INTERNET-DRAFT Victor Demjanenko David Satterlee Intended Status: Experimental VOCAL Technologies, Ltd. Expires: March 25, 2016 September 22, 2015 RTP Payload Format for MELPe Codec draft-demjanenko-payload-melpe-04 Status of this Memo Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Abstract This document describes the RTP payload format for the Mixed Excitation Linear Prediction Enhanced (MELPe) 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. All three different speech encoding rates and sample frames sizes are included. Comfort noise procedures and packet loss concealment are detailed. Also, within the document there are included necessary details for the use of MELP with SDP. Demjanenko, Satterlee Expires March 25, 2016 [Page 1] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 . . . . . . . . . . . . . . 5 3.1.2 1200 bps Bitstream Structure . . . . . . . . . . . . . . 8 3.1.3 600 bps Bitstream Structure . . . . . . . . . . . . . . 11 3.2 MELPe Comfort Noise Bitstream Definition . . . . . . . . . 14 3.3 Multiple MELPe frames in a RTP packet . . . . . . . . . . . 16 3.4 Congestion Control Considerations . . . . . . . . . . . . . 18 4 Payload Format Parameters . . . . . . . . . . . . . . . . . . . 18 4.1 Media Type Definition . . . . . . . . . . . . . . . . . . . 18 4.2 Mapping to SDP . . . . . . . . . . . . . . . . . . . . . . 20 5 Discontinious Transmission . . . . . . . . . . . . . . . . . . 22 6 Packet Loss Concealment . . . . . . . . . . . . . . . . . . . . 23 7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 24 8 Security Considerations . . . . . . . . . . . . . . . . . . . . 24 9 RFC Editor Considerations . . . . . . . . . . . . . . . . . . . 24 10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 24 10.1 Normative References . . . . . . . . . . . . . . . . . . . 24 10.2 Informative References . . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26 Demjanenko, Satterlee Expires March 25, 2016 [Page 2] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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]. 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]. 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 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 Demjanenko, Satterlee Expires March 25, 2016 [Page 3] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 is recommended to follow 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 the figure below. No additional header specific to this payload format is required. This format is intended for the situations where the sender and the receiver send one or more codec data frames per packet. The RTP packet looks as follows: 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 Demjanenko, Satterlee Expires March 25, 2016 [Page 4] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 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. 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 | Demjanenko, Satterlee Expires March 25, 2016 [Page 5] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 | 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 | | 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 | Demjanenko, Satterlee Expires March 25, 2016 [Page 6] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 | 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. 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 | +------+------+------+------+------+------+------+------+ Demjanenko, Satterlee Expires March 25, 2016 [Page 7] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 | +--------+-------------+-------------+ | 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 | Demjanenko, Satterlee Expires March 25, 2016 [Page 8] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 +--------+-------------+-------------+ | 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 | | | 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 | | Demjanenko, Satterlee Expires March 25, 2016 [Page 9] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 | 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. 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 | +------+------+------+------+------+------+------+------+ Demjanenko, Satterlee Expires March 25, 2016 [Page 10] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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) | +--------+-------------+-------------+-------------+ | 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) | Demjanenko, Satterlee Expires March 25, 2016 [Page 11] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 | 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) | | 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) | Demjanenko, Satterlee Expires March 25, 2016 [Page 12] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 | 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) | +--------+-------------+-------------+-------------+ | 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) | +--------+-------------+-------------+-------------+ Demjanenko, Satterlee Expires March 25, 2016 [Page 13] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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. 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. +-------------------------------------+----------------+ | MELPe Parameter | Value | +-------------------------------------+----------------+ Demjanenko, Satterlee Expires March 25, 2016 [Page 14] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 | 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 value shall be the respective parameters from the vocoder frame. It is recommended 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 required, the following bit order is used for comfort noise frames. +--------+-------------+ | 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 | Demjanenko, Satterlee Expires March 25, 2016 [Page 15] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 +--------+-------------+ | 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, 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 may be required to reduce the packet rate. 