Subject: [MMUSIC] RECORD removed?

From: [email-masked]
Date: Mon, 21 Feb 2011 08:21:45 -0800

Sorry if this is the wrong mailing list to discuss this, but I noticed
in draft-ietf-mmusic-rfc2326bis-26 that the RECORD method has been
removed from RTSP. Is this because the recording-like functionality
has been removed from RTSP or is there another recommended mechanism
in RTSP 2.0?

I'm using RTSP to control pushing of audio and video content for live
playback on an RTSP server device. So a client connects to the RTSP
server, sets up a session, and then sends a RECORD to the server to
prepare it to receive audio and video RTP streams. The server then
plays those streams via its audio/video hardware (e.g. a TV is the
RTSP server and plays the content on its screen and speakers).

Is this a valid use of RTSP 2.0?

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From: Magnus Westerlund <[email-masked]>
Date: Mon, 21 Feb 2011 17:57:06 +0100

> Is this a valid use of RTSP 2.0?

Hi,

You are certainly on the right list.

We excluded RECORD from RTSP 2.0 because it underspecified nature, and
the lack of interest from anyone in performing the specification work
needed.

As your use case appears to be primarily a case of configuring a media
stream sink. There is no action for the server to do other than to
render what ever media it receives. Thus I would think that this can be
easily accomplished using an auto-answering SIP client in what you call
the server.

I think if one was interested in defining RECORD for RTSP 2.0 one should
start at considering what functionality are one really needing, and what
is the semantics of RECORD. This as I think your use case could be
viewed in several ways from an semantics point of view. One is to view
it as playback scenario where the server controls the client, rather
than having the client request from the server what to play.

Cheers

Magnus Westerlund

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From: [email-masked]
Date: Mon, 21 Feb 2011 12:16:24 -0800

> easily accomplished using an auto-answering SIP client in what you call

Thanks, I'll check out SIP.

My reason for starting with RTSP is that it also has several other
features I need:

- SETUP/TEARDOWN for session management. I use this for correlating
audio and video streams as well as controlling access (e.g. a device
might only support playing one audio stream at a time and I use RTSP
sessions to manage this).

- ANNOUNCE/DESCRIBE for communicating stream details (e.g. encoding
formats, RTP payload type mappings, etc.).

- GET_PARAMETER/SET_PARAMETER for things like controlling audio
volume, setting meta data, etc.

Does this seem like an appropriate use of RTSP?

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From: Magnus Westerlund <[email-masked]>
Date: Wed, 23 Feb 2011 09:06:52 +0100

> Does this seem like an appropriate use of RTSP?

Well, your semantics is using the reverse direction for what RTSP PLAY
functionality was designed for. And the RECORD semantics has some
additional things actually doing with recording, rather than controlling
far end playback.

I would say that RTSP 2.0 would need a serious consideration of the
semantics and likely some extensions to cleanly support your use case.
At the same time, I don't know what amount of extensions would be needed
in SIP case for handling the Meta data and other settings.

The question is what your goals are. Do you want a standardized solution
for performing your use case, or simply trying to capitalize on existing
implementations? IF the later than it might be possible to take parts of
a client implementation and drop it into the server side to reverse the
direction of messages. IF you want standardization I that is also
possible, but will need quite a lot of work.

Cheers

Magnus Westerlund