Subject: MUTE in RTSP

From: Eric Fleischman <[email-masked]>
Date: Fri, 18 Apr 1997 09:41:57 -0700

The Sept 26th version of the RTSP spec introduced the much-needed
concept of "presentation" which was defined (see section 1.3) as "a set
of one or more streams which the server allows the client to manipulate
together." These streams are treated as a "unit", a "multimedia bundle"
so-to-speak.

The spec also preserves the concept of permitting separate media streams
(which have not been defined into a presentation) to be controlled from
the same source. That is, a set of multimedia streams may be formed into
a logical session via registration/announcement facilities. The user is
freely able to address and modify each of these streams within the
constraints supported by RTSP.

I believe that these two different control mechanisms provide us with
the necessary insight to agree to what MUTE should mean in RTSP.

In the first instance, all media streams are treated as a unit and are
transparently manipulated together. In most/many cases, "presentations"
will be the product of content creators who have designed these streams
"off line" to function as that unit to create the intended multimedia
experience. A MUTE, in this context, would introduce an orthogonal
concept of providing independent control for one of those streams in the
"multimedia bundle". This is hostile to the basic underlying philosophy
of what a "presentation" actually is. MUTE is totally inappropriate
within a "presentation" since it wars with the "core underlying
philosophy" of what a "presentation" actually is.

In the second instance, RTSP provides for the independent control of
multiple media streams which the user (via the intermediate
registration/announcement facilities) has orchestrated into a single
logical session. RTSP has already provided the user with the ability to
do a MUTE within this context by permitting him/her to PAUSE the audio
stream and at a subsequent time to PLAY with Offset that same stream. A
Mute in this instance, therefore, is merely a "simplification" to the
PAUSE...PLAY with Offset sequence. I have no objection to a MUTE if it
is solely targeted to this (non-presentation) environment since it
automates what the "Offset" should be in the "Play with Offset" part of
the sequence. More importantly, a MUTE in this context is fully
consistent with the "underlying philosophies" of such logical sessions.

---

From: Karl Auerbach <[email-masked]>
Date: Fri, 18 Apr 1997 12:44:38 -0700 (PDT)

> ... A MUTE, in this context, would introduce an orthogonal

???!!  Do you mean that if I'm watching my network TV and that I stop the
sound from playing while I answer the telephone that I'm doing something
"totally inappropriate"?  I'm in a lot of trouble then. 

If the person in control of a group of media streams (a "presentation" 
perhaps) wants to say "don't send the audio portion for a while, but keep
the clock ticking" and the server honors that request, then I say hurray! 
It's what the user wants and its good for the network. 

			--karl--