Reply by krishnamurthy vaidyanathan●April 30, 20022002-04-30
Is it possible that a DC offset be added at the
digitizing stage - say unmatched A/D s ?
Poochi
--- Sameer Kibey <> wrote: > Hi all!
>
> as far as the use of high pass filter in
> preprocessing
> is concerned,the reasoning of removal of the 50/60
> Hz
> hum is indeed agreeable.
> another use of the high pass filter could be removal
> of an unnecessary DC offset present in the signal.
> now, my question : is the addition of such a DC
> component in speech posssible? if yes, what is the
> cause/source of this DC offset?
>
> Sameer.
>
> --- Bhanu Prakash <>
> wrote:
> > Hi Subrata,
> > The answers for ur questions are:
> > 1.The high pass filtering in any speech codec is
> to
> > filter out
> > flicker noise(1/f) and also to filter interference
> > of 50/60 hz hum.
> > 2.Signal down scaling is to minimise handling of
> > overflow conditions
> > down the path of processing in case of fixed point
> > operations.
> > This is compensated by signal upscaling at the
> > decoder.
> >
> > I think i have answered your questions.If any one
> > has any other answers
> > i would like to hear.
> >
> > Best Regards,
> > Prakash.
>
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> Hi all!
>
> as far as the use of high pass filter in preprocessing
> is concerned,the reasoning of removal of the 50/60 Hz
> hum is indeed agreeable.
> another use of the high pass filter could be removal
> of an unnecessary DC offset present in the signal.
> now, my question : is the addition of such a DC
> component in speech posssible? if yes, what is the
> cause/source of this DC offset?
Such DC offsets can come from ADC (Analog to Digital Converters).
They are basically analog devices, whose properties might
change depending on various factors.
I have observed many times the digital speech signal
contained some DC values (non zero mean), immediately after the ADC,
which is not good for many of the speech codecs. The problem
can be solved using a very inexpensive high pass filter.
>
>
> Sameer.
>
> --- Bhanu Prakash <> wrote:
> > Hi Subrata,
> > The answers for ur questions are:
> > 1.The high pass filtering in any speech codec is to
> > filter out
> > flicker noise(1/f) and also to filter interference
> > of 50/60 hz hum.
> > 2.Signal down scaling is to minimise handling of
> > overflow conditions
> > down the path of processing in case of fixed point
> > operations.
> > This is compensated by signal upscaling at the
> > decoder.
> >
> > I think i have answered your questions.If any one
> > has any other answers
> > i would like to hear.
> >
> > Best Regards,
> > Prakash.
> >
>
> __________________________________________________
>
> _____________________________________
> Note: If you do a simple "reply" with your email client, only the
author of this message will receive your answer. You need to do a "reply
all" if you want
your answer to be distributed to the entire group. >
> _____________________________________
> About this discussion group:
>
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>
> To Post:
>
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>
> Archives: http://www.yahoogroups.com/group/speechcoding
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Reply by Sameer Kibey●April 27, 20022002-04-27
Hi all!
as far as the use of high pass filter in preprocessing
is concerned,the reasoning of removal of the 50/60 Hz
hum is indeed agreeable.
another use of the high pass filter could be removal
of an unnecessary DC offset present in the signal.
now, my question : is the addition of such a DC
component in speech posssible? if yes, what is the
cause/source of this DC offset?
Sameer.
--- Bhanu Prakash <> wrote: > Hi Subrata,
> The answers for ur questions are:
> 1.The high pass filtering in any speech codec is to
> filter out
> flicker noise(1/f) and also to filter interference
> of 50/60 hz hum.
> 2.Signal down scaling is to minimise handling of
> overflow conditions
> down the path of processing in case of fixed point
> operations.
> This is compensated by signal upscaling at the
> decoder.
>
> I think i have answered your questions.If any one
> has any other answers
> i would like to hear.
>
> Best Regards,
> Prakash.
>
1.The high pass filtering in any speech codec is to filter out flicker
noise(1/f) and also to filter interference of 50/60 hz hum.
2.Signal down scaling is to minimise handling of overflow conditions down the path of processing in case of fixed point operations. This is
compensated by signal upscaling at the decoder.
I think i have answered your questions.If any one has any other
answers i would like to hear.
Best Regards, Prakash.
-------Original Message-------
From: s...@yahoo.co.in
Date: Thursday, April 25, 2002 11:39:23 PM
To: s...@yahoogroups.com
Subject: [speechcoding] Why high pass filtering and
down scaling in pre processing
hi friends, In AMR speech codec why do we need to use high
pass filtering and down scaling in pre processing??? Again the
technique of down scalling is not clear to me....So please anyone help me
by answering the above queries in detail.
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Reply by subrata chatterjee●April 25, 20022002-04-25
hi friends,
In AMR speech codec why do we need to use high pass
filtering and down scaling in pre processing???
Again the technique of down scalling is not clear to
me....So please anyone help me by answering the above
queries in detail.