noise :) Cheers PeteS