[AVTCORE] Magnus Westerlund's Discuss on draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)
Magnus Westerlund via Datatracker <noreply@ietf.org> Mon, 30 September 2019 14:18 UTC
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Subject: [AVTCORE] Magnus Westerlund's Discuss on draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)
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Magnus Westerlund has entered the following ballot position for draft-ietf-payload-tsvcis-03: Discuss When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: https://datatracker.ietf.org/doc/draft-ietf-payload-tsvcis/ ---------------------------------------------------------------------- DISCUSS: ---------------------------------------------------------------------- 1. Section 3.3: A TSVCIS RTP packet consists of zero or more TSVCIS coder frames (each consisting of MELPe and TSVCIS coder data) followed by zero or one MELPe comfort noise frame. The presence of a comfort noise frame can be determined by its rate code bits in its last octet. I am missing a quite important word in this paragraph. Because I assume that the frame actually are required to be consecuitive frames in time order from oldest to newest? 2. Section 4.1: Change controller: IETF Payload working group delegated from the IESG. IESG should we adjust this immediately to say IETF, although this is the currently recommended text in RFC 8088. Or are we only adjusting the working group? ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- A. Section 3.3: TSVCIS coder frames in a single RTP packet MAY be of different coder bitrates. With the exception for the variable length TSVCIS parameter frames, the coder rate bits in the trailing byte identify the contents and length as per Table 1. If I understand this correctly in an RTP payload that contain mulyiplr bit-rate frames the safest way of decoding this payload is to work from the end of the payload towards the start identifying a frame at a time. Then after having figured out how many frames actually are present, one can calculate the timestamp value for each frame. B. Section 4.4: In the Offer/Answer model [RFC3264], "bitrate" is a bidirectional parameter. Both sides MUST use a common "bitrate" value or values. The offer contains the bitrates supported by the offerer, listed in its preferred order. The answerer MAY agree to any bitrate by listing the bitrate first in the answerer response. Additionally, the answerer MAY indicate any secondary bitrate or bitrates that it supports. The initial bitrate used by both parties SHALL be the first bitrate specified in the answerer response. For example, if offerer bitrates are "2400,600" and answer bitrates are "600,2400", the initial bitrate is 600. If other bitrates are provided by the answerer, any common bitrate between the offer and answer MAY be used at any time in the future. Activation of these other common bitrates is beyond the scope of this document. I am a bit surprised to see bit-rate as bidirectional parameter here. In most use cases where RTP opperates each direction can simply express what they accept, and the media sender towards that receiver will simply provide what the receiver part has declared as acceptable. Can you please provide to me a bit more motivation why the use of bidirectional is needed? C. Section 3 and 5: Marker bit definition. The usage of the M bit SHOULD be as specified in the applicable RTP profile -- for example, [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. Section 5: A primary application of TSVCIS is for radio communications of voice conversations, and discontinuous transmissions are normal. When TSVCIS is used in an IP network, TSVCIS RTP packet transmissions may cease and resume frequently. RTP synchronization source (SSRC) sequence number gaps indicate lost packets to be filled by PLC, while abrupt loss of RTP packets indicates intended discontinuous transmissions. I would have expected this format that is clearer on its usage of DTX that it would talk about that marker bit will be = 1 after each DTX period when one no longer transmitts comfort noise only.
- [AVTCORE] Magnus Westerlund's Discuss on draft-ie… Magnus Westerlund via Datatracker
- Re: [AVTCORE] Magnus Westerlund's Discuss on draf… Barry Leiba
- Re: [AVTCORE] Magnus Westerlund's Discuss on draf… victor.demjanenko
- Re: [AVTCORE] Magnus Westerlund's Discuss on draf… Barry Leiba
- Re: [AVTCORE] Magnus Westerlund's Discuss on draf… Magnus Westerlund
- Re: [AVTCORE] Magnus Westerlund's Discuss on draf… Magnus Westerlund