Subject: Re: [MMUSIC] Relative URLs in RTP-Info field

From: Aravind Narasimhan <[email-masked]>
Date: Wed, 05 Mar 2003 08:13:14 -0800

Aaron Colwell wrote:

>Thank you for the clarification. I was somewhat expecting that answer, but
>I just wanted to make sure.
>
>One other thing that I'd like to have clarified is that if absolute URLs
>are returned that they match what was sent in the SETUP request for that
>stream. I've run into a case where a server will return me an IP address
>in the hostname part of the URL instead of the hostname that I specified.
>It is things like this that make matching SETUP URLs with RTP-Info
>information not very easy. I'd like to not have to use heuristic methods
>for dealing with these types of situations. Perhaps the clarification for
>RTP-Info URLs should be something like
>
>"Any relative URL SHALL use the request URL as base URL. The resulting
> URL must match the URL used to SETUP that stream.
>
I'm not sure exactly what it means to say "the resulting URL must match 
the URL used to SETUP that stream."  In the case below, for example, the 
SETUP URLs are different than the PLAY URL.

OPTIONS rtsp://foo.com
SETUP rtsp://foo.com/audio.3gp/trackID=1
SETUP response
SETUP rtsp://foo.com/video.3gp/trackID=1
SETUP response
PLAY rtsp://foo.com/movie
PLAY response
RTP-Info: url=audio.3gp/trackID=1;seq=0;rtptime=0,
url=video.3gp/trackID=1;seq=234;rtptime=23487

The resulting full url is rtsp://foo.com/movie/audio.3gp/trackID=1 and rtsp://foo.com/movie/video.3gp/trackID=1, which are not the same as the SETUP urls.

> If an absolute URL is
> specified, it MUST match the URL used to SETUP that stream."
>
I think we need to clearer on the exact wording and probably provide a 
good example (similar to what's been give on this alias).

Aravind

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---

From: Magnus Westerlund <[email-masked]>
Date: Wed, 05 Mar 2003 17:24:58 +0100

Hi Aravind,

You are making a mistake here. You are not following the correct rules 
for how to resolve relative URLs.
See RFC 2396 for these rules.

>
> The resulting full url is rtsp://foo.com/movie/audio.3gp/trackID=1 and 
> rtsp://foo.com/movie/video.3gp/trackID=1, which are not the same as 
> the SETUP urls.

The error you made here is that you did not remove all that is after the 
last "/". The base URL is "rtsp://foo.com/movie" however when resolving 
this you take the part upto and including the last "/", i.e, 
"rtsp://foo.com/". To this you add the relative URL resulting in:
rtsp://foo.com/audio.3gp/trackID=1
rtsp://foo.com/video.3gp/trackID=1

> good example (similar to what's been give on this alias). 

Sure, improving the text is always good. Do you have any proposal what 
would be clearer?

Best Regards.

Magnus Westerlund 

Multimedia Technologies, Ericsson Research ERA/TVA/A
----------------------------------------------------------------------
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S-164 80 Stockholm, Sweden | mailto: [email-masked]

---

From: Aravind Narasimhan <[email-masked]>
Date: Wed, 05 Mar 2003 08:38:27 -0800

>
>
>>
>> The resulting full url is rtsp://foo.com/movie/audio.3gp/trackID=1 
>> and rtsp://foo.com/movie/video.3gp/trackID=1, which are not the same 
>> as the SETUP urls.
>
>
> The error you made here is that you did not remove all that is after 
> the last "/". The base URL is "rtsp://foo.com/movie" however when 
> resolving this you take the part upto and including the last "/", i.e, 

oh yeah. ..  my bad.  We ran into a similar problem before for the same 
reason. .   so ignore my comment.

>> I think we need to clearer on the exact wording and probably provide 
>> a good example (similar to what's been give on this alias
>

I'll look through the current wording as well as our current email 
thread on this and propose some new wording within the next week.

Aravind