[vlc-devel] Re: Using vlc as a relay source for Darwin Streaming Server.

[Derk-Jan Hartman]

Mostly applied in https://trac.videolan.org/vlc/changeset/14552
Note that the code had changed since 0.8.2, so I had to adapt the  
patch. I'm not sure if it's 100% correct for you know. I would  
appreciate it if you could test it and let us know your results.

DJ

On 25-feb-2006, at 12:36, Leonardo wrote:

> As well known, vlc can operate as an encoder for a Darwin Streaming  
> Server
> (DSS) by creating an sdp file, copying it to /usr/local/movies and  
> starting to
> send media flows with the same options used for sdp creation.
> DSS will happily reflect the flows to every requesting client; just  
> make sure
> to use the "ttl=" option in the #rtp module for sdp creation.
>
> Troubles arise trying to use vlc as an "Origin" in the frame work  
> of the
> OpenCDN (http://labtel.ing.uniroma1.it/opencdn/) project.
> In that case, DSS is configured as a relay and, according to a "pull"
> paradigm, it needs to act as an RTSP client towards vlc in order to  
> make a
> remote stream locally available to clients.
> In that way, the sdp metadata is tranferred to DSS during the RTSP  
> negotiation
> phase, and no manual copy of the sdp file is needed...the only  
> problem is that
> DSS seems to be unable to complete an RTSP request with vlc  
> configured as an
> RTSP server !!!
>
> After some thought a difference has been found between the headers  
> format of
> the RTSP DESCRIBE answer returned by vlc and the one returned by DSS.
> As vlc is perfectly able to complete an RTSP request to DSS while  
> DSS cannot
> do the same with vlc configured as an RTSP server the  
> incompatibility could
> be on the vlc side, so the need to dig into the code.
>
> In the following the formal description of the problem and its  
> solution.
>
> 2 computers:
> - PC#1 ( call it vlc_pc): runs vlc-0.8.2 compiled from sources;
> - PC#2 (call it darwin_pc): runs Darwin Streaming Server.
> Goal:
> - use vlc on PC#1 with the following command to generate the sdp of a
>   file/live-content and make it available to DSS via the rtsp  
> protocol:
> [root at vlc_pc]# vlc -vvv my_file.mp4 --sout
> '#rtp{port=1234,ttl=8,sdp=rtsp://vlc_pc_ip_addr/test_vlc.sdp}'
> - use Darwin on PC#2 as a relay with the following configuration:
> Relay Name: darwin_relay
> Status:  Enabled  # AFTER vlc STARTED TO STREAM.
> Source Settings
>  Source Hostname or IP Address: vlc_pc_ip_addr  # LOOK AT THE rtp  
> MODULE IN THE VLC COMMAND.
>  Mount Point: test_vlc.sdp  # LOOK AT THE rtp MODULE IN THE VLC  
> COMMAND.
>  Request incoming stream
> Destination Settings (1 of 1)
>  Hostname or IP Address: 127.0.0.1
>  Announced UDP
>  Mount Point: test_darwin.sdp
>
> It works having recompiled vlc after the following changes in
> vlc-0.8.2/modules/stream_out/rtp.c:
> - ROW 736:
> i_size += strlen( "a=control:*/trackid=*\r\n" ) + strlen( p_sys- 
> >psz_rtsp_control ) + 10; --->
> i_size += strlen( "a=control:*/trackID=*\r\n" ) + strlen(p_sys- 
> >psz_rtsp_control) + 10;
> - ROW 789:
> p += sprintf( p, "a=control:%s/trackid=%d\r\n", p_sys- 
> >psz_rtsp_control, i ); --->
> p += sprintf( p, "a=control:trackID=%d\r\n", i );
> - ROW 1033:
> sprintf( psz_urlc, "%s/trackid=%d", p_sys->psz_rtsp_path, p_sys- 
> >i_es ); --->
> sprintf( psz_urlc, "%s/trackID=%d", p_sys->psz_rtsp_path,p_sys- 
> >i_es );
>
> The problem was in the a=control fields of the sdp:
> - vlc generates the fields:
> a=control:rtsp://vlc_pc:554/test.sdp/trackid=0
> a=control:rtsp://vlc_pc:554/test.sdp/trackid=1
> - while Darwin expects the fields to be:
> a=control:trackID=0
> a=control:trackID=1
>
> To use vlc with telnet interface it's necessary to make similar  
> changes in
> vlc-0.8.2/modules/misc/rtsp.c too:
> - ROWS 361-362:
> asprintf( &psz_urlc, "%s/trackid=%d", p_media->psz_rtsp_path,  
> p_media->i_es ); --->
> asprintf( &psz_urlc, "%s/trackID=%d", p_media->psz_rtsp_path,  
> p_media->i_es );
> - ROWS 985-986:
> i_size += strlen( "a=control:*/trackid=*\r\n" ) + strlen( p_media- 
> >psz_rtsp_control ) + 10; --->
> i_size += strlen( "a=control:*/trackID=*\r\n" ) + strlen( p_media- 
> >psz_rtsp_control ) + 10;
> - ROWS 1042-1043:
> p += sprintf( p, "a=control:%s/trackid=%d\r\n", p_media- 
> >psz_rtsp_control, i ); --->
> p += sprintf( p, "a=control:trackID=%d\r\n", i);
>
> Attached You can find a diff file with all the changes.
>
> The above mentioned changes don't affect regular vlc to vlc  
> operations.
>
> Please, can You insert those changes in one of the next daily code  
> snapshots?
> If You can't, there's a reason ?
> That would be very important to us because We are trying to  
> integrate vlc
> within the OpenCDN project frame work.
> <diff_vlc>

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