[vlc-devel] Re: Re : VLC behavior

[adrian hornsby]

Well, actually I checked the sending order and here is
what I get :

A typical GOP in display order is :
B1 B2 I3 B4 B5 P6 B7 B8 P9 B10 B11 P12

the corresponding bitstream order is :

I3 B1 B2 P6 B4 B5 P9 B7 B8 P12 B10 B11

So, there is something I dont really get here.

Another thing, If I put TS packet with PID 8191 (NULL
PACKET) will VLC ignore them no mater the payload ??

thanks





--- hornsby <adrian_hornsby at yahoo.co.uk> wrote:

> On Tuesday 08 November 2005 22:57, Jean-Paul Saman
> wrote:
> > adrian hornsby wrote:
> > >>>hornsby wrote:
> > >>>Hi everyone,
> > >>>What would be VLC behavior if in a MPEG2 TS
> stream,
> > >
> > > one full GOP is
> > >
> > >>>missing
> > >>>?? would it be able to resyncro without any
> > >
> > > artifacts on the screen ??
> > >
> > >>If the first frame is an I-frame, then there
> won't
> > >
> > > be any
> > > artefacts.
> > >
> > >>Kind greetings,
> > >>Jean-Paul Saman.
> > >
> > > Hi Jean-Paul,
> > > Thanks for your answer. The problem is that a
> GOP ,in
> > > display order, never start with I frame but
> usually
> > > with a B frame. So VLC receive first an I frame
> then
> > > the B frame,  but reorder it, right ? Can vlc
> lose a
> > > bit of info ??
> >
> > I think you are wrong. An I-frame is a
> selfcontained frame, a B-frame
> > depends on other frames in 2 directions, a P-frame
> depends on an other
> > frame only in one direction. The typical sequence
> a GOP or series of
> > frames is sent is:
> >
> > IPBBBPBBBBPBBP I
> >
> > The B-frames are always sent before they are
> actually needed, but after
> > the first I-frame of a GOP.
> >
> So, if I their is an I frame, no risk to have
> anything before it,being related 
> to it ?? 
> I agree with you on the sending order, it makes
> sense. I have to check my 
> streams because I think I didn't have that sending
> order. I also was checking 
> the time_reference field and it suggested something
> else to !!
> Is their some risk that the sending order can be
> different than the decoding 
> order ??? (not the display order that is always
> different than decoding order 
> for the reason you explain)
> 
> Or should the sending order respect the decoding
> order ??
> 
> thanks again
> 
> 
> > > The thing is that I did the test, and some very
> little
> > > artifact appears on the screen, few scares.
> > > My attention is to test my splicing tool with
> VLC. I
> > > use beginning and end of GOP as splicing points.
> But
> > > of course I had to try with the exact same
> stream
> > > first. So i only remove one GOP from the stream
> and
> > > see VLC's behavior.
> > >
> > > You can use my tool to see yourself. Of course,
> VLC is
> > > so good that I tend to think the problem is in
> my tool
> > > but I checked everything and I couldn't find any
> > > explanation.
> > >
> > > My tool is build on live555.com library. You can
> > > download my tool from here.
> > > Just compile it and play the "testRelay" file in
> > > /testProgs/ directory.
> > >
> > > testRelay work on command line as follow :
> > > ./testRelay <input_multicast_address1> <port1>
> > > <input_multicast_address2> <port2>
> > > <output_multicast_address1> <port1>
> > >
> > > (i.e:./testRelay 239.252.40.1 4444 239.252.40.1
> 4444
> > > 239.252.50.1 1234)
> > > to ask splicing, press the key "s", to stop "q"
> > >
> > > The splicing tool is in the liveMedia directory
> :
> > > -MPEG2TransportStreamSplicer.cpp
> > >
> > > Thanks so much for helping me.
> > > Best Regards,
> > >
> > > I want to release a Real Time splicing tool on
> GPL, if
> > > you want to help me with little thing, please
> email
> > > me. I would really like having experts helping
> me.
> > >
> > > adrian
> >
> > Grtz,
> > Jean-Paul Saman.
> 
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****************************
Hornsby Adrian

This is all around .....
http://hornsby.freezee.org

****************************


	
	
		
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