DTX
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... EVRC and EVRC-B codecs, as well as discontinuous
transmission (DTX) support for EVRC and EVRC-B-encoded speech
...
... Discontinuous Transmission (DTX) ...
... wireless system is expensive, in terms of
capacity; therefore, suppression of these frames is desirable. Such
an operation is called DTX, also known as silence suppression.
In general, when DTX ...
... DTX, also known as silence suppression.
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
...
... The full detail of DTX/silence suppression operation can be found in
DTX [8] as well as in RFC 3551std65 [9 ...
... MIME parameters
(silencesupp, dtxmax, dtxmin, and hangover) for setting up a DTX/
silence suppression session, where "silencesupp" is for indicating
...
... silence suppression session, where "silencesupp" is for indicating
the capability and willingness of using DTX/silence suppression;
"dtxmax" and "dtxmin", for indicating the desired range of DTX ...
... DTX/silence suppression;
"dtxmax" and "dtxmin", for indicating the desired range of DTX update
interval; and "hangover", for indicating the desired number of
...
... 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.
...
... sender of this parameter: a) is capable of
receiving silence-suppressed speech using DTX, AND b) is
capable of and will send out silence-suppressed speech using
DTX ...
... DTX, AND b) is
capable of and will send out silence-suppressed speech using
DTX, unless the other end indicates that it does not want to
receive silence-suppressed speech using DTX.
...
... DTX, unless the other end indicates that it does not want to
receive silence-suppressed speech using DTX.
A value of 0 indicates that the sender ...
... A value of 0 indicates that the sender of this parameter: a)
does NOT want to receive silence-suppressed speech using DTX,
AND b) will NOT send out silence-suppressed speech using DTX.
...
... does NOT want to receive silence-suppressed speech using DTX,
AND b) will NOT send out silence-suppressed speech using DTX.
If this parameter is not present, the default value ...
... signaling or other means that it is incapable of or unwilling
to use silence suppression using DTX, silence suppression using
DTX as specified in this document MUST NOT be used for the
...
... to use silence suppression using DTX, silence suppression using
DTX as specified in this document MUST NOT be used for the
session.
...
...
dtxmax: Permissible values are from 0 to 255. Indicates the
maximum DTX update interval in number of frames. During DTX,
...
... maximum DTX update interval in number of frames. During DTX,
the RTP sender occasionally updates the RTP receiver ...
... use 'dtxmax' to indicate to the RTP sender the maximum interval
(in number of frames) between any two DTX updates it expects to
receive from the RTP sender.
...
...
If this parameter is not present in a session that uses DTX,
the default value 32, as specified in [8 ...
... default value 32, as specified in [8], MUST be assumed.
This parameter MUST be ignored if silence suppression using DTX
is not used for the session.
...
...
Note also that if the RTP receiver elects to detect DTX using
dtxmax, the dtxmax parameter will affect the amount of delay
the RTP receiver ...
... dtxmax, the dtxmax parameter will affect the amount of delay
the RTP receiver sees before detecting DTX in the stream.
...
...
dtxmin: Permissible values are from 0 to 255. Indicates the
minimum DTX update interval in number of frames. The RTP
receiver may use 'dtxmin' to indicate to the RTP sender ...
... RTP
receiver may use 'dtxmin' to indicate to the RTP sender the
minimal interval (in number of frames) between any two DTX
updates it expects to receive from the RTP sender.
...
... specified in [8] MUST be assumed. This parameter MUST be
ignored if silence suppression using DTX is not used for the
session.
...
... number of consecutive silence frames transmitted at the end of
an active speech interval but before the DTX interval begins.
When setting up an RTP session ...
... When setting up an RTP session that uses DTX, an RTP receiver
can use this parameter to signal the number of silence frames
...
... RTP receiver
can use this parameter to signal the number of silence frames
it expects to receive before the beginning of DTX. While
hangover=0 is allowed, it is RECOMMENDED that hangover be set
to 1 or greater since the presence of silence frames at the end
...
... active speech can help the RTP receiver to identify the
beginning of the DTX period.
