1. ACLI Configuration Guide
  2. Transcoding
  3. EVRC Family of Codecs

EVRC Family of Codecs

The Acme Packet 6300 supports 2 codecs in the EVRC family. Each codec has has three variants.

  • EVRC-A is also commonly referred to as EVRC. The following EVRC-A packet formats are supported:

Header-free packet format = EVRC0

Bundled/interleaved packet format = EVRC

Compact Bundled packet format = EVRC1

  • The following EVRC-B packet formats are supported:

Header-free packet format = EVRCB0

Bundled/interleaved packet format = EVRCB

Compact Bundled packet format = EVRCB1

EVRC-A Codec for Transcoding

The Acme Packet 6300 supports the Enhanced Variable Rate codec (EVRC) for transcoding. Three subtypes of the EVRC codec are supported as media-profiles:

  • EVRC0—header-free EVRC format. This codec is transcodable.
  • EVRC—non-header-free EVRC format. This codec is transcodable.
  • EVRC1—fixed rate EVRC format. This codec is transcodable.

Note:

The Acme Packet 6300 handles optional parameters according to RFC 4788 unless otherwise specified.

EVRC0 Supported Options

Required Parameters: none

Optional Parameters:

  • silencesupp—If this parameter is not present in a DTX session, the default value 1 MUST be assumed.
  • dtxmax—If this parameter is not present in a DTX session, the default value is 32.
  • dtxmin—If this parameter is not present in a DTX session, the default value is 12.
  • hangover—If this parameter is not present in a DTX session, the default value 1 MUST be assumed.

The payload type is dynamic for this codec. EVRC0 specifies the header-free format of the EVRC codec. Only a single frame (20 ms) is allowed in header-free mode.

EVRC Supported Options

Required Parameters: none

Optional parameters:

  • ptime
  • maxptime
  • maxinterleave—If not signaled, the maxinterleave length is set to 5.
  • silencesupp—If this parameter is not present, the default value 1 MUST be assumed.
  • dtxmax—See dtxmax in EVRC0 section.
  • dtxmin—See dtxmin in EVRC0 section.
  • hangover—See hangover in EVRC0 section.

The payload type is dynamic for this codec. The default ptime is 20 ms. The ptimes 20, 40, and 60 ms are supported for transcoding.

EVRC1 Supported Options

Required parameters: none

Optional parameters:

  • ptime—See RFC 4566
  • maxptime
  • fixedrate—Valid values are 0.5 or 1. If this parameter is not present, 0.5 is assumed.
  • silencesupp—If this parameter is not present, 1 MUST be assumed.
  • dtxmax—See dtxmax in EVRC0 section.
  • dtxmin—See dtxmin in EVRC0 section.
  • hangover—See hangover in EVRC0 section.

The payload type is dynamic for this codec. Only the 20 ms ptime is supported for transcoding. The media rate will be fixed to either full or half rate depending on the fixedrate parameter (half rate is default).

Default settings for EVRC encoding

  • CDMA Rate change for Dim and Burst disabled
  • CDMA DTX control enabled

EVRC Configuration

In the ACLI, refer to EVRC codecs exactly as follows:

EVRC0
EVRC
EVRC1

EVRC-B Codec for Transcoding

The Acme Packet 6300 supports the Enhanced Variable Rate codec, extension B (EVRCB) for transcoding. Three subtypes of the EVRCB codec are supported as media-profiles:

  • EVRCB0—This codec is transcodable.
  • EVRCB—This codec is transcodable.
  • EVRCB1—This codec is transcodable.

Note:

The Acme Packet 6300 handles optional parameters according to RFC 4788 unless otherwise specified.

EVRCB0 Supported Options

EVRBC0 is the header-free format of the EVRCB codec. Only a single frame (20 ms) is allowed in header-free mode.

Required Parameters: none

Optional Parameters:

  • silencesupp — If this parameter is not present in a DTX session, the default value 1 MUST be assumed.
  • dtxmax — If this parameter is not present in a DTX session, the default value is 32.
  • dtxmin — If this parameter is not present in a DTX session, the default value is 12.
  • hangover — If this parameter is not present in a DTX session, the default value 1 MUST be assumed.

The payload type is dynamic for this codec. EVRCB0 specifies the header-free format of the EVRCB codec. Only a single frame (20 ms) is allowed in header-free mode.

EVRCB Supported Options

Required Parameters: none

Optional parameters:

  • ptime
  • maxptime
  • maxinterleave—If not signaled, the maxinterleave length is set to 5.
  • silencesupp—If this parameter is not present, the default value 1 MUST be assumed.
  • dtxmax
  • dtxmin
  • hangover

The payload type is dynamic for this codec. The default ptime is 20 ms. Only the 20 ms ptime is supported for transcoding.

EVRCB1 Supported Options

Required parameters: none

Optional parameters:

  • ptime—See RFC 4566
  • maxptime
  • fixedrate—Valid values are 0.5 or 1. If this parameter is not present, 0.5 is assumed.
  • silencesupp—If this parameter is not present, 1 MUST be assumed.
  • dtxmax
  • dtxmin
  • hangover

The payload type is dynamic for this codec. Only the 20 ms ptime is supported for transcoding. The media rate will be fixed to either full or half rate depending on the fixedrate parameter (half rate is default).

Default fixed settings for EVRCB encoding

  • CDMA Rate change for Dim and Burst disabled
  • CDMA DTX control enabled

EVRCB Configuration

In the ACLI, refer to EVRCB codecs exactly as follows:

EVRCB0
EVRCB
EVRCB1