draft-ietf-avt-rtp-ipmr-08.txt   draft-ietf-avt-rtp-ipmr-09.txt 
Audio/Video Transport Working Group S. Ikonin Audio/Video Transport Working Group S. Ikonin
Internet Draft SPIRIT DSP Internet Draft SPIRIT DSP
Intended status: Informational September 16, 2009 Intended status: Informational September 28, 2009
RTP Payload Format for IP-MR Speech Codec draft-ietf-avt-rtp-ipmr-08.txt RTP Payload Format for IP-MR Speech Codec draft-ietf-avt-rtp-ipmr-09.txt
Status of this Memo Status of this Memo
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Abstract Abstract
This document specifies the payload format for packetization of SPIRIT This document specifies the payload format for packetization of SPIRIT
IP-MR encoded speech signals into the Real-time Transport Protocol IP-MR encoded speech signals into the Real-time Transport Protocol
(RTP). The payload format supports transmission of multiple frames per (RTP). The payload format supports transmission of multiple frames per
payload and introduced redundancy for robustness against packet loss. payload and introduced redundancy for robustness against packet loss.
Table of Contents Table of Contents
skipping to change at page 6, line 31 skipping to change at page 6, line 31
the packet SHOULD be discarded. the packet SHOULD be discarded.
o BR (3 bits): base rate for core layer of frame(s) in this packet o BR (3 bits): base rate for core layer of frame(s) in this packet
using the table for CR. Values in the range 0-5 indicate bitrates using the table for CR. Values in the range 0-5 indicate bitrates
for core layer, same as for packet SHOULD be discarded. The base for core layer, same as for packet SHOULD be discarded. The base
rate is the lowest rate for scalability, so speech payload can rate is the lowest rate for scalability, so speech payload can
be scaled down not lower than BR value. If a received packet has be scaled down not lower than BR value. If a received packet has
BR > CR then during decoding it will be assumed that BR = CR. BR > CR then during decoding it will be assumed that BR = CR.
o D (1 bit): indicates if the DTX mode is active or not. This o D (1 bit): indicates if the DTX mode is active or not. This
parameter is required for payload parsing. The parameter is retained for backward interoperability with previous
codec releases and required for payload parsing. The
decoder implementation MUST always include DTX mode decoder implementation MUST always include DTX mode
support and update internal states properly. The decoder cannot support and update internal states properly. The decoder cannot
assume that DTX will be constantly inactive during a session. assume that DTX will be constantly inactive during a session.
o A (1 bit): byte-aligned payload. If A=1 then all speech frames o A (1 bit): reserved. Must be always set to 1.
MUST be byte-aligned. This mode speeds up speech data access.
The A=0 value specifies bandwidth-efficient mode with no byte
alignment(including end of header).
o GR (2 bits): number of frames in packet (grouping size). Actual o GR (2 bits): number of frames in packet (grouping size). Actual
grouping size is GR + 1, thus maximum grouping supported is 4. grouping size is GR + 1, thus maximum grouping supported is 4.
o R (1 bit): redundancy presence bit. If R=1 then the packet o R (1 bit): redundancy presence bit. If R=1 then the packet
contains redundancy information for lost packets recovery. contains redundancy information for lost packets recovery.
In this case after speech data the redundancy section is present. In this case after speech data the redundancy section is present.
3.4. Speech Table of Contents 3.4. Speech Table of Contents
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