SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03
Gunnar Hellstrom <gunnar.hellstrom@omnitor.se> Thu, 06 July 2006 13:20 UTC
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From: Gunnar Hellstrom <gunnar.hellstrom@omnitor.se>
To: Gunnar Hellstrom <gunnar.hellstrom@omnitor.se>, Colin Perkins <csp@csperkins.org>
Subject: SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03
Date: Thu, 06 Jul 2006 14:19:58 +0100
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Cc: 'Cullen Jennings' <fluffy@cisco.com>, 'Gonzalo Camarillo' <Gonzalo.Camarillo@ericsson.com>, MMusic <mmusic@ietf.org>
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This is a new effort to describe the "txp" attribute for the sdp-media-content draft. My understanding is that the described use of the txp attribute is totally in alignment with the aims of sdp-media-content. It does not influence negotiation, it is just used for indication to the receiving user and possibly direction of the media stream. Current text: txp: This indicates that the media stream is originated from a textphone, and it requires special behavior from the receiving application. A typical use case for this is a connection where one endpoint is an analog textphone of a kind that cannot handle two-way simultaneous text communication, and the other one is a native IP based real time text capable terminal. The human users normally need to apply formal turn-taking habits, and need to figure out to what extent it is possible to interrupt the other party if the need arises. New proposal: txp: This indicates that the media stream is originated from a textphone with restricted presentation capabilities. A typical use case for this is a connection between a gateway and an IP terminal capable of handling real-time text. The gateway gives the "txp" indication when its connection with textphone only can transmit the text medium one way at a time. In the audio media it indicates that a textphone is connected and may take turns on using real-time text alternating with audio on the connection because of the limitation in textphone presentation capabilities. Variations of the presentation limitations exist. Not all of them are detectable. Therefore the IP session should be set up for full duplex simultaneous operation, but an indication provided in the user interface making the IP terminal user aware of the situation. A possible such indication can be to direct the real-time text conversation to one common window for both text communication directions instead of the traditional split in one window per call participant. The indication is also supposed to make the user aware of that traditional turntaking habits from PSTN text telephony may need to be applied. For audio users the indication should mean be careful and not try to use voice and text simultaneously but leave time for mode switching in the limited textphone end. More about requirements on communication with textphones through gateways can be read in RFC 2804, section 11.2.4 [xx], in ITU-T H.248.2 [xy], and in ETSI EG 202 320 [xz]. These references also give more background to the variations in presentation capabilities of various textphones. Gunnar ---------------------------------------------------------------------------- - Gunnar Hellstrom, Omnitor gunnar.hellstrom@omnitor.se Mob: +46 708 204 288 Phone: +46 8 556 002 03 www.omnitor.se -----Ursprungligt meddelande----- Fran: Gunnar Hellstrom [mailto:gunnar.hellstrom@omnitor.se] Skickat: den 5 juli 2006 22:41 Till: Colin Perkins Kopia: 'Cullen Jennings'; 'Gonzalo Camarillo'; MMusic Amne: Re: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Colin, Cullen and all, We have had a brief discussion about the "txp" attribute for the media-content parameter. I want to bring this discussion to the list. We have been asked to provide a more clear definition of what content:"txp" means. During these efforts, Colin and Cullen have started to question if it was right to include the "txp" attribute in this draft. They see some difference in type of the "txp" attribute from the other attributes in the draft. I have not seen that difference. By the end of section 5, there is a statement "All of these values can be used with any media type." We have specified "txp" so far mainly to be used together with the text medium specification. But we can define it to have meaning also for audio. It would then mean that audio contents is intermittently used and takes turns with text contents. The party signaling this attribute is likely a PSTN gateway. Between the gateway and the endpoint receiving the indication there is no strict restriction on the media. It is rather how their contents is used that is specified. Many of the other attributes are also easiest foreseable for one specific medium. sl for sign lanuage is easiest foreseeable added to the video medium. slides is easiest to foresee for the image medium. speaker is said to be video related. Thus there is no strict rule that an attribute must be valid for many media. You say that the "txp" attribute influences media negotiation when the draft says that media-content attributes should not. I cannot see that it influences media negotiation more than any other media-content attribute. The "sl" ( Sign language ) attribute may lead to some terminals avoiding to connect this medium because the user is not interested, while others can be interested to define their terminals to always negotiate the "sl" video and put it in a good viewing position. Same with "alt". On a small terminal you may preset the terminal to not show the stream with the "alt" media-content attribute. Conclusion, "txp" is an attribute of similar type as most other media-content attributes and suits well in the media-contents specification. It just needs a further elaborated description in the draft. I will have a try shortly to create that. Gunnar ---------------------------------------------------------------------------- - Gunnar Hellstrom, Omnitor gunnar.hellstrom@omnitor.se Mob: +46 708 204 288 Phone: +46 8 556 002 03 www.omnitor.se -----Ursprungligt meddelande----- Fran: Colin Perkins [mailto:csp@csperkins.org] Skickat: den 5 juli 2006 20:16 Till: Gunnar Hellstrom Kopia: Arnoud van Wijk; 'Cullen Jennings'; 'Gonzalo Camarillo'; 'Jani Hautakorpi ((JO/LMF))' Amne: Re: SV: SV: SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 On 5 Jul 2006, at 19:10, Gunnar Hellstrom wrote: > Is it OK for you if we copy this thread to the list and continue > there? If you wish. > Firstly, I saw a need to declare real-time text capability already > on the > session level. Therefore I suggested use of the Contact:;text > and there we can also use Contact;:duplex="half" as a general > indicator. > > There were cases when text medium is not declared from the > beginning, but > the capability must be declared. So, for that situation I saw no > way to use > the media-content parameter. > > I think I am satisfied with these. > > But the media-content="txp" parameter was already on its way to be > created, > so I recommended use of it too. > > It is very similar in meaning with "user-floor" as we have > discussed. A > typical media-content attribute as I see it. A quite soft indicator > that > mainly users may need to consider. Similar to the other attribute > values. > What is the problem? The "txp" media-content label is media format specific, defines some attributes of the device, and your proposal for its use impacts the media negotiation. The other content label attributes are both media format and device independent, and are ignored during media negotiation. Colin _______________________________________________ mmusic mailing list mmusic@ietf.org https://www1.ietf.org/mailman/listinfo/mmusic _______________________________________________ mmusic mailing list mmusic@ietf.org https://www1.ietf.org/mailman/listinfo/mmusic
- Re: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Gunnar Hellstrom
- SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Gunnar Hellstrom
- Re: SV: [MMUSIC] Re: ietf-mmusic-sdp-media-conten… Colin Perkins