EVRC
Click on the red underlined text to get to the source
... interleaved/
bundled packet formats for the EVRC-B codec, a new compact bundled
format for the EVRC and EVRC-B codecs ...
... packet formats for the EVRC-B codec, a new compact bundled
format for the EVRC and EVRC-B codecs, as well as discontinuous
transmission (DTX ...
... EVRC-B codec, a new compact bundled
format for the EVRC and EVRC-B codecs, as well as discontinuous
transmission (DTX) support for EVRC ...
... EVRC-B codecs, as well as discontinuous
transmission (DTX) support for EVRC and EVRC-B-encoded speech
transported via RTP ...
... discontinuous
transmission (DTX) support for EVRC and EVRC-B-encoded speech
transported via RTP. Voice over IP ...
... bandwidth dial-up and wireless networks require such EVRC
RTP payload capabilities for efficient use of the bandwidth ...
... Support of EVRC-B Codec ...
... EVRC-B [3] is an extension to EVRC [2] developed in the Third
Generation Partnership Project 2 (3GPP2 ...
... 2] developed in the Third
Generation Partnership Project 2 (3GPP2). EVRC-B [3] compresses each
20 milliseconds of 8000Hz, 16-bit ...
... bit codec frame types: null frames and
erasure frames, similar to EVRC [2]. One significant enhancement in
EVRC-B ...
... EVRC [2]. One significant enhancement in
EVRC-B is the use of 1/4-rate frames that were not used in EVRC.
This provides lower average data rates ...
... 2]. One significant enhancement in
EVRC-B is the use of 1/4-rate frames that were not used in EVRC.
This provides lower average data rates (ADRs ...
... voice quality.
Since speech frames encoded by EVRC-B are different from those
encoded by EVRC, EVRC-B ...
... Since speech frames encoded by EVRC-B are different from those
encoded by EVRC, EVRC-B and EVRC codecs do not interoperate with each
...
... EVRC-B are different from those
encoded by EVRC, EVRC-B and EVRC codecs do not interoperate with each
other. At the initiation of an RTP session ...
... encoded by EVRC, EVRC-B and EVRC codecs do not interoperate with each
other. At the initiation of an RTP session, the RTP sender ...
... receiver need to indicate (e.g., using MIME subtypes that are
separate from those of EVRC) that EVRC-B is to be used for the
ensuing session ...
... MIME subtypes that are
separate from those of EVRC) that EVRC-B is to be used for the
ensuing session.
...
... RTP header. The size of the
ToC varies depending on the number of EVRC frames carried in the
packet [4].
...
... header-free format defined in RFC 3558prop.
This format allows bundling of multiple EVRC or EVRC-B frames without
the addition of extra headers ...
... 3558prop.
This format allows bundling of multiple EVRC or EVRC-B frames without
the addition of extra headers, as would be in the case of the
...
... interleaved/bundled format. However, in order to use this compact
bundled format, only one EVRC/EVRC-B rate (full rate or 1/2 rate) can
be used in the session ...
... interleaved/bundled format. However, in order to use this compact
bundled format, only one EVRC/EVRC-B rate (full rate or 1/2 rate) can
be used in the session. Similar to the header-free ...
...
Information carried in frames of EVRC and EVRC-B codecs varies little
during periods of silence. The transmission of these frames across
...
...
Information carried in frames of EVRC and EVRC-B codecs varies little
during periods of silence. The transmission of these frames across
the radio interface ...
...
The EVRC and EVRC-B codecs, in variable-rate operation mode, send
1/8-rate frames during periods of silence, while in single-rate
...
... EVRC-B Codec ...
...
Three RTP packet formats are supported for the EVRC-B codec: the
interleaved/bundled packet format ...
... header-free packet formats, the operational details and capabilities,
such as ToC, interleaving, and bundling, of EVRC-B, are exactly the
same as those of EVRC, as defined in RFC 3558prop ...
... ToC, interleaving, and bundling, of EVRC-B, are exactly the
same as those of EVRC, as defined in RFC 3558prop [4], except that the
...
... ToC MUST be interpreted according to
the definition of the RATE_REDUC parameter in EVRC-B [3]. The
compact bundled packet format ...
... A packet in the compact bundled format consists of an RTP header,
followed by a sequence of one or more consecutive EVRC/EVRC-B codec
data frames of the same rate, as shown below:
...
... RTP header,
followed by a sequence of one or more consecutive EVRC/EVRC-B codec
data frames of the same rate, as shown below:
...
