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128Kbps channel on VOIP?

 
 
MM
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      10-23-2003
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
>>
>>UDP is not lossy. G.711, like the MP3 audio format, takes an audio
>>stream and creates an approximation of that stream that requires less
>>bandwidth to store or transmit. Once this process is done, it can't be
>>undone. That is, there is no way of recreating the original audio stream.

>
>
> Note quite like MP3, where it uses a lossy compression method. The
> G.711 codec doesn't compress or alter the 'digitized' data. The loss
> actually occurs when you sample the analog data stream (8bit, 8kHz
> typically for voice).
>


So it's strictly quantization error. I know nothing of G.711 (and
little about VoIP for that matter). I was guessing.

MM

 
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root/administrator
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      10-23-2003
(E-Mail Removed) wrote:

> On Tue, 21 Oct 2003 23:24:31 GMT, MM <(E-Mail Removed)> wrote:
>
>>Neil Smith wrote:
>>> On Mon, 20 Oct 2003 19:26:31 GMT, root
>>> <(E-Mail Removed),administrator@localhost> wrote:
>>>
>>>>I thought that's what UDP is all about -- to transfer data over IP.
>>>
>>> Isn't UDP potentially lossy as well ? Better stick to TCP for fax
>>> data or you might lose that important signature ! BTW do www.tpc.com
>>> still do email to fax services ? Might be worth a try for low volume
>>> fax data.

>>
>>UDP is not lossy. G.711, like the MP3 audio format, takes an audio
>>stream and creates an approximation of that stream that requires less
>>bandwidth to store or transmit. Once this process is done, it can't be
>>undone. That is, there is no way of recreating the original audio stream.

>
> Note quite like MP3, where it uses a lossy compression method. The
> G.711 codec doesn't compress or alter the 'digitized' data. The loss
> actually occurs when you sample the analog data stream (8bit, 8kHz
> typically for voice).
>


Any A/D (Analog->Digital) conversion is lossy regardless how high the signal
is sampled.

>
>>UDP does not alter the data passed to it by an application. It differs
>>from TCP in that TCP sequences the data and requires acknowledgement of
>>receipt of that data. If a piece of data is lost, the TCP protocol will
>>detect this and request that the data be retransmitted, completely
>>transparent to the application. The cost of doing this is larger
>>packets due to overhead, plus more traffic due to the acknowledgements.
>> UDP just ships out the data without sequencing or acknowledgements.
>>It is up to the application to detect and retransmit data. If an
>>application that uses UDP loses data, it's the fault of the application,
>>not the tranport protocol.

>
> Also, it's kinda pointless to use TCP for realtime data because if a
> packet isn't delivered on time, you can't use it. The Cisco fax relay
> protocol still doesn't use TCP, but rather sends the same packets
> twice to provide redundancy.
>
> -Chris


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chris@nospam.com
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      10-24-2003


>Any A/D (Analog->Digital) conversion is lossy regardless how high the signal
>is sampled.


Depends entirely on the frequency content of the signal, and whether
you're sampling at a fast enough rate (nyquist rate). Trust me, I
work in the acoustics field.

-Chris


 
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root/administrator
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      10-24-2003
(E-Mail Removed) wrote:

>
>
>>Any A/D (Analog->Digital) conversion is lossy regardless how high the
>>signal is sampled.

>
> Depends entirely on the frequency content of the signal, and whether
> you're sampling at a fast enough rate (nyquist rate). Trust me, I
> work in the acoustics field.
>
> -Chris


Regardless what your nyquist rate is and your work in the acoustics field,
the sampling is always an approximation and therefore it is lossy.

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Miguel Cruz
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      10-24-2003
root/administrator <(E-Mail Removed)> wrote:
> (E-Mail Removed) wrote:
>>> Any A/D (Analog->Digital) conversion is lossy regardless how high the
>>> signal is sampled.

>>
>> Depends entirely on the frequency content of the signal, and whether
>> you're sampling at a fast enough rate (nyquist rate). Trust me, I
>> work in the acoustics field.

>
> Regardless what your nyquist rate is and your work in the acoustics field,
> the sampling is always an approximation and therefore it is lossy.


I think his point is that if, at the end of the day, you are trying to carry
digital data (which is after all the point of this thread) then you can go
to analog and back without necessarily losing data.

Given a sufficient sampling rate, the information that does get lost in the
A/D process was incidentally added as a side effect of the earlier D/A
process and is therefore spurious.

A simple proof of this is the fact that modems work.

miguel
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root/administrator
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      10-24-2003
Miguel Cruz wrote:

> root/administrator <(E-Mail Removed)> wrote:
>> (E-Mail Removed) wrote:
>>>> Any A/D (Analog->Digital) conversion is lossy regardless how high the
>>>> signal is sampled.
>>>
>>> Depends entirely on the frequency content of the signal, and whether
>>> you're sampling at a fast enough rate (nyquist rate). Trust me, I
>>> work in the acoustics field.

>>
>> Regardless what your nyquist rate is and your work in the acoustics
>> field, the sampling is always an approximation and therefore it is lossy.