If this parameter is not present for a session ...
...
If this parameter is not present for a session that uses DTX,
the default value 1, as specified in [8 ...
... default value 1, as specified in [8] MUST be assumed. This
parameter MUST be ignored if silence suppression using DTX is
not used for the session.
...
...
(The definition is from RFC 3558prop, added with the optional DTX
parameters, and updated with the new template specified in [10].)
...
... Interoperability considerations:
The DTX parameters are receiver options. Existing RFC 3558prop
...
... receiver options. Existing RFC 3558prop
implementations will not send any of the DTX parameters in their
SDP and will ignore any DTX parameters ...
... DTX parameters in their
SDP and will ignore any DTX parameters they receive. The adaptive
DTX behavior of DTX-capable ...
... SDP and will ignore any DTX parameters they receive. The adaptive
DTX behavior of DTX-capable EVRC codecs (as detailed in [8 ...
... DTX parameters they receive. The adaptive
DTX behavior of DTX-capable EVRC codecs (as detailed in [8],
...
... 8],
Section 4.3.5) ensures interoperability with non-DTX EVRC codecs.
Published specification:
...
...
(The definition is from RFC 3558prop, added with the optional DTX
parameters, and updated with the new template specified in [10].)
...
... Interoperability considerations:
The DTX parameters are receiver options. Existing RFC 3558prop
...
... receiver options. Existing RFC 3558prop
implementations will not send any of the DTX parameters in their
SDP and will ignore any DTX parameters ...
... DTX parameters in their
SDP and will ignore any DTX parameters they receive. The adaptive
DTX behavior of DTX-capable ...
... SDP and will ignore any DTX parameters they receive. The adaptive
DTX behavior of DTX-capable EVRC codecs (as detailed in [8 ...
... DTX parameters they receive. The adaptive
DTX behavior of DTX-capable EVRC codecs (as detailed in [8],
...
... 8],
Section 4.3.5) ensures interoperability with non-DTX EVRC codecs.
Published specification:
...
... payload format are declarative, and all
reasonable values are expected to be supported. In particular, when
DTX is supported, the RTP sender implementation SHOULD support
hangover, dtxmin, and dtxmax values from 0 to 255. Thus, the
...
...
In addition, the following rules MUST be followed while negotiating
DTX parameters:
1. If any DTX parameter ...
... DTX parameters:
1. If any DTX parameter is not present in either offer and/or
answer, the default value of the DTX parameter ...
... DTX parameter is not present in either offer and/or
answer, the default value of the DTX parameter MUST be assumed.
2. If silencesupp is present and set to 0 in either offer or answer,
...
...
2. If silencesupp is present and set to 0 in either offer or answer,
the values of all received DTX parameters other than silencesupp
SHOULD be ignored.
...
... EVRC" and "EVRC0" defined in RFC 3558prop. Since the
new DTX parameters are receiver options, we expect that the existing
RFC 3558prop ...
... receiver options, we expect that the existing
RFC 3558prop implementations will not send any of the DTX parameters in
their SDP and will ignore any DTX parameters ...
... DTX parameters in
their SDP and will ignore any DTX parameters they receive. The
adaptive DTX behavior of DTX-capable ...
... SDP and will ignore any DTX parameters they receive. The
adaptive DTX behavior of DTX-capable EVRC codecs (as detailed in [8 ...
... DTX parameters they receive. The
adaptive DTX behavior of DTX-capable EVRC codecs (as detailed in [8],
...
... 8],
Section 4.3.5) ensures the backward interoperability between the DTX-
capable EVRC codec and non-DTX EVRC codecs ...
... optional parameters -
"silencesupp", "dtxmax", "dtxmin", and "hangover" - are defined and
used in DTX.
The MIME subtype ...
... in RFC 3558prop [4], are updated with the optional DTX parameters (see
Sections 6.5 and 6.6).
...
... "Discontinuous Transmission (DTX) of Speech in cdma2000 Systems", 3GPP2 C.S0076-0, Version 1.0, December 2005. ...