Internet DRAFT - draft-ietf-payload-melpe
draft-ietf-payload-melpe
Payload Working Group Victor Demjanenko
Internet-Draft David Satterlee
Intended Status: Standards Track VOCAL Technologies, Ltd.
Expires: August 11, 2017 February 7, 2017
RTP Payload Format for MELPe Codec
draft-ietf-payload-melpe-06
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Abstract
This document describes the RTP payload format for the Mixed
Excitation Linear Prediction Enhanced (MELPe) speech coder. MELPe's
three different speech encoding rates and sample frames sizes are
supported. Comfort noise procedures and packet loss concealment are
detailed.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Conventions, Definitions and Acronyms . . . . . . . . . . . 3
2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Payload Format . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1 MELPe Bitstream Definition . . . . . . . . . . . . . . . . 5
3.1.1 2400 bps Bitstream Structure . . . . . . . . . . . . . . 6
3.1.2 1200 bps Bitstream Structure . . . . . . . . . . . . . . 8
3.1.3 600 bps Bitstream Structure . . . . . . . . . . . . . . 11
3.2 MELPe Comfort Noise Bitstream Definition . . . . . . . . . 15
3.3 Multiple MELPe frames in a RTP packet . . . . . . . . . . . 17
3.4 Congestion Control Considerations . . . . . . . . . . . . . 19
4 Payload Format Parameters . . . . . . . . . . . . . . . . . . . 19
4.1 Media Type Definition . . . . . . . . . . . . . . . . . . . 20
4.2 Mapping to SDP . . . . . . . . . . . . . . . . . . . . . . 23
4.3 Declarative SDP Considerations . . . . . . . . . . . . . . 24
4.4 Offer/Answer SDP Considerations . . . . . . . . . . . . . . 24
5 Discontinious Transmission . . . . . . . . . . . . . . . . . . 25
6 Packet Loss Concealment . . . . . . . . . . . . . . . . . . . . 25
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 27
8 Security Considerations . . . . . . . . . . . . . . . . . . . . 27
9 RFC Editor Considerations . . . . . . . . . . . . . . . . . . . 27
10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
10.1 Normative References . . . . . . . . . . . . . . . . . . . 27
10.2 Informative References . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
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1 Introduction
This document describes how compressed MELPe speech as produced by
the MELPe codec may be formatted for use as an RTP payload. Details
are provided to packetize the three different codec bit-rate data
frames (2400, 1200, and 600) into RTP packets. The sender may send
one or more codec data frames per packet, depending on the
application scenario or based on the transport network condition,
bandwidth restriction, delay requirements and packet-loss tolerance.
1.1 Conventions, Definitions and Acronyms
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Best current practices for writing RTP payload format [RFC2736] were
followed.
2 Background
The MELP speech coder was developed by the US military as an upgrade
from LPC-based CELP standard vocoder for low bit-rate communications
[MELP]. MELP was further enhanced and subsequently adopted by NATO
as MELPe for use by its members and Partnership for Peace countries
for military and other governmental communications [MELPE]. The MELP
speech coder algorithm developed by Atlanta Signal Processing (ASPI),
Texas Instruments (TI), SignalCom (now Microsoft) and Thales
Communications with noise preprocessor contributions from AT&T under
contract with NSA/DOD as international NATO Standard STANAG 4591.
Commercial/civilian applications have arisen because of the low bit-
rate property of MELPe with its (relatively) high intelligibility.
As such MELPe is being used in a variety of wired and radio
communications systems. VoIP/SIP systems need to transport MELPe
without decoding and re-encoding in order to preserve its
intelligibility. Hence it is desirable and necessary to define the
proper payload formatting and use conventions of MELPe in RTP
payloads.
The MELPe codec [MELPE] supports three different vocoder bit rates;
2400, 1200, and 600 bps. The basic 2400 bps bit-rate vocoder uses a
22.5 ms frame of speech consisting of 180 8000 Hz, 16-bit speech
samples. The 1200 and 600 bps bit-rate vocoders uses respectively
three and four 22.5 ms frames of speech each. These reduced bit-rate
vocoders internally use multiple 2400 bps parameter sets with further
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processing to strategically remove redundancy. The payload sizes for
each of the bitrates are 54, 81, and 54 bits respectively for the
2400, 1200, and 600 bps frames. Dynamic bit-rate switching is
permitted but only if supported by both endpoints.
The MELPe algorithm distinguishes between voiced and un-voiced speech
and encodes each differently. Unvoiced speech can be coded with
fewer information bits for the same quality. Forward error
correction (FEC) is applied to the 2400 bps codec unvoiced speech for
better protection of the subtle differences in signal reconstruction.
The lower bit-rate coders do not allocate any bits for FEC and rely
on strong error protection and correction in the communications
channel.
Comfort noise handling for MELPe follows the procedures in SCIP-210
Appendix B [SCIP210]. After VAD no longer indicates the presence of
speech/voice, a grace period of a minimum of two comfort noise
vocoder fames are to be transmitted. The contents of the comfort
noise frames is described in the next section.
Packet loss concealment (PLC) exploits the FEC (and more precisely,
any combination of two set bits in the pitch/voicing parameter) of
the 2400 bps speech coder. The pitch/voicing parameter has a sparse
set of permitted values. A value of zero indicates a non-voiced
frame. At least three bits are set for all valid pitch parameters.
The PLC erasure indication utilizes any of the two bit set
errored/erasure encodings of a non-voiced frame as will be described
infra.
3 Payload Format
The MELPe codec uses 22.5, 67.5 or 90 ms frames with a sampling rate
clock of 8 kHz, so the RTP timestamp MUST be in units of 1/8000 of a
second.
The RTP payload for MELPe has the format shown in Figure 1. No
additional header specific to this payload format is needed. This
format is intended for the situations where the sender and the
receiver send one or more codec data frames per packet.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTP Header |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| |
+ one or more frames of MELPe |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 - Packet format diagram
The RTP header of the packetized encoded MELPe speech has the
expected values as described in [RFC3550]. The usage of M bit SHOULD
be as specified in the applicable RTP profile, for example, RFC 3551
[RFC3551], where [RFC3551] specifies that if the sender does not
suppress silence (i.e., sends a frame on every frame interval), the M
bit will always be zero. When more then one codec data frame is
present in a single RTP packet, the timestamp is, as always, that of
the oldest data frame represented in the RTP packet.
