Magnus Westerlund <magnus.westerlund@ericsson.com> writes:
You are correct it is not SDP that limits the usage, the question is what the right type is. 3GPP Timed text is clearly text and it is displayed as lines. However it also has connections to video by being specified to placed as an overlay in a specific part of the video display.
Ummm. So anything that can be eventually displayed (on a monitor or other screen, since text could be displayed on a text-only display or beeper, etc) is "video"? This really, really rubs me the wrong way. It just feels "wrong". Now, it can be under anything. But what's the _purpose_ and effect? Often, applications using SDP limit the number of streams of a type (1 audio, 1 video, etc). Now, they could relax that, but it starts adding complexity to the negotiations ("1 video but 2 if one (and only one) of the streams selects a text payload type"). It makes sense for it to be video if it's intended to be in the same stream as "real" video as an alternate payload type (as an overlay on video). Maybe that's the case, in which case I partly withdraw my objection.
In addition certain of the modifiers create video-like modifications of the text strings. Especially the karaoke modifier that repaint the characters with a time dependent speed.
I wouldn't consider that "video-like". Non-static, but not video-like.
So it is text, but with a twist. My opinion is that this still is text and many streams will be possible to display on a text only device. You can could in fact make a stock ticker that receives this format.
Stock ticker, "beeper", IM-specific device, cell SMS messages, scrolling-text displays in stores, etc, etc. Note: I really haven't been following this, so take my comments with a block of salt. -- Randell Jesup, Worldgate Communications, ex-Scala, ex-Amiga OS team rjesup@wgate.com