[vlc] Re: VLC MPEG2 streaming reception

[Derk-Jan Hartman]

On 16 feb 2005, at 14:12, Robert.Smith at ses-astra.com wrote:
> Hi all,
>
> Here is some additional information to my previous email:
>
>> The interesting thing here is that when I stream this new file using 
>> vlc
>> (vlc -vvv --extraintf logger axis-es-windows-mplayer.mpg --loop --sout
>> #rtp{dst=228.96.1.1,sdp=file://guide5.sdp} ), I can receive it fine 
>> using
>> mplayer (mplayer sdp://guide5.sdp) but if i try to receive it using 
>> vlc
>> (vlc -vvv --extraintf logger udp:@228.96.1.1) then I see video 
>> corruption.
>
> The original file (axis-es-windows-mplayer.mpg) contains an dump of an 
> RTP
> stream containing an MEPG-2 elementary video stream. Obviously if I 
> try to
> receive it as UDP instead of RTP, vlc displays the stream incorrectly. 
> I am
> actually surprised I see any picture at all.

Why don't you try to open it trough the sdp file? VLC can open SDP 
files just as well as mplayer.

> If I try the reception using the command "vlc rtp:@28.96.1.1:1236" 
> then I
> have the same behaviour as with the SDP file, namely the log output 
> shows
> "ps warning: garbage at input" messages. The video corruption problem 
> is
> therefore a "brain corruption" problem on my part.

well two things. if this is ES, and it's truly an RTP stream (ergo no 
RTSP setup), then VLC does autodetection, and i know it can be hard to 
do autodetection reliably on ES streams... Perhaps
>


> I don't understand why the ES and SDP modules are discarded. Surely 
> they
> should be used in this case? Is there a way to force vlc to use the 
> "ES"
> demux module instead of PS?

I think this is caused mostly because you mess up UDP, RTP, RTSP and 
SDP and what each of them does.

> BTW, while I was testing, I ran across a couple of anomalies:
>
> 1. VLC seems to interpret an SDP file containing a unicast destination
> incorrectly
>
> If I create an RTP stream using the command
> "vlc axis-es-linux-mplayer.mpg --sout
> #rtp{dst=228.96.1.1,sdp=file://guide5.sdp}"
> the SDP file looks like this:
> v=0
> o=- 54114853253 1 IN IP4 127.0.0.1
> s=NONE
> t=0 0
> a=tool:vlc 0.8.2-svn-20050215
> c=IN IP4 228.96.1.1/0
> m=video 10000 RTP/AVP 32
> a=rtpmap:32 MPV/90000
> and the player log file looks like this:
> main debug: adding playlist item `NONE' ( rtp://@228.96.1.1:10000 )
> The player receives the data.
>
> If I create the same stream with a unicast destination
> "vlc axis-es-linux-mplayer.mpg --sout
> #rtp{dst=10.232.31.1,sdp=file://guide5.sdp}"
> the SDP file looks like this
> v=0
> o=- 54458172939 1 IN IP4 127.0.0.1
> s=NONE
> t=0 0
> a=tool:vlc 0.8.2-svn-20050215
> c=IN IP4 10.232.31.1/0
> m=video 10000 RTP/AVP 32 a=rtpmap:32 MPV/90000
> and the player log file looks like this:
> main debug: adding playlist item `NONE' ( rtp://10.232.31.1:10000 )
>
> The missing "@" causes the player to interpret this as a stream from 
> server
> 10.232.31.1 port 10000 to the local port 1234 (default), and the player
> receives no data. It seems the player does not read the SDP file for
> unicast streams correctly.

no it doesn't. the playlistitem looks correct to me. receive from 
10.232.31.1:10000
The @ should be missing, since it explicitly denounces a multicast 
address.

> 2. "vlc axis-es-linux-mplayer.mpg --sout
> #rtp{dst=10.232.31.1,port=10000,sdp=file://guide5.sdp}" creates a 
> unicast
> stream with UDP destination port 1236, but
> "vlc axis-es-linux-mplayer.mpg --sout
> #rtp{dst=10.232.31.1,port-video=10000,sdp=file://guide5.sdp}" creates a
> unicast stream with UDP destination port 10000.

i think this is a RTSP vs. RTP issue.....

> I would expect both commands to have the same effect as the input 
> stream is
> a single elementary video stream.

with RTSP it's not. :)

DJ
---
Universiteit Twente
Derk-Jan Hartman (d.hartman at student.utwente dot nl)
http://home.student.utwente.nl/d.hartman

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