The assignment of an RTP payload type for this new packet format is
outside the scope of this document, and will not be specified here.
It is expected that the RTP profile for a particular class of
applications will assign a payload type for this encoding, or if that
is not done, then a payload type in the dynamic range shall be chosen
by the sender.
3.1 MELPe Bitstream Definition
The total number of bits used to describe one frame of 2400 bps
speech is 54, which fits in 7 octets (with two unused bits). For the
1200 bps speech the total number of bits used is 81, which fits in 11
octets (with seven unused bits). For the 600 bps speech the total
number of bits used is 54, which fits in 7 octets (with two unused
bits). Unused bits, shown below as RSVA, RSVB, etc., are coded as
described in 3.3 in support of dynamic bit-rate switching.
In the MELPe bitstream definition, the most significant bits are
considered priority bits. The intention was that these bits receive
greater protection in the underlying communications channel. For IP
networks, such additional protection is irrelevant. However, for
convenience of interoperable gateway devices, the bitstreams will be
presented identically in IP networks.
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3.1.1 2400 bps Bitstream Structure
According to Table 3 of [MELPE], the 2400 bit/s MELPe bit
transmission order (bit priority is not shown for clarity) is the
following:
+--------+-------------+-------------+
| Bit | Voiced | Unvoiced |
+--------+-------------+-------------+
| B_01 | g20 | g20 |
| B_02 | BP0 | FEC10 |
| B_03 | P0 | P0 |
| B_04 | LSF20 | LSF20 |
| B_05 | LSF30 | LSF30 |
| B_06 | g23 | g23 |
| B_07 | g24 | g24 |
| B_08 | LSF35 | LSF35 |
+--------+-------------+-------------+
| B_09 | g21 | g21 |
| B_10 | g22 | g22 |
| B_11 | P4 | P4 |
| B_12 | LSF34 | LSF34 |
| B_13 | P5 | P5 |
| B_14 | P1 | P1 |
| B_15 | P2 | P2 |
| B_16 | LSF40 | LSF40 |
+--------+-------------+-------------+
| B_17 | P6 | P6 |
| B_18 | LSF10 | LSF10 |
| B_19 | LSF16 | LSF16 |
| B_20 | LSF45 | LSF45 |
| B_21 | P3 | P3 |
| B_22 | LSF15 | LSF15 |
| B_23 | LSF14 | LSF14 |
| B_24 | LSF25 | LSF25 |
+--------+-------------+-------------+
| B_25 | BP3 | FEC13 |
| B_26 | LSF13 | LSF13 |
| B_27 | LSF12 | LSF12 |
| B_28 | LSF24 | LSF24 |
| B_29 | LSF44 | LSF44 |
| B_30 | FM0 | FEC40 |
| B_31 | LSF11 | LSF11 |
| B_32 | LSF23 | LSF23 |
+--------+-------------+-------------+
| B_33 | FM7 | FEC22 |
| B_34 | FM6 | FEC21 |
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| B_35 | FM5 | FEC20 |
| B_36 | g11 | g11 |
| B_37 | g10 | g10 |
| B_38 | BP2 | FEC12 |
| B_39 | BP1 | FEC11 |
| B_40 | LSF21 | LSF21 |
+--------+-------------+-------------+
| B_41 | LSF33 | LSF33 |
| B_42 | LSF22 | LSF22 |
| B_43 | LSF32 | LSF32 |
| B_44 | LSF31 | LSF31 |
| B_45 | LSF43 | LSF43 |
| B_46 | LSF42 | LSF42 |
| B_47 | AF | FEC42 |
| B_48 | LSF41 | LSF41 |
+--------+-------------+-------------+
| B_49 | FM4 | FEC32 |
| B_50 | FM3 | FEC31 |
| B_51 | FM2 | FEC30 |
| B_52 | FM1 | FEC41 |
| B_53 | g12 | g12 |
| B_54 | SYNC | SYNC |
+--------+-------------+-------------+
NOTES:
g = Gain
BP = Bandpass Voicing
P = Pitch/Voicing
LSF = Line Spectral Frequencies
FEC = Forward Error Correction Parity Bits
FM = Fourier Magnitudes
AF = Aperiodic Flag
B_01 = least significant bit of data set
Table 3.1 - The bitstream definition for MELPe 2400 bps.
The 2400 bps MELPe RTP payload is constructed as per Figure 2. Note
that bit B_01 is placed in the LSB of the first byte with all other
bits in sequence. When filling octets, the least significant bits of
the seventh octet are filled with bits B_49 to B_54 respectively.
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MSB LSB
0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+
| B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+
| B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 |
+------+------+------+------+------+------+------+------+
| B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 |
+------+------+------+------+------+------+------+------+
| B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 |
+------+------+------+------+------+------+------+------+
| B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 |
+------+------+------+------+------+------+------+------+
| RSVA | RSVB | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 |
+------+------+------+------+------+------+------+------+
Figure 2 - Packed MELPe 2400 bps payload octets.