... +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| |
| One or more EVRC/EVRC-B data frames of same rate |
| .... |
...
... | |
| One or more EVRC/EVRC-B data frames of same rate |
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
...
As mentioned earlier, in order to use the compact bundled format, all
the EVRC/EVRC-B data frames in the session MUST be of the same rate.
...
... As mentioned earlier, in order to use the compact bundled format, all
the EVRC/EVRC-B data frames in the session MUST be of the same rate.
This packet format ...
... Storage Format for EVRC-B Codec ...
...
The storage format is used for storing EVRC-B-encoded speech frames,
e.g., as a file or e-mail attachment.
...
... magic number to identify the vocoder that is
used. The magic number for EVRC-B corresponds to the ASCII character
string:
...
... string:
"#!EVRC-B\n"
(or 0x2321 0x4556 0x5243 0x2d42 0x0a in hexadecimal).
...
... Note that the "\n" is an important part of both this magic number and
the "#!EVRC\n" magic number defined in Section 11 of RFC 3558prop, and
...
... magic number,
since, otherwise, a prefix of the EVRC-B magic number could be
mistaken for the EVRC ...
... signaled, the default maxptime value MUST be 200 milliseconds.
fixedrate: Indicates the EVRC rate of the session while in
single-rate operation. Valid ...
... binary data (see RFC 4288, Section 4.8)
and is defined for transfer of EVRC-encoded data via RTP, using
the compact bundled format as described in RFC 4788prop ...
... binary data (see RFC 4288, Section 4.8)
and is defined for transfer of EVRC-B-encoded data via RTP using
the Interleaved ...
... binary data (see RFC 4288, Section 4.8)
and is defined for transfer of EVRC-B-encoded data via RTP using
the Header-Free packet format ...
... signaled, the default maxptime value MUST be 200 milliseconds.
fixedrate: Indicates the EVRC-B rate of the session while in
single-rate operation. Valid ...
... binary data (see RFC 4288, Section 4.8)
and is defined for transfer of EVRC-B-encoded data via RTP using
the compact bundled format as described in RFC 4788prop ...
...
Subtype names: EVRC
Required parameters: none
...
... binary data (see RFC 4288, Section 4.8),
and is defined for transfer of EVRC-encoded data via RTP using the
Interleaved ...
... DTX behavior of DTX-capable EVRC codecs (as detailed in [8],
Section 4.3.5) ensures interoperability ...
... 8],
Section 4.3.5) ensures interoperability with non-DTX EVRC codecs.
Published specification:
...
... binary data (see RFC 4288, Section 4.8)
and is only defined for transfer of EVRC-encoded data via RTP
using the Header-Free packet format ...
... DTX behavior of DTX-capable EVRC codecs (as detailed in [8],
Section 4.3.5) ensures interoperability ...
... 8],
Section 4.3.5) ensures interoperability with non-DTX EVRC codecs.
Published specification:
...
... used to specify sessions employing the compact bundled format for
EVRC/EVRC-B-encoded speech, the mapping is as follows:
...
... sessions employing the compact bundled format for
EVRC/EVRC-B-encoded speech, the mapping is as follows:
o The MIME type ...
...
o The optional parameters "ptime" and "maxptime" (for subtypes EVRC,
EVRC1, EVRCB, and EVRCB1) go in the SDP ...
... audio 49120 RTP/AVP 97
a=rtpmap:97 EVRC/8000
a=fmtp:97 silencesupp=1 dtxmax=32 dtxmin=12 hangover=1
...
... a=fmtp:97 silencesupp=1 dtxmax=32 dtxmin=12 hangover=1
Example of usage of EVRC with DTX with silencesupp=0:
...
... EVRC
payload subtypes "EVRC" and "EVRC0" defined in RFC 3558prop. Since the
new DTX parameters ...
... adaptive DTX behavior of DTX-capable EVRC codecs (as detailed in [8],
Section 4.3.5) ensures the backward interoperability ...
... EVRCB0",
and "EVRCB1" - are defined in this document (see Section 6.1 -
Section 6.4) for EVRC-B and compact bundled payload format support.
...
... payload format support.
For all the EVRC and EVRC-B RTP payload formats defined in RFC 3558prop ...
... Li, A., "RTP Payload Format for Enhanced Variable Rate Codecs (EVRC) and Selectable Mode Vocoders (SMV)", RFC 3558prop, July 2003. ...