Subject: [Megaco] automatic gain value

From: Gunter Weiss <[email-masked]>
Date: Thu, 18 Oct 2001 19:14:43 +0200

Hello *,

I have a question concerning gain value in Megaco messages:
For me it is not clear which value is the right one for automatic gain!

Having a more close look to RFC 3015, this is exactly what RFC tells us.
       Unfortunately the sentence in RFC 3015:
       "The gain control parameter may either be specified as "automatic"
         (0xffffffff), or as an explicit number of decibels of gain (any other
         integer value).  The default is provisioned in the MG."

       is missleading !

       The definition says:

          Gain Control
          ------------
          PropertyID: gain (0x000a)

          Gain control, or usage of of signal level adaptation and noise level
          reduction is used to adapt the level of the signal. However, it is
          necessary, for example for modem calls, to turn off this function.

          Type: enumeration (integer)

       Later on page 113 or 114 of RFC the range is explicitly given as:

       Cuervo, et al.              Standards Track                   [Page 113]

       RFC 3015              Megaco Protocol Version 1.0          November 2000

         | Echocanc          | 100B | Enumeration | Echo Canceller: Off(0),   |
         |                   |      |             | G.165(1), G168(2)         |
         +-------------------+------+-------------+---------------------------+
         | Gain              | 100C | Unsigned    | Gain in db: 0-65535       |
         |                   |      | Integer     |                           |
         +-------------------+------+-------------+---------------------------+

       If you ask me, even the value 0xffffffff is wrong in RFC it could be only 0xffff!

Please if someone could help me out of this confusion!

Kind regards,
    Gunter

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---

From: "Chuong N. Nguyen" <[email-masked]>
Date: Mon, 22 Oct 2001 15:36:54 -0500

Terry

Something for the IG.
In one of the IG version, the Type has been corrected to just say integer - no enumeration.

Now going by Standard Section 12.1.2 where

   *  Type: One of:
      String: UTF-8 string
      Integer: 4 byte signed integer

In Annex C.1, Gain is defined as "Unsigned Integer.
So either C.1 or "tdmc" package needs to be changed.

Once it is determined whether it is "Unsigned Integer" or "integer", the text needs to be
updated as
to what the "automatic" value needs to be.

Also a clarification needs to be added to the tmdc package to specify whether the db gain
value
should be presented as hex (0x) or decimal for ABNF.

I think it could be both and it is up to the parser (or the receiver of the msg)
to be able to convert from hex or decimal ASCII representation to binary representation for
internal
computation/manipulation.

For example, the db gain value can be defined as
(hex-prefix hex-U16) / 1*5(DIGIT) or
hex-prefix = "0" ("x"  /  "X")

For example, MGC can send
   tdmc/gain=10
or
  tdmc/gain = 0xa

Any comments?

Thanks
Chuong

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