3.1.2 1200 bps Bitstream Structure
According to Tables D9a and D9b of [MELPE], the 1200 bit/s MELPe bit
transmission order is the following:
+--------+-------------+-------------+
| Bit | Modes 1-4 | Mode 5 |
| | (Voiced) | (Unvoiced) |
+--------+-------------+-------------+
| B_01 | Syn | Syn |
| B_02 | Pitch&UV0 | Pitch&UV0 |
| B_03 | Pitch&UV1 | Pitch&UV1 |
| B_04 | Pitch&UV2 | Pitch&UV2 |
| B_05 | Pitch&UV3 | Pitch&UV3 |
| B_06 | Pitch&UV4 | Pitch&UV4 |
| B_07 | Pitch&UV5 | Pitch&UV5 |
| B_08 | Pitch&UV6 | Pitch&UV6 |
+--------+-------------+-------------+
| B_09 | Pitch&UV7 | Pitch&UV7 |
| B_10 | Pitch&UV8 | Pitch&UV8 |
| B_11 | Pitch&UV9 | Pitch&UV9 |
| B_12 | Pitch&UV10 | Pitch&UV10 |
| B_13 | Pitch&UV11 | Pitch&UV11 |
| B_14 | LSP0 | LSP0 |
| B_15 | LSP1 | LSP1 |
| B_16 | LSP2 | LSP2 |
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+--------+-------------+-------------+
| B_17 | LSP3 | LSP3 |
| B_18 | LSP4 | LSP4 |
| B_19 | LSP5 | LSP5 |
| B_20 | LSP6 | LSP6 |
| B_21 | LSP7 | LSP7 |
| B_22 | LSP8 | LSP8 |
| B_23 | LSP9 | LSP9 |
| B_24 | LSP10 | LSP10 |
+--------+-------------+-------------+
| B_25 | LSP11 | LSP11 |
| B_26 | LSP12 | LSP12 |
| B_27 | LSP13 | LSP13 |
| B_28 | LSP14 | LSP14 |
| B_29 | LSP15 | LSP15 |
| B_30 | LSP16 | LSP16 |
| B_31 | LSP17 | LSP17 |
| B_32 | LSP18 | LSP18 |
+--------+-------------+-------------+
| B_33 | LSP19 | LSP19 |
| B_34 | LSP20 | LSP20 |
| B_35 | LSP21 | LSP21 |
| B_36 | LSP22 | LSP22 |
| B_37 | LSP23 | LSP23 |
| B_38 | LSP24 | LSP24 |
| B_39 | LSP25 | LSP25 |
| B_40 | LSP26 | LSP26 |
+--------+-------------+-------------+
| B_41 | LSP27 | GAIN0 |
| B_42 | LSP28 | GAIN1 |
| B_43 | LSP29 | GAIN2 |
| B_44 | LSP30 | GAIN3 |
| B_45 | LSP31 | GAIN4 |
| B_46 | LSP32 | GAIN5 |
| B_47 | LSP33 | GAIN6 |
| B_48 | LSP34 | GAIN7 |
+--------+-------------+-------------+
| B_49 | LSP35 | GAIN8 |
| B_50 | LSP36 | GAIN9 |
| B_51 | LSP37 | |
| B_52 | LSP38 | |
| B_53 | LSP39 | |
| B_54 | LSP40 | |
| B_55 | LSP41 | |
| B_56 | LSP42 | |
+--------+-------------+-------------+
| B_57 | GAIN0 | |
| B_58 | GAIN1 | |
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| B_59 | GAIN2 | |
| B_60 | GAIN3 | |
| B_61 | GAIN4 | |
| B_62 | GAIN5 | |
| B_63 | GAIN6 | |
| B_64 | GAIN7 | |
+--------+-------------+-------------+
| B_65 | GAIN8 | |
| B_66 | GAIN9 | |
| B_67 | BP0 | |
| B_68 | BP1 | |
| B_69 | BP2 | |
| B_70 | BP3 | |
| B_71 | BP4 | |
| B_72 | BP5 | |
+--------+-------------+-------------+
| B_73 | JITTER | |
| B_74 | FS0 | |
| B_75 | FS1 | |
| B_76 | FS2 | |
| B_77 | FS3 | |
| B_78 | FS4 | |
| B_79 | FS5 | |
| B_80 | FS6 | |
+--------+-------------+-------------+
| B_81 | FS7 | |
+--------+-------------+-------------+
NOTES:
BP = Band pass voicing
FS = Fourier magnitudes
Table 3.2 - The bitstream definition for MELPe 1200 bps.
The 1200 bps MELPe RTP payload is constructed as per Figure 3. Note
that bit B_01 is placed in the LSB of the first byte with all other
bits in sequence. When filling octets, the least significant bit of
the eleventh octet is filled with bit B_81.
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MSB LSB
0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+
| B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+
| B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 |
+------+------+------+------+------+------+------+------+
| B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 |
+------+------+------+------+------+------+------+------+
| B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 |
+------+------+------+------+------+------+------+------+
| B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 |
+------+------+------+------+------+------+------+------+
| B_56 | B_55 | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 |
+------+------+------+------+------+------+------+------+
| B_64 | B_63 | B_62 | B_61 | B_60 | B_59 | B_58 | B_57 |
+------+------+------+------+------+------+------+------+
| B_72 | B_71 | B_70 | B_69 | B_68 | B_67 | B_66 | B_65 |
+------+------+------+------+------+------+------+------+
| B_80 | B_79 | B_78 | B_77 | B_76 | B_75 | B_74 | B_73 |
+------+------+------+------+------+------+------+------+
| RSVA | RSVB | RSVC | RSV0 | RSV0 | RSV0 | RSV0 | B_81 |
+------+------+------+------+------+------+------+------+
Figure 3 - Packed MELPe 1200 bps payload octets.
