[vlc] Re: How is AVC (x264) mapped onto IP packets?

[Ross Finlayson]

>I'm trying to examine how VLC maps AVC into an IP packet. Is the nexy
>statement correct:
>
>NAL units are mapped onto PES packets which are encapsulated in TS packets
>which are encapsulated in RTP packets over UDP over IP (wow!!)?

No, the RTP payoad format for H.264 is defined by RFC 3984.  NAL 
units are packed directly into RTP packets (Transport Stream framing 
is not involved).

>In fact I want to find the NAL header inside the RTP packets!

(I'm assumig here that you're using VLC to *receive* H.264/RTP 
streams.  As far as I know, VLC currently doesn't support *sending* 
H.264/RTP streams.)

The data delivered by the RTP client module 
"modules/demux/livedotcom.cpp" - to the decoder - automatically 
begins with a NAL header.

Note that must be using a recent snapshot of the VLC code, and use 
version 2005.07.23 (or later) of the "LIVE.COM Streaming Media" code 
<http://www.live.com/liveMedia/>

>  Does anybody
>know where the NAL header is located? In this header there is information
>about the  frame type contained in the NAL payload.

See RTP 3984

>Does anybody know any other way to acquire the frame type contained in an
>packet?

As I noted above, it will be at the start of each block of data 
delivered to the decoder.  You don't need to do anything; this is 
done automatically.



	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