Re: [AVTCORE] I-D Action: draft-ietf-avtcore-multi-party-rtt-mix-04.txt
Gunnar Hellström <gunnar.hellstrom@ghaccess.se> Mon, 01 June 2020 20:57 UTC
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From: Gunnar Hellström <gunnar.hellstrom@ghaccess.se>
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Date: Mon, 01 Jun 2020 22:57:44 +0200
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Subject: Re: [AVTCORE] I-D Action: draft-ietf-avtcore-multi-party-rtt-mix-04.txt
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I want to propose one more change in the "text/rex" packet format, that is not included in the latest draft -04. The format in the draft is not specified to be based on RFC 2198 as is the case with RFC 4103. We always have t140 as the data format in the primary and redundant data fields. So there is no need to have that configurable by the fmtp sdp attribute. It can be specified in the text/rex format. The 7 bits PT field in the data header that is now specified to contain the PT number of the t140 format can instead be used as a sequence number per source. That would make it possible to cover a functional limitation in the current specification: If there is more loss of packets than can be covered by the redundancy, it is not possible to deduct which sources were struck by the loss. The loss indication cannot be made specific to any stream from a source, but can only be made general. By introducing the sequence number per source, it gets possible to check which source was struck. The receiver needs to have a status with memory for the latest received sequence number per source. At each packet reception, the received source sequence numbers SHOULD be checked for gaps, and if a gap is detected, it can be found which sources were struck, and marks for loss can be inserted in the correct streams. It is a win-win situation. The SDP gets less complex, the loss can be decided per source and the packet format gets less complex. Can there be any situations when this does not work? Or any other reasons for why not accept this proposed change? Regards Gunnar Den 2020-06-01 kl. 17:53, skrev Gunnar Hellström: > A new version of the multi-party mixing draft for RTT is available. > > The changes are mainly in cleaning up logic and language and make the > structure of the document more clear. > > Regards > > Gunnar > > Den 2020-06-01 kl. 17:43, skrev internet-drafts@ietf.org: >> A New Internet-Draft is available from the on-line Internet-Drafts >> directories. >> This draft is a work item of the Audio/Video Transport Core >> Maintenance WG of the IETF. >> >> Title : RTP-mixer formatting of multi-party >> Real-time text >> Author : Gunnar Hellstrom >> Filename : draft-ietf-avtcore-multi-party-rtt-mix-04.txt >> Pages : 38 >> Date : 2020-06-01 >> >> Abstract: >> Real-time text mixers for multi-party sessions need to identify the >> source of each transmitted group of text so that the text can be >> presented by endpoints in suitable grouping with other text from the >> same source. >> >> Regional regulatory requirements specify provision of real-time text >> in multi-party calls. RFC 4103 mixer implementations can use >> traditional RTP functions for source identification, but the mixer >> source switching performance is limited when using the default >> transmission with redundancy. >> >> An enhancement for RFC 4103 real-time text mixing is provided in the >> present specification, suitable for a centralized conference model >> that enables source identification and efficient source switching. >> The intended use is for real-time text mixers and multi-party-aware >> participant endpoints. The mechanism builds on use of the CSRC list >> in the RTP packet and an extended packet format 'text/rex'. >> >> A capability exchange is specified so that it can be verified that a >> participant can handle the multi-party coded real-time text stream. >> The capability is indicated by the media subtype "text/rex". >> >> The document updates RFC 4102[RFC4102] and RFC 4103[RFC4103] >> >> A brief description about how a mixer can format text for the case >> when the endpoint is not multi-party aware is also provided. >> >> >> The IETF datatracker status page for this draft is: >> https://datatracker.ietf.org/doc/draft-ietf-avtcore-multi-party-rtt-mix/ >> >> There are also htmlized versions available at: >> https://tools.ietf.org/html/draft-ietf-avtcore-multi-party-rtt-mix-04 >> https://datatracker.ietf.org/doc/html/draft-ietf-avtcore-multi-party-rtt-mix-04 >> >> >> A diff from the previous version is available at: >> https://www.ietf.org/rfcdiff?url2=draft-ietf-avtcore-multi-party-rtt-mix-04 >> >> >> >> Please note that it may take a couple of minutes from the time of >> submission >> until the htmlized version and diff are available at tools.ietf.org. >> >> Internet-Drafts are also available by anonymous FTP at: >> ftp://ftp.ietf.org/internet-drafts/ >> >> >> _______________________________________________ >> Audio/Video Transport Core Maintenance >> avt@ietf.org >> https://www.ietf.org/mailman/listinfo/avt > -- Gunnar Hellström GHAccess gunnar.hellstrom@ghaccess.se
- Re: [AVTCORE] I-D Action: draft-ietf-avtcore-mult… Gunnar Hellström
- [AVTCORE] I-D Action: draft-ietf-avtcore-multi-pa… internet-drafts
- Re: [AVTCORE] I-D Action: draft-ietf-avtcore-mult… Gunnar Hellström