Subject: [AVT] Describing Dynamic payloads using RTCP?

From: Nicholas J Humfrey <[email-masked]>
Date: Tue, 8 May 2007 13:06:52 +0100

Hi,

Is it possible to describe dynamic RTP payloads using RTCP? ie.  
sending a SDP style rtpmap line in an RTCP packet:

rtpmap:100 L16/22050/2

nick.

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: Colin Perkins <[email-masked]>
Date: Tue, 8 May 2007 13:37:10 +0100

> sending a SDP style rtpmap line in an RTCP packet:

No.

Colin

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From: Nicholas J Humfrey <[email-masked]>
Date: Tue, 8 May 2007 13:59:22 +0100

Is it a bad idea? It would be very handy for self describing audio- 
only streams.

While I am not a big fan of VLC's udp:// 'MRL's, I can definitely see  
a benefit for being able to simply pass a URL for an audio broadcast as:

rtp://multicast.surgeradio.co.uk:5004/

And the client picking up the rtpmap and fmtp information in-band.

I don't really have anything against SDP... it just makes simple  
applications a bit more complex...

nick.

On 8 May 2007, at 13:37, Colin Perkins wrote:

>> rtpmap:100 audio/L16/22050/2
>
> No.
>
> Colin

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From: Luca Barbato <[email-masked]>
Date: Tue, 08 May 2007 17:26:48 +0200

Nicholas J Humfrey wrote:
> Is it a bad idea?

Yes

> It would be very handy for self describing audio-only streams.

I don't see the point

> 
> While I am not a big fan of VLC's udp:// 'MRL's, I can definitely see a
> benefit for being able to simply pass a URL for an audio broadcast as:
> 

O_O

> applications a bit more complex...

if you have an rtsp library with a more or less decent sdp parser you
won't care that much about that... (otherwise you could just use a
custom simplified stack of protocols...)

lu

-- 

Luca Barbato

Gentoo/linux Gentoo/PPC
http://dev.gentoo.org/~lu_zero

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From: Nicholas J Humfrey <[email-masked]>
Date: Tue, 8 May 2007 16:55:04 +0100

> Yes

Heh :) Just an idea!

>> It would be very handy for self describing audio-only streams.

The point is keeping things lightweight. And let the client know what  
they are receiving without having to pass an SDP description of the  
stream from the broadcaster to the receiver out-of-band.

> If you have an RTSP library with a more or less decent SDP parser you

So I am doing RTP over multicast and having an RTSP server seems a  
bit excessive. Although perhaps a lightweight RTSP announcer isn't so  
complicated...

Using RTSP/SDP with a GUI works pretty well, but one the command-line  
there start being a hell of a lot of parameters you have to enter,  
when all you want to do is shove out the stream and start listening...

I guess an alternative would be to just host the SDP file on an HTTP  
server, but it just seems more complicated than it needs to be...

nick.

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From: Colin Perkins <[email-masked]>
Date: Tue, 8 May 2007 17:17:06 +0100

On 8 May 2007, at 16:55, Nicholas J Humfrey wrote:
...
> bit excessive. Although perhaps a lightweight RTSP announcer isn't  
> so complicated...
>
> Using RTSP/SDP with a GUI works pretty well, but one the command- 
> line there start being a hell of a lot of parameters you have to  
> enter, when all you want to do is shove out the stream and start  
> listening...
>
> I guess an alternative would be to just host the SDP file on an  
> HTTP server, but it just seems more complicated than it needs to be...

That's a pretty good solution. Or multicast the SDP file (as the old  
sdr tool did, see RFC 2974 or http://www-mice.cs.ucl.ac.uk/multimedia/ 
software/sdr/)

Colin