3.1.3 600 bps Bitstream Structure
According to Tables M-11 to M-16 of [MELPE], the 600 bit/s MELPe bit
transmission order (bit priority is not shown for clarity) is the
following:
+--------+-------------+-------------+-------------+
| Bit | Mode 1 | Mode 2 | Mode 3 |
| | (Voiced) | (voiced) | (voiced) |
+--------+-------------+-------------+-------------+
| B_01 | Voicing (4) | Voicing (4) | Voicing (4) |
| B_02 | Voicing (3) | Voicing (3) | Voicing (3) |
| B_03 | Voicing (2) | Voicing (2) | Voicing (2) |
| B_04 | Voicing (1) | Voicing (1) | Voicing (1) |
| B_05 | Voicing (0) | Voicing (0) | Voicing (0) |
| B_06 | LSF1,4 (3) | Pitch (5) | Pitch (7) |
| B_07 | LSF1,4 (2) | Pitch (4) | Pitch (6) |
| B_08 | LSF1,4 (1) | Pitch (3) | Pitch (5) |
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+--------+-------------+-------------+-------------+
| B_09 | LSF1,4 (0) | Pitch (2) | Pitch (4) |
| B_10 | LSF1,3 (3) | Pitch (1) | Pitch (3) |
| B_11 | LSF1,3 (2) | Pitch (0) | Pitch (2) |
| B_12 | LSF1,3 (1) | LSF1,3 (3) | Pitch (1) |
| B_13 | LSF1,3 (0) | LSF1,3 (2) | Pitch (0) |
| B_14 | LSF1,2 (3) | LSF1,3 (1) | LSF1,3 (3) |
| B_15 | LSF1,2 (2) | LSF1,3 (0) | LSF1,3 (2) |
| B_16 | LSF1,2 (1) | LSF1,2 (3) | LSF1,3 (1) |
+--------+-------------+-------------+-------------+
| B_17 | LSF1,2 (0) | LSF1,2 (2) | LSF1,3 (0) |
| B_18 | LSF1,1 (5) | LSF1,2 (1) | LSF1,2 (4) |
| B_19 | LSF1,1 (4) | LSF1,2 (0) | LSF1,2 (3) |
| B_20 | LSF1,1 (3) | LSF1,1 (5) | LSF1,2 (2) |
| B_21 | LSF1,1 (2) | LSF1,1 (4) | LSF1,2 (1) |
| B_22 | LSF1,1 (1) | LSF1,1 (3) | LSF1,2 (0) |
| B_23 | LSF1,1 (0) | LSF1,1 (2) | LSF1,1 (5) |
| B_24 | LSF2,4 (3) | LSF1,1 (1) | LSF1,1 (4) |
+--------+-------------+-------------+-------------+
| B_25 | LSF2,4 (2) | LSF1,1 (0) | LSF1,1 (3) |
| B_26 | LSF2,4 (1) | LSF2,3 (3) | LSF1,1 (2) |
| B_27 | LSF2,4 (0) | LSF2,3 (2) | LSF1,1 (1) |
| B_28 | LSF2,3 (3) | LSF2,3 (1) | LSF1,1 (0) |
| B_29 | LSF2,3 (2) | LSF2,3 (0) | LSF2,3 (3) |
| B_30 | LSF2,3 (1) | LSF2,2 (4) | LSF2,3 (2) |
| B_31 | LSF2,3 (0) | LSF2,2 (3) | LSF2,3 (1) |
| B_32 | LSF2,2 (3) | LSF2,2 (2) | LSF2,3 (0) |
+--------+-------------+-------------+-------------+
| B_33 | LSF2,2 (2) | LSF2,2 (1) | LSF2,2 (4) |
| B_34 | LSF2,2 (1) | LSF2,2 (0) | LSF2,2 (3) |
| B_35 | LSF2,2 (0) | LSF2,1 (6) | LSF2,2 (2) |
| B_36 | LSF2,1 (5) | LSF2,1 (5) | LSF2,2 (1) |
| B_37 | LSF2,1 (4) | LSF2,1 (4) | LSF2,2 (0) |
| B_38 | LSF2,1 (3) | LSF2,1 (3) | LSF2,1 (5) |
| B_39 | LSF2,1 (2) | LSF2,1 (2) | LSF2,1 (4) |
| B_40 | LSF2,1 (1) | LSF2,1 (1) | LSF2,1 (3) |
+--------+-------------+-------------+-------------+
| B_41 | LSF2,1 (0) | LSF2,1 (0) | LSF2,1 (2) |
| B_42 | GAIN2 (5) | GAIN2 (5) | LSF2,1 (1) |
| B_43 | GAIN2 (4) | GAIN2 (4) | LSF2,1 (0) |
| B_44 | GAIN2 (3) | GAIN2 (3) | GAIN2 (4) |
| B_45 | GAIN2 (2) | GAIN2 (2) | GAIN2 (3) |
| B_46 | GAIN2 (1) | GAIN2 (1) | GAIN2 (2) |
| B_47 | GAIN2 (0) | GAIN2 (0) | GAIN2 (1) |
| B_48 | GAIN1 (6) | GAIN1 (6) | GAIN2 (0) |
+--------+-------------+-------------+-------------+
| B_49 | GAIN1 (5) | GAIN1 (5) | GAIN1 (5) |
| B_50 | GAIN1 (4) | GAIN1 (4) | GAIN1 (4) |
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| B_51 | GAIN1 (3) | GAIN1 (3) | GAIN1 (3) |
| B_52 | GAIN1 (2) | GAIN1 (2) | GAIN1 (2) |
| B_53 | GAIN1 (1) | GAIN1 (1) | GAIN1 (1) |
| B_54 | GAIN1 (0) | GAIN1 (0) | GAIN1 (0) |
+--------+-------------+-------------+-------------+
Table 3.3a - The bitstream definition for MELPe 600 bps (part 1 of
2).
+--------+-------------+-------------+-------------+
| Bit | Mode 4 | Mode 5 | Mode 6 |
| | (voiced) | (voiced) | (voiced) |
+--------+-------------+-------------+-------------+
| B_01 | Voicing (4) | Voicing (4) | Voicing (4) |
| B_02 | Voicing (3) | Voicing (3) | Voicing (3) |
| B_03 | Voicing (2) | Voicing (2) | Voicing (2) |
| B_04 | Voicing (1) | Voicing (1) | Voicing (1) |
| B_05 | Voicing (0) | Voicing (0) | Voicing (0) |
| B_06 | Pitch (7) | Pitch (7) | Pitch (7) |
| B_07 | Pitch (6) | Pitch (6) | Pitch (6) |
| B_08 | Pitch (5) | Pitch (5) | Pitch (5) |
+--------+-------------+-------------+-------------+
| B_09 | Pitch (4) | Pitch (4) | Pitch (4) |
| B_10 | Pitch (3) | Pitch (3) | Pitch (3) |
| B_11 | Pitch (2) | Pitch (2) | Pitch (2) |
| B_12 | Pitch (1) | Pitch (1) | Pitch (1) |
| B_13 | Pitch (0) | Pitch (0) | Pitch (0) |
| B_14 | LSF1,3 (3) | LSF1,3 (3) | LSF1,3 (3) |
| B_15 | LSF1,3 (2) | LSF1,3 (2) | LSF1,3 (2) |
| B_16 | LSF1,3 (1) | LSF1,3 (1) | LSF1,3 (1) |
+--------+-------------+-------------+-------------+
| B_17 | LSF1,3 (0) | LSF1,3 (0) | LSF1,3 (0) |
| B_18 | LSF1,2 (3) | LSF1,2 (4) | LSF1,2 (4) |
| B_19 | LSF1,2 (2) | LSF1,2 (3) | LSF1,2 (3) |
| B_20 | LSF1,2 (1) | LSF1,2 (2) | LSF1,2 (2) |
| B_21 | LSF1,2 (0) | LSF1,2 (1) | LSF1,2 (1) |
| B_22 | LSF1,1 (5) | LSF1,2 (0) | LSF1,2 (0) |
| B_23 | LSF1,1 (4) | LSF1,1 (5) | LSF1,1 (6) |
