The table of contents (ToC) consists of one entry for each speech frame in the payload. A table of contents entry includes several specified fields as follows:
F (1 bit): Indicates if this frame is followed by further speech frames in this payload or not. F=1 further frames follow, F=0 last frame.
FT (4 bits): Frame type indicator, indicating the AMR or AMR-WB speech coding mode or comfort noise (SID) mode.If FT=14 (speech lost, available only in AMR-WB) or FT=15 (No transmission/no reception) no CRC or payload frame is present.
Q (1 bit): The payload quality bit indicates, if not set, that the payload is severely damaged and the receiver should set the RX_TYPE, see [6], to SPEECH_BAD or SID_BAD depending on the frame type (FT).
P: Is a padding bit, MUST be set to zero.
FIGURE 7 - Table of contents entry field for bandwidth efficient operation.
Figure 8 - An example of ToC when using bandwidth efficient operation.
Figure 9 - Table of contents entry field for octet aligned operation.
CRC (8 bits): OPTIONAL field, exists if the use of CRC is signaled at session set up and SHALL only be used in octet aligned operation. The 8 bit CRC is used for error detection. The algorithm to generate these 8 parity bits are defined in section 4.1.4 in [2].
Figure 10: CRC field
The ToC and CRCs are arranged with all table of contents entries fields first followed by all CRC fields. The ToC starts with the frame data belonging to the oldest speech frame.
Figure 11: The ToC and CRCs for a payload with three speech frames when using octet aligned operation.
references:
https://www.ietf.org/proceedings/51/I-D/draft-ietf-avt-rtp-amr-10.txt
F (1 bit): Indicates if this frame is followed by further speech frames in this payload or not. F=1 further frames follow, F=0 last frame.
FT (4 bits): Frame type indicator, indicating the AMR or AMR-WB speech coding mode or comfort noise (SID) mode.If FT=14 (speech lost, available only in AMR-WB) or FT=15 (No transmission/no reception) no CRC or payload frame is present.
Q (1 bit): The payload quality bit indicates, if not set, that the payload is severely damaged and the receiver should set the RX_TYPE, see [6], to SPEECH_BAD or SID_BAD depending on the frame type (FT).
P: Is a padding bit, MUST be set to zero.
FIGURE 7 - Table of contents entry field for bandwidth efficient operation.
Figure 8 - An example of ToC when using bandwidth efficient operation.
Figure 9 - Table of contents entry field for octet aligned operation.
CRC (8 bits): OPTIONAL field, exists if the use of CRC is signaled at session set up and SHALL only be used in octet aligned operation. The 8 bit CRC is used for error detection. The algorithm to generate these 8 parity bits are defined in section 4.1.4 in [2].
Figure 10: CRC field
The ToC and CRCs are arranged with all table of contents entries fields first followed by all CRC fields. The ToC starts with the frame data belonging to the oldest speech frame.
Figure 11: The ToC and CRCs for a payload with three speech frames when using octet aligned operation.
references:
https://www.ietf.org/proceedings/51/I-D/draft-ietf-avt-rtp-amr-10.txt
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