Subject: [AVT] EVRC RFC 4788 question

From: "Yuval Nissan" <[email-masked]>
Date: Wed, 16 May 2007 13:03:08 +0300

Hi,

I have question regarding using silence compression in fixed rate mode.

>From RFC 4788:

"The EVRC and EVRC-B codecs, in variable-rate operation mode, send
   1/8-rate frames during periods of silence, while in single-rate
   operation mode (see Section 4), silence is encoded and sent in frames
   of the same rate as that of speech frames.  The DTX parameters
   defined in this document apply to 1/8-rate frames in the variable-
   rate mode and to silence frames in the single-rate operation mode."

If silence is encoded (in fixed rate) in the same rate as speech frames
(so there aren't any real gaps in time), why does it needed? 

What is the meaning of dtxmin and dtxmax in this mode?

Please explain.

Regards,

Yuval 

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
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---

From: "Desineni, Harikishan" <[email-masked]>
Date: Wed, 16 May 2007 11:21:09 -0700

Yuval,
 
There can be periods at which there would be no frame transmission even
in fixed rate operation mode. I would like to point to the following
text from section 1.3.  The procedures in this section are applicable to
1/8th rate frames in variable rate operation mode and to full rate
frames in fixed rate operation mode (evrcb1). 
 
>From Sec 1.3:
"In general, when DTX/silence suppression is applied, the first few
   frames of silence may be transmitted at the beginning of the period
   of silence to establish background noise.  Then, a portion of the
   stream of subsequent silence frames is not transmitted, and is
   discarded at the sender.  At the receiver, background or comfort
   noise may be generated by using the previously received silence
   frames."

Thanks,

Hari

________________________________

From: Yuval Nissan [mailto:[email-masked]] 
Sent: Wednesday, May 16, 2007 3:03 AM
To: [email-masked]
Subject: [AVT] EVRC RFC 4788 question

Hi,

Please explain.

Regards,

Yuval