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 Demjanenko, Satterlee Expires March 25, 2016 [Page 16] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 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 may 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. Demjanenko, Satterlee Expires March 25, 2016 [Page 17] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 3.4 Congestion Control Considerations Congestion control for RTP SHALL be used in accordance with RFC 3550 [RFC3550], and with any applicable RTP profile; e.g., RFC 3551 [RFC3551]. An additional requirement if best-effort service is being used is: users of this payload format MUST monitor packet loss to ensure that the packet loss rate is within acceptable parameters. Circuit Breakers [I-D.ietf-avtcore-rtp-circuit-breakers] is an update to RTP [RFC3550] that defines criteria for when one is required to stop sending RTP Packet Streams. The circuit breakers is to be implemented and followed. 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]. 4.1 Media Type Definition Type names: MELP, MELP2400, MELP1200, and MELP600 Subtype name: N/A Required parameters: N/A Optional parameters: ptime, maxptime, bitrate Encoding considerations: This media type is framed and binary, see section 4.8 in RFC6838 [RFC6838]. Security considerations: Please see security consideration in RFCXXXX Interoperability considerations: Demjanenko, Satterlee Expires March 25, 2016 [Page 18] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 Restrictions on usage: Demjanenko, Satterlee Expires March 25, 2016 [Page 19] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 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 MIME media type specification has a specific mapping to fields in the Session Description Protocol (SDP) [RFC2327], 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 MIME type ("audio") goes in SDP "m=" as the media name. o The MIME 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 directly from the MIME media type string as "bitrate=value" or "bitrate=value1,value2" or "bitrate=value1,value2,value3". When conveying information by SDP, the encoding name SHALL be "MELP" (the same as the MIME 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 Demjanenko, Satterlee Expires March 25, 2016 [Page 20] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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. A remote MELPe encoder SHALL receive "bitrate" parameter in the SDP "a=fmtp" attribute by copying them directly from the MIME media type string as a semicolon separated with parameter=value, where parameter is "bitrate", and 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 For streaming media, the "bitrate" parameter specifes the possible bit rates used by the sender. 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 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. Demjanenko, Satterlee Expires March 25, 2016 [Page 21] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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. 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.). When SDP is used for broadcast MELPe audio, 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 Note that the payload format (encoding) names are commonly shown in upper case. MIME 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 The value for "packet time" and "maximum packet time" parameters of the "ptime" and "maxptime" SDP attributes respectively, 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 may be used as long as they are properly rounded. 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 Demjanenko, Satterlee Expires March 25, 2016 [Page 22] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 may utilize any of the errored encodings of a non-voiced frame as identified in Table 1 of [MELPE]. For the sake of simplicity it is recommended 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. Demjanenko, Satterlee Expires March 25, 2016 [Page 23] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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 [RFC4585], 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 its media 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. 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 [I-D.ietf-avtcore-rtp-circuit-breakers] Perkins, C. and V. Singh, "Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions", draft-ietf-avtcore-rtp-circuit-breakers-10 (work in progress), March 2015. Demjanenko, Satterlee Expires March 25, 2016 [Page 24] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2327] M. Handley and V. Jacobson, "SDP: Session Description Protocol", IETF RFC 2327, April 1998 [RFC2736] M. Handley and C. Perkins, "Guidelines for Writers of RTP Payload Format Specifications", BCP 36, RFC 2736, December 1999. [RFC3264] J. Rosenberg, H. Schulzrinne, "An Offer/Answer Model with the Session Description Protocol (SDP)" IETF RFC 3264, June 2002. [RFC3550] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", IETF RFC 3550, July 2003. [RFC3551] H. Schulzrinne, S. Casner, "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. [RFC4855] Casner, S., "Media Type Registration of RTP Payload Formats", RFC 4855, February 2007. [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback(RTP/SAVPF)", RFC 5124, February 2008. [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, January 2013. [RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP Sessions", RFC 7201, April 2014. [RFC7202] Perkins, C. and M. Westerlund, "Securing the RTP Framework: Why RTP Does Not Mandate a Single Media Security Solution", RFC 7202, April 2014. 10.2 Informative References [MELP] Department of Defense Telecommunications Standard, "Analog-to- 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, Demjanenko, Satterlee Expires March 25, 2016 [Page 25] INTERNET DRAFT RTP Payload Format for the MELPe CodecSeptember 22, 2015 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. 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 Demjanenko, Satterlee Expires March 25, 2016 [Page 26]