[vlc-devel] Re: Re : VLC behavior

[adrian hornsby]

Hi again,

When one GOP is droped from the MPEG2 ts stream, VLC
goes to the next I frame (I3) but does it drop the
frame B1 and B2 that actually refers to a P frame
before the GOP ??

> 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.
> > 
> > -- 
> > ##################################
> > http://thisisallaround.freezee.org
> > ##################################
> > 
> > 		
> >
>
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> > -- 
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> > 
> > 
> 
> 
> ****************************
> Hornsby Adrian
> 
> This is all around .....
> http://hornsby.freezee.org
> 
> ****************************
> 
> 
> 	
> 	
> 		
>
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=== message truncated ===


****************************
Hornsby Adrian

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

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


		
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