[vdr] Re: Still pictures with latest CVS driver

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Andreas Schultz wrote:
> 
> Hi,
> 
> Klaus Schmidinger wrote:
> 
> > Stefan Huelswitt wrote:
> >
> >>On 24 Nov 2001 Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de> wrote:
> >>
> >>
> >>>Unfortunately I still have no idea why VDR can't display still
> >>>pictures with recent CVS diver versions, although Ralph insists
> >>>that the I-frames they use _can_ be displayed (and he proved that
> >>>to me by sending me such a frame, so I have to accept that from
> >>>his point of view the driver's 'play_iframe()' function _is_
> >>>working).
> >>>
> >>And what is the difference between your iframes and Ralph's?
> >>
> >
> > I wish I knew ;-)
> >
> > I have uploaded the files
> >
> >   ftp://ftp.cadsoft.de/pub/etc/cim.mpg
> >   ftp://ftp.cadsoft.de/pub/etc/kls.mpg
> >   ftp://ftp.cadsoft.de/pub/etc/play_still.c
> >
> > The first one contains Ralph's I-frame (@Ralph: I hope it's ok with you
> > that I have uploaded this file?!), the second one is one of VDR's I-frames,
> > and the third one is a small example program that takes the name of a file
> > and displays the I-frame in that file as a still picture (I also got this one
> > from Ralph). Interestingly, with the unpatched driver cim.mpg works, but kls.mpg
> > doesn't. If you apply my patch to dvb.c, kls.mpg works (and IIRC cim.mpg doesn't
> > work any more, but I'm not sure about that).
> >
> > If anybody can find out what prevents kls.mpg from being displayed, I'd appreciate
> > any hints. BTW: kls.mpg may contain sequences with many subsequent 0x00 bytes.
> > These are former AC3 audio packets that have been erase by overwriting them with 0x00.
> > AFAIK there may be any number of 0x00 bytes in an MPEG stream, so this shouldn't
> > make a difference.
> 
> Sorry no solution, but some observations.
> 
> play_iframe() tries to fill a 400kb buffer by repeating the I-frame n+1
> times (n = 400000/size of the frame). It does so by extracting only
> parts of the frame, that contain video data. Your change effects IMHO
> only some tail fragments of the I-frame, but could lead to the buffer
> filling faster.
> 
> It could be, that due to you 0x00 fills and some apparent stuffing bytes
> in your frame, you never reach the magic fill level. This might be fixed
> by using "n=MIN_IFRAME/len+2;" in dvb.c.
> 
>     Andreas

As reasonable as this would seem, it didn't help :-(
I tried "n=MIN_IFRAME/len+2;" and also doubled the MIN_IFRAME value.
But the behaviour was always the same.

I guess if there was a way to immediately make the MPEG decoder show the
current frame (as requested in your message "[linux-dvb] DVB buffer flushing ?")
Ralph would have used it in play_iframe()...

Klaus
-- 
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Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
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