>
> I think his point is that if, at the end of the day, you are trying to
> carry digital data (which is after all the point of this thread) then you
> can go to analog and back without necessarily losing data.
>
> Given a sufficient sampling rate, the information that does get lost in
> the A/D process was incidentally added as a side effect of the earlier D/A
> process and is therefore spurious.
>
> A simple proof of this is the fact that modems work.
>
> miguel


Modem works mainly because the origin is already a discrete data then it
gets converted to analog (D/A) -> stream through a media between two or
more points -> A/D (back to discrete data at the destination point). The
discrete data that gets converted to an analog form is only as an
approxination and will never (not almost) be faithfully identical to its
analog origination. Thus, it is a lossy conversion.

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Miguel Cruz
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      10-24-2003
root/administrator <(E-Mail Removed)> wrote:
> Miguel Cruz wrote:
>> root/administrator <(E-Mail Removed)> wrote:
>>> (E-Mail Removed) wrote:
>>>>> Any A/D (Analog->Digital) conversion is lossy regardless how high the
>>>>> signal is sampled.
>>>>
>>>> Depends entirely on the frequency content of the signal, and whether
>>>> you're sampling at a fast enough rate (nyquist rate). Trust me, I
>>>> work in the acoustics field.
>>>
>>> Regardless what your nyquist rate is and your work in the acoustics
>>> field, the sampling is always an approximation and therefore it is lossy.

>>
>> I think his point is that if, at the end of the day, you are trying to
>> carry digital data (which is after all the point of this thread) then you
>> can go to analog and back without necessarily losing data.
>>
>> Given a sufficient sampling rate, the information that does get lost in
>> the A/D process was incidentally added as a side effect of the earlier D/A
>> process and is therefore spurious.
>>
>> A simple proof of this is the fact that modems work.

>
> Modem works mainly because the origin is already a discrete data then it
> gets converted to analog (D/A) -> stream through a media between two or
> more points -> A/D (back to discrete data at the destination point).


Congratulations, you have successfully paraphrased what I said.

> The discrete data that gets converted to an analog form is only as an
> approxination and will never (not almost) be faithfully identical to its
> analog origination. Thus, it is a lossy conversion.


The OP wants to transmit digital data. It does not have an analog
origination, only intermediate analog representation.

miguel
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root/administrator
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      10-24-2003
Miguel Cruz wrote:

> root/administrator <(E-Mail Removed)> wrote:
>> Miguel Cruz wrote:
>>> root/administrator <(E-Mail Removed)> wrote:
>>>> (E-Mail Removed) wrote:
>>>>>> Any A/D (Analog->Digital) conversion is lossy regardless how high the
>>>>>> signal is sampled.
>>>>>
>>>>> Depends entirely on the frequency content of the signal, and whether
>>>>> you're sampling at a fast enough rate (nyquist rate). Trust me, I
>>>>> work in the acoustics field.
>>>>
>>>> Regardless what your nyquist rate is and your work in the acoustics
>>>> field, the sampling is always an approximation and therefore it is
>>>> lossy.
>>>
>>> I think his point is that if, at the end of the day, you are trying to
>>> carry digital data (which is after all the point of this thread) then
>>> you can go to analog and back without necessarily losing data.
>>>
>>> Given a sufficient sampling rate, the information that does get lost in
>>> the A/D process was incidentally added as a side effect of the earlier
>>> D/A process and is therefore spurious.
>>>
>>> A simple proof of this is the fact that modems work.

>>
>> Modem works mainly because the origin is already a discrete data then it
>> gets converted to analog (D/A) -> stream through a media between two or
>> more points -> A/D (back to discrete data at the destination point).

>
> Congratulations, you have successfully paraphrased what I said.
>


What you did say was the fact modems work and that was necessary as a proof.
What I wrote was to proof what you said does not necessary proof the
matter. So, your congratulation was not appropriate as well as not needed
in this matter and please save it for some other occasions.

>> The discrete data that gets converted to an analog form is only as an
>> approxination and will never (not almost) be faithfully identical to its
>> analog origination. Thus, it is a lossy conversion.

>
> The OP wants to transmit digital data. It does not have an analog
> origination, only intermediate analog representation.
>
> miguel


That I understood clearly. The point I was trying to proof is that any A->D
conversion is lossy that some of you who has experience of being an
engineer working in the field of acoustic claimed A->D conversion is
lossless. Perhaps, that particular individual should refresh himself with
an A->D conversion knowledge.

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Miguel Cruz
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      10-24-2003
root/administrator <(E-Mail Removed)> wrote:
> Miguel Cruz wrote:
>> The OP wants to transmit digital data. It does not have an analog
>> origination, only intermediate analog representation.

>
> That I understood clearly. The point I was trying to proof is that any A->D
> conversion is lossy that some of you who has experience of being an
> engineer working in the field of acoustic claimed A->D conversion is
> lossless. Perhaps, that particular individual should refresh himself with
> an A->D conversion knowledge.


Due to an explicable myopic fixation on a single decontextualized point,
you're "proving" something that is not in dispute. If you like, you can go
on to prove that water is wet or that trees are made of wood.

The only thing that is lost in the A/D conversion the rest of us are talking
about, is the unwanted noise that was introduced by a prior D/A conversion.
There is no net loss.

miguel
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Miguel Cruz
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      10-24-2003
Miguel Cruz <(E-Mail Removed)> wrote:
> Due to an explicable


Sorry, INexplicable.

miguel
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