[vlc-devel] Re: DVB

[Lukasz Kondrad]

On 4/26/06, Benjamin Pracht <bigben+spam at videolan.org> wrote:
>
> On Wed, Apr 26, 2006, Lukasz Kondrad wrote :
> > Hello,everyone!
> >
> > I am writing a extension to VLC media player which will allow recive
> DVB-H
> > signal. I had read the source of VLC so many days. I want to modify
> > transport stream (ts.c) demultipexer. I have alread written a part which
> > separates mpe sections, now I have a problem to which module send the IP
> > datagrams.
> > Because the IP address is map to the MAC address that 2 last bytes, I
> was
> > thinking to skip the IP header and send udp datagrams to the access udp.
> Is
> > it possible, or my thinking is worng.
> > Help me please.
> >
> > Regards,
> >  Lukasz
>
>
>
> Well, I don't know how DVB-H implementations are generally done, and I
> don't know what your project is exactly, but why trying to reimplement
> an IP stack in VLC ? Doesn't your DVB-H demodulator come with network
> device drivers ? Linuxtv drivers at least have one. That would allow you
> to use VLC to decode DVB-H streams with no (or little) modification
> (DVB-H uses RTP payload over the IP datagrams, doesn't it ?).
>
>
> In your case, the udp access module will be of little help, I think.
> Once having recontructed the RTP stream from the IP/UDP packets, you
> should send it directly to a RTP demux. Here will come an additional
> issue. VLC can only demux RTP using its ts demux (so only with TS inside
> the RTP payload), or using the live555 library. AFAIK, live555 can only
> be initialized by providing it a path to a sdp file (locally or on an
> http/rtsp server, or using SAP). It will then try to receive the
> corresponding RTP stream using the OS network layer. That means that in
> your case, you might be compelled to write your own RTP demux. This
> demux will probably need the UDP header to be able to separate the
> different elementary streams (not sure about that...). Then it would
> make sense to implement the IP stack (or just discard the
> headers, if you don't need their content) in this demux. That way, a
> possible dataflow would be:
>
> ts demux    ->  IP/RTP demux    ->    decoders
>
>       IP packets    ->   elementary streams
>
>
>
>
> Again, using the OS IP stack if possible would be much easier...
>
> --
> BigBen
>
> --
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>
>
Hi,
thanks again for your answer. It encourage me to think more and new
questions's appered.
I will say what I have done already. I am able to recognize the pid which
carry mpe and for it I wrote new functions in ts.c which creating IP
datagrams. I can take all information I need (IP addresses and ports from
UDP ) .

You wrote that vlc is only suport ts over rtp. It is not problem, as we have
our own DVB-H network at university I can change that we will send the ts
insted H.264. I will think latter how to demux when the H.264 or MPEG4 is
transmiting over RTP.
My question is where should I send the RTP stream ?? You wrote that when I
will have the RTP stream I should send it to vlc's rtp demux but I can not
find where it is.

regards and have a nice weekend:)
Lukasz
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