| B_24 | LSF1,1 (3) | LSF1,1 (4) | LSF1,1 (5) |
+--------+-------------+-------------+-------------+
| B_25 | LSF1,1 (2) | LSF1,1 (3) | LSF1,1 (4) |
| B_26 | LSF1,1 (1) | LSF1,1 (2) | LSF1,1 (3) |
| B_27 | LSF1,1 (0) | LSF1,1 (1) | LSF1,1 (2) |
| B_28 | LSF2,3 (3) | LSF1,1 (0) | LSF1,1 (1) |
| B_29 | LSF2,3 (2) | LSF2,3 (3) | LSF1,1 (0) |
| B_30 | LSF2,3 (1) | LSF2,3 (2) | LSF2,3 (3) |
| B_31 | LSF2,3 (0) | LSF2,3 (1) | LSF2,3 (2) |
| B_32 | LSF2,2 (4) | LSF2,3 (0) | LSF2,3 (1) |
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+--------+-------------+-------------+-------------+
| B_33 | LSF2,2 (3) | LSF2,2 (4) | LSF2,3 (0) |
| B_34 | LSF2,2 (2) | LSF2,2 (3) | LSF2,2 (4) |
| B_35 | LSF2,2 (1) | LSF2,2 (2) | LSF2,2 (3) |
| B_36 | LSF2,2 (0) | LSF2,2 (1) | LSF2,2 (2) |
| B_37 | LSF2,1 (6) | LSF2,2 (0) | LSF2,2 (1) |
| B_38 | LSF2,1 (5) | LSF2,1 (5) | LSF2,2 (0) |
| B_39 | LSF2,1 (4) | LSF2,1 (4) | LSF2,1 (6) |
| B_40 | LSF2,1 (3) | LSF2,1 (3) | LSF2,1 (5) |
+--------+-------------+-------------+-------------+
| B_41 | LSF2,1 (2) | LSF2,1 (2) | LSF2,1 (4) |
| B_42 | LSF2,1 (1) | LSF2,1 (1) | LSF2,1 (3) |
| B_43 | LSF2,1 (0) | LSF2,1 (0) | LSF2,1 (2) |
| B_44 | GAIN2 (4) | GAIN2 (4) | LSF2,1 (1) |
| B_45 | GAIN2 (3) | GAIN2 (3) | LSF2,1 (0) |
| B_46 | GAIN2 (2) | GAIN2 (2) | GAIN1 (8) |
| B_47 | GAIN2 (1) | GAIN2 (1) | GAIN1 (7) |
| B_48 | GAIN2 (0) | GAIN2 (0) | GAIN1 (6) |
+--------+-------------+-------------+-------------+
| B_49 | GAIN1 (5) | GAIN1 (5) | GAIN1 (5) |
| B_50 | GAIN1 (4) | GAIN1 (4) | GAIN1 (4) |
| B_51 | GAIN1 (3) | GAIN1 (3) | GAIN1 (3) |
| B_52 | GAIN1 (2) | GAIN1 (2) | GAIN1 (2) |
| B_53 | GAIN1 (1) | GAIN1 (1) | GAIN1 (1) |
| B_54 | GAIN1 (0) | GAIN1 (0) | GAIN1 (0) |
+--------+-------------+-------------+-------------+
Notes:
xxxx (0) = LSB
xxxx (nbits-1) = MSB
LSF1,p = MSVQ indice of the pth stage of the two first frames
LSF2,p = MSVQ indice of the pth stage of the two last frames
GAIN1 = VQ/MSVQ indice of the 1st stage
GAIN2 = MSVQ indice of the 2nd stage
Table 3.3b - The bitstream definition for MELPe 600 bps (part 2 of
2).
The 600 bps MELPe RTP payload is constructed as per Figure 4. Note
that bit B_01 is placed in the LSB of the first byte with all other
bits in sequence. When filling octets, the least significant bits of
the seventh octet are filled with bits B_49 to B_54 respectively.
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MSB LSB
0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+
| B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+
| B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 |
+------+------+------+------+------+------+------+------+
| B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 |
+------+------+------+------+------+------+------+------+
| B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 |
+------+------+------+------+------+------+------+------+
| B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 |
+------+------+------+------+------+------+------+------+
| RSVA | RSVB | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 |
+------+------+------+------+------+------+------+------+
Figure 4 - Packed MELPe 600 bps payload octets.
3.2 MELPe Comfort Noise Bitstream Definition
Table B.3-1 of [SCIP210] identifies the usage of MELPe 2400 bps
parameters for conveying comfort noise.
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+-------------------------------------+----------------+
| MELPe Parameter | Value |
+-------------------------------------+----------------+
| msvq[0] (line spectral frequencies) | * See Note |
+-------------------------------------+----------------+
| msvq[1] (line spectral frequencies) | Set to 0 |
+-------------------------------------+----------------+
| msvq[2] (line spectral frequencies) | Set to 0 |
+-------------------------------------+----------------+
| msvq[3] (line spectral frequencies) | Set to 0 |
+-------------------------------------+----------------+
| fsvq (Fourier magnitudes) | Set to 0 |
+-------------------------------------+----------------+
| gain[0] (gain) | Set to 0 |
+-------------------------------------+----------------+
| gain[1] (gain) | * See Note |
+-------------------------------------+----------------+
| pitch (pitch - overall voicing) | Set to 0 |
+-------------------------------------+----------------+
| bp (bandpass voicing) | Set to 0 |
+-------------------------------------+----------------+
| af (aperiodic flag/jitter index) | Set to 0 |
+-------------------------------------+----------------+
| sync (sync bit) | Alternations |
+-------------------------------------+----------------+
Note: The default values are the respective parameters from
the vocoder frame. It is preferred that msvq[0] and gain[1]
values be derived by averaging the respective parameter from
some number of previous vocoder frames.
