[vlc-devel] Small utility to add RTP headers to raw UDP MPEG-TS

[Rémi Denis-Courmont]

On Mon, 11 Aug 2008 14:18:02 +0200, Christophe Massiot <massiot at via.ecp.fr>
wrote:
> On Mon, Aug 11, 2008, Marian Ďurkovič wrote:
>> > It is probably of no importance to you, but please notice that the RTP
>> > timestamp is not correct : the spec says it should be in the same
> scale
>> > and origin as the PCR, which is not the case here (since it is
> generated
>> > from the wall clock and not from the stream).
>> 
>> Yes, I'm aware of this - but in our environment the RTP headers
>> are used to identify stream type and ensure correct packet order.
>> All timing is taken from the transport stream by hw or sw
>> demuxer i.e. the RTP timestamps are in fact trashed.  
> 
> Same for everyone - I doubt somebody actually uses the RTP timestamp in
> a TS application.

Yeah. Even the MPEG-TS payload format spec says 
> 
>> Anyway, I'll be glad to fix it if there's an easy way to extract
>> PCRs from the TS - any hints or examples for this?
> 
> Not quite simple :
>  - filter PID 0 and build the PAT
>  - filter the PID of the PMT of your program (what to do if there are
>    several programs ??) and build the PMT
>  - get the PCR_PID from the PMT
>  - get the PCR from the adaptation field layer of the PCR_PID
> 
> Alternatively, you can also search all PIDs for an adaptation field
> containing PCR, and then consider it is the PCR_PID, but funny boys can
> also send PCRs on PIDs which are not supposed to carry them. Should work
> with most streams though.
> 
>
-- 
Rémi Denis-Courmont