[linux-dvb] Re: vbv delay/buffer overflows on VBR statmux

[Oliver Endriss <o.endriss@gmx.de>]

Gregor Lawatscheck wrote:
> At 18:08 21/05/2003, we wrote:
> >Table 14: Video Input Buffer (theoretical + decoder delay +
> >
> >  > display synchronization = 229,376 + 52,000 + 75,000)
> >  > which is surprisingly close to 230 k as "theoretical" input.
> >  > Maybe this also explained why higher vbv_delay (i.e. no delay by
> >  > setting 0xffff) had an effect freeing