Table 3.4 - MELPe Comfort Noise Parameters
Since only msvq[0] (also known as LSF1x or the first LSP) and gain[1]
(also known as g2x or the second gain) are needed, the following bit
order is used for comfort noise frames.
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+--------+-------------+
| Bit | Comfort |
| | Noise |
+--------+-------------+
| B_01 | LSF10 |
| B_02 | LSF11 |
| B_03 | LSF12 |
| B_04 | LSF13 |
| B_05 | LSF14 |
| B_06 | LSF15 |
| B_07 | LSF16 |
| B_08 | g20 |
+--------+-------------+
| B_09 | g21 |
| B_10 | g22 |
| B_11 | g23 |
| B_12 | g24 |
| B_13 | SYNC |
+--------+-------------+
NOTES:
g = Gain
LSF = Line Spectral Frequencies
Table 3.5 - The bitstream definition for MELPe Comfort Noise.
The Comfort Noise MELPe RTP payload is constructed as per Figure 5.
Note that bit B_01 is placed in the LSB of the first byte with all
other bits in sequence. When When filling octets, the least
significant bits of the second octet are filled with bits B_09 to
B_13 respectively.
MSB LSB
0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+
| RSVA | RSVB | RSVC | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+
Figure 5 - Packed MELPe Comfort Noise payload octets.
3.3 Multiple MELPe frames in a RTP packet
A MELPe RTP packet MAY consist of zero or more MELPe coder frames,
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followed by zero or one MELPe Comfort Noise frames. The presence of
a comfort noise frame can be deduced from the length of the RTP
payload. The default packetization interval is one coder frame
(22.5, 67.5 or 90 ms) according to the coder bit rate (2400, 1200 or
600 bps). For some applications, a longer packetization interval is
used to reduce the packet rate.
A MELPe RTP packet comprised of no coder frame and no comfort noise
frame MAY be used periodically by an end point to indicate
connectivity by an otherwise idle receiver.
All MELPe frames in a single RTP packet MUST be of the same coder bit
rate. Dynamic switching between frame rates within an RTP stream may
be permitted (if supported by both ends) provided that reserved bits,
RSVA, RSVB, and RSVC are filled in as per Table 3.6. If bit-rate
switching is not used, all reserved bits are encoded as 0 by the
sender and ignored by the receiver. (RSV0 is always coded as 0).
+-------------------+------+------+------+
| Coder Bit Rate | RSVA | RSVB | RSVC |
+-------------------+------+------+------+
| 2400 bps | 0 | 0 | N/A |
+-------------------+------+------+------+
| 1200 bps | 1 | 0 | 0 |
+-------------------+------+------+------+
| 600 bps | 0 | 1 | N/A |
+-------------------+------+------+------+
| Comfort Noise | 1 | 0 | 1 |
+-------------------+------+------+------+
| (reserved) | 1 | 1 | N/A |
+-------------------+------+------+------+
Table 3.6 - MELPe Frame Bit Rate Indicators.
It is important to observe that senders have the following additional
restrictions:
Senders SHOULD NOT include more MELPe frames in a single RTP packet
than will fit in the MTU of the RTP transport protocol.
Frames MUST NOT be split between RTP packets.
It is RECOMMENDED that the number of frames contained within an RTP
packet is consistent with the application. For example, in a
telephony and other real time applications where delay is important,
then the fewer frames per packet the lower the delay, whereas for
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bandwidth constrained links or delay insensitive streaming messaging
application, more than one or many frames per packet would be
acceptable.
Information describing the number of frames contained in an RTP
packet is not transmitted as part of the RTP payload. The way to
determine the number of MELPe frames is to count the total number of
octets within the RTP packet, and divide the octet count by the
number of expected octets per frame (7/11/7 per frame). Keep in mind
the last frame can be a 2 octet comfort noise frame.
When dynamic bit-rate switching is used and more than one frame is
contained in a RTP packet, it is RECOMMENDED to inspect the coder
rate bits contained in the last octet. If the coder bit rate
indicates a Comfort Noise frame, then inspect the third last octet
for the coder bit rate. All MELPe speech frames in the RTP packet
will be of this same coder bit rate.
3.4 Congestion Control Considerations
The target bitrate of MELPe can be adjusted at any point in time,
thus allowing congestion management. Furthermore, the amount of
encoded speech or audio data encoded in a single packet can be used
for congestion control, since packet rate is inversely proportional
to the packet duration. A lower packet transmission rate reduces the
amount of header overhead, but at the same time increases latency and
loss sensitivity, so it ought to be used with care.
Since UDP does not provide congestion control, applications that use
RTP over UDP SHOULD implement their own congestion control above the
UDP layer [RFC8085] and MAY as well implement a transport circuit
breaker [RFC8083] (formerly [draft-ietf-avtcore-rtp-circuit-
breakers]). Work in the RMCAT working group [rmcat] describes the
interactions and conceptual interfaces necessary between the
application components that relate to congestion control, including
the RTP layer, the higher-level media codec control layer, and the
lower-level transport interface, as well as components dedicated to
congestion control functions.
4 Payload Format Parameters
This RTP payload format is identified using the MELP, MELP2400,
MELP1200, and MELP600 media types which is registered in accordance
with RFC 4855 [RFC4855] and using the template of RFC 6838 [RFC6838].
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4.1 Media Type Definition
Type names:
audio
Subtype name:
MELP, MELP2400, MELP1200, and MELP600
Required parameters:
N/A
Optional parameters:
ptime: the recommended length of time (in milliseconds)
represented by the media in a packet. It SHALL use the nearest
rounded-up ms integer packet duration. For MELPe, this
corresponds to the values: 23, 45, 68, 90, 112, 135, 156, and
180. Larger values can be used as long as they are properly
rounded. See Section 6 of RFC 4566 [RFC4566].
maxptime: the maximum length of time (in milliseconds) that can
be encapsulated in a packet. It SHALL use the nearest rounded-
up ms integer packet duration. For MELPe, this corresponds to
the values: 23, 45, 68, 90, 112, 135, 156, and 180. Larger
values can be used as long as they are properly rounded. See
Section 6 of RFC 4566 [RFC4566].
bitrate: specifies the MELPe coder bit rates supported.
