[vlc] Re: Streaming MP3 over RTP (Helix DNA server)

[Ross Finlayson]

>I am using Helix DNA server in my system to stream out MP3 Files as RTP 
>(over UDP) payload and with RTSP as the Control Protocol.
>
>On the client side, I am running VLC Player. I captured the RTP packets 
>that starts flowing from the server and have observed that the Helix 
>Server is sending only the Header+CRC+Side Information of the MP3 frame 
>intact but sending the Main Data of the frame across the frames. i.e., the 
>Main Data of 1 st frame may be available in the future frames.
>
>I like to know how VLC player is handling the packet loss ?  What will 
>happen if we happen to loose one RTP packet in the stream ? How to 
>reconstruct the MP3 frames?

Balaji,

You have identified a known problem with RFC 2250-compliant MP3/RTP 
streaming: The use of a 'bit reservoir' within MP3 frames means that - when 
packets get lost - the reconstructed MP3 data will contain audio artifacts.

The solution is to use the newer "audio/mpa-robust" RTP payload format 
defined by RFC 3119: see <http://www.live.com/rtp-mp3/rtp-mp3.txt> and 
<http://www.live.com/rtp-mp3/>.

I don't know whether "Helix DNA server" supports this; however, the 
LIVE.COM "testMP3Streamer" (multicast) and "testOnDemandRTSPServer" 
(unicast) test programs (see <http://www.live.com/liveMedia/>) do support 
this, as an option.  (You will need to uncomment the line
         #define STREAM_USING_ADUS 1
and recompile.)  I suggest that you use one of these applications instead 
of "Helix DNA server".

And, of course, the VLC media player client will handle either payload format.


	Ross Finlayson
	LIVE.COM
	<http://www.live.com/>

-- 
This is the vlc mailing-list, see http://www.videolan.org/vlc/
To unsubscribe, please read http://www.videolan.org/support/lists.html