Possible values are a comma-separated list of rates from the
set: 2400, 1200, 600. The modes are listed in order of
preference; first is preferred. If "bitrate" is not present,
the fixed coder bit rate of 2400 MUST be used. The alternate
encoding names, "MELP2400", "MELP1200", and "MELP600" directly
specify the MELPe coder bit rate of 2400, 1200, and 600
respectively and MUST NOT specify a "bitrate" parameter.
Encoding considerations:
This media type is framed and binary, see section 4.8 in RFC6838
[RFC6838].
Security considerations:
Please see the security considerations in section 8 of RFCxxxx
(this RFC).
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Interoperability considerations:
Early implementations used MELP2400, MELP1200, and MELP600 to
indicate both coder type and bit rate. These media type names
should be preserved with this registration.
Published specification:
N/A
Applications that use this media type:
N/A
Additional information:
N/A
Deprecated alias names for this type:
N/A
Magic number(s):
N/A
File extension(s):
N/A
Macintosh file type code(s):
N/A
Person & email address to contact for further information:
Victor Demjanenko, Ph.D.
VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202
Buffalo, NY 14228
USA
Phone: +1 716 688 4675
Email: victor.demjanenko@vocal.com
Intended usage:
COMMON
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Restrictions on usage:
This media type depends on RTP framing, and hence is only defined
for transfer via RTP [RFC3550]. Transport within other framing
protocols is not defined at this time.
Author:
Victor Demjanenko
Change controller:
IETF Payload working group delegated from the IESG.
Provisional registration? (standards tree only):
No
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4.2 Mapping to SDP
The mapping of the above defined payload format media type and its
parameters SHALL be done according to Section 3 of RFC 4855
[RFC4855].
The information carried in the media type specification has a
specific mapping to fields in the Session Description Protocol (SDP)
[RFC4566], which is commonly used to describe RTP sessions. When SDP
is used to specify sessions employing the MELPe codec, the mapping is
as follows:
o The media type ("audio") goes in SDP "m=" as the media name.
o The media subtype (payload format name) goes in SDP "a=rtpmap"
as the encoding name.
o The parameter "bitrate" goes in the SDP "a=fmtp" attribute by
copying it as a "bitrate=<value>" string.
o The parameters "ptime" and "maxptime" go in the SDP "a=ptime"
and "a=maxptime" attributes, respectively.
When conveying information by SDP, the encoding name SHALL be "MELP"
(the same as the media subtype). Alternative encoding name types,
"MELP2400", "MELP1200", and "MELP600", MAY be used in SDP to convey
fixed bit-rate configurations. These names have been observed in
systems that do not support dynamic frame rate switching as specified
by the parameter, "bitrate".
An example of the media representation in SDP for describing MELPe
might be:
m=audio 49120 RTP/AVP 97
a=rtpmap:97 MELP/8000
An alternative example of SDP for fixed bit-rate configurations might
be:
m=audio 49120 RTP/AVP 97 100 101 102
a=rtpmap:97 MELP/8000
a=rtpmap:100 MELP2400/8000
a=rtpmap:101 MELP1200/8000
a=rtpmap:102 MELP600/8000
If the encoding name "MELP" is received without a "bitrate"
parameter, the fixed coder bit rate of 2400 MUST be used. The
alternate encoding names, "MELP2400", "MELP1200", and "MELP600"
directly specify the MELPe coder bit rate of 2400, 1200, and 600
respectively and MUST NOT specify a "bitrate" parameter.
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The optional media type parameter, "bitrate", when present, MUST be
included in the "a=fmtp" attribute in the SDP, expressed as a media
type string in the form of a semicolon-separated list of
parameter=value pairs. The string, "value", can be one or more of
2400, 1200, and 600 separated by commas (where each bit-rate value
indicates the corresponding MELPe coder). An example of the media
representation in SDP for describing MELPe when all three coder bit
rates are supported might be:
m=audio 49120 RTP/AVP 97
a=rtpmap:97 MELP/8000
a=fmtp:97 bitrate=2400,600,1200
Parameter ptime can not be used for the purpose of specifying MELPe
operating mode, due to fact that for the certain values it will be
impossible to distinguish which mode is about to be used (e.g. when
ptime=68, it would be impossible to distinguish if packet is carrying
1 frames of 67.5 ms or 3 frames of 22.5 ms etc.).
Note that the payload format (encoding) names are commonly shown in
upper case. Media subtypes are commonly shown in lower case. These
names are case-insensitive in both places. Similarly, parameter
names are case-insensitive both in media subtype name and in the
default mapping to the SDP a=fmtp attribute
4.3 Declarative SDP Considerations
For declarative media, the "bitrate" parameter specifes the possible
bit rates used by the sender. Multiple MELPe rtpmap values (such as
97, 98, and 99 as used below) MAY be used to convey MELPe coded voice
at different bit rates. The receiver can then select an appropriate
MELPe codec by using 97, 98, or 99.
m=audio 49120 RTP/AVP 97 98 99
a=rtpmap:97 MELP/8000
a=fmtp:97 bitrate=2400
a=rtpmap:98 MELP/8000
a=fmtp:98 bitrate=1200
a=rtpmap:99 MELP/8000
a=fmtp:99 bitrate=600
4.4 Offer/Answer SDP Considerations
In an Offer/Answer mode [RFC3264], "bitrate" is a bi-directional
parameter. Both sides MUST use a common "bitrate" value or values.
The offer contains the bit rates supported by the offerer listed in
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its preferred order. The answerer MAY agree to any bit rate by
listing the bit rate first in the answerer response. Additionally
the answerer MAY indicate any secondary bit rate or bit rates that it
supports. The initial bit rate used by both parties SHALL be the
first bit rate specified in the answerer response.
For example if offerer bit rates are "2400,600", and answer bit rates
are "600,2400", the initial bit rate is 600. If other bit rates are
provided by the answerer, any common bit rate between offer and
answer MAY be used at any time in the future. Activation of these
other common bit rates is beyond the scope of this document.
The use of a lower bit rate is often important for a case such as
when one end point utilizes a bandwidth constrained link (e.g. 1200
bps radio link or slower), where only the lower coder bit rate will
work.
5 Discontinious Transmission
A primary application of MELPe is for radio communications of voice
conversations and discontinuous transmissions are normal. When MELPe
is used in an IP network, MELPe RTP packet transmissions may cease
and resume frequently. RTP SSRC sequence number gaps indicate lost
packets to be filled by PLC while abrupt loss of RTP packets indicate
intended discontinuous transmission.
If a MELPe coder so desires, it may send a comfort noise frame as per
SCIP-210 Appendix B [SCIP210] prior to ceasing transmission. A
receiver may optionally use comfort noise during its silence periods.
No SDP negotiations are required.
6 Packet Loss Concealment
MELPe packet loss concealment (PLC) uses the special properties and
coding for the pitch/voicing parameter of the MELPe 2400 bps coder.
The PLC erasure indication utilizes any of the errored encodings of a
non-voiced frame as identified in Table 1 of [MELPE]. For the sake
of simplicity it is preferred to use a code value of 3 for the
pitch/voicing parameter (represented by the bits P6 to P0 in Table
3.1). Hence, set bits P0 and P1 to one and bits P2, P3, P4, P5, and
P6 to zero.
When using PLC in a 1200 bps or 600 bps mode, the MELPe 2400 bps
decoder is called three or four times respectively to cover the loss
of a MELPe frame.
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7 IANA Considerations
This memo requests that IANA registers MELP, MELP2400, MELP1200, and
MELP600 as specified in Section 4.1. The media type is also
requested to be added to the IANA registry for "RTP Payload Format
MIME types" (http://www.iana.org/assignments/rtp-parameters).
8 Security Considerations
RTP packets using the payload format defined in this specification
are subject to the security considerations discussed in the RTP
specification [RFC3550], and in any applicable RTP profile such as
RTP/AVP [RFC3551], RTP/AVPF [RFC4855], RTP/SAVP [RFC3711] or
RTP/SAVPF [RFC5124]. However, as "Securing the RTP Protocol
Framework: Why RTP Does Not Mandate a Single Media Security Solution"
[RFC7202] discusses, it is not an RTP payload format's responsibility
to discuss or mandate what solutions are used to meet the basic
security goals like confidentiality, integrity and source
authenticity for RTP in general. This responsibility lays on anyone
using RTP in an application. They can find guidance on available
security mechanisms and important considerations in Options for
Securing RTP Sessions [RFC7201]. Applications SHOULD use one or more
appropriate strong security mechanisms. The rest of this security
consideration section discusses the security impacting properties of
the payload format itself.
This RTP payload format and the MELPe decoder do not exhibit any
significant non-uniformity in the receiver-side computational
complexity for packet processing, and thus are unlikely to pose a
denial-of-service threat due to the receipt of pathological data.
Nor does the RTP payload format contain any active content.
With respect to VAD and its effect on bit rate, please see security
consideration in RFC6562 [RFC6562].
9 RFC Editor Considerations
Note to RFC Editor: This section may be removed after carrying out
all the instructions of this section.
10 References
10.1 Normative References
[draft-ietf-avtcore-rtp-circuit-breakers] Perkins, C. and V. Singh,
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"Multimedia Congestion Control: Circuit Breakers for Unicast RTP
Sessions", draft-ietf-avtcore-rtp-circuit-breakers-18 (work in
progress), August 18, 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2736] Handley, M. and Perkins, C., "Guidelines for Writers of RTP
Payload Format Specifications", BCP 36, RFC 2736, December 1999.
[RFC3264] Rosenberg, J. and Schulzrinne, H., "An Offer/Answer Model
with the Session Description Protocol (SDP)" IETF RFC 3264, June
2002.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and Jacobson,
V., "RTP: A Transport Protocol for Real-Time Applications", IETF RFC
3550, July 2003.
[RFC3551] Schulzrinne, H., and Casner, S., "RTP Profile for Audio and
Video Conferences with Minimal Control" IETF RFC 3551, July 2003.
[RFC3711] Baugher, et al., "The Secure Real Time Transport Protocol",
IETF RFC 3711, March 2004.
[RFC4566] Handley, M., Jacobson, V. and Perkins, C., "SDP: Session
Description Protocol", IETF RFC RFC4566, July 2006.
[RFC4855] Casner, S., "Media Type Registration of RTP Payload
Formats", RFC 4855, February 2007.
[RFC5124] Ott, J. and Carrara, E., "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based
Feedback(RTP/SAVPF)", RFC 5124, February 2008.
[RFC6562] Perkins, C. and Valin, J. M., "Guidelines for the Use of
Variable Bit Rate Audio with Secure RTP", RFC 6562, March 2012.
[RFC6838] Freed, N., Klensin, J. and Hansen, T., "Media Type
Specifications and Registration Procedures", BCP 13, RFC 6838,
January 2013.
[RFC8083] Perkins, C. and V. Singh, "Multimedia Congestion Control:
Circuit Breakers for Unicast RTP Sessions", RFC 8083, January 2017.
[RFC8085] Eggert, L., Fairhurst, G. and Shepherd, G., "UDP Usage
Guidelines", RFC 8085, February 2017.
[MELP] Department of Defense Telecommunications Standard, "Analog-to-
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Digital Conversion of Voice by 2,400 Bit/Second Mixed Excitation
Linear Prediction (MELP)", MIL-STD-3005, December 1999.
[MELPE] North Atlantic Treaty Organization (NATO), "The 600 Bit/S,
1200 Bit/S and 2400 Bit/S NATO Interoperable Narrow Band Voice
Coder", STANAG No. 4591, January 2006.
[SCIP210] National Security Agency, "SCIP Signaling Plan", SCIP-210,
December 2007.
10.2 Informative References
[RFC7201] Westerlund, M. and Perkins, C., "Options for Securing RTP
Sessions", RFC 7201, April 2014.
[RFC7202] Perkins, C. and Westerlund, M., "Securing the RTP
Framework: Why RTP Does Not Mandate a Single Media Security
Solution", RFC 7202, April 2014.
Authors' Addresses
Victor Demjanenko, Ph.D.
VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202
Buffalo, NY 14228
USA
Phone: +1 716 688 4675
Email: victor.demjanenko@vocal.com
David Satterlee
VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202
Buffalo, NY 14228
USA
Phone: +1 716 688 4675
Email: david.satterlee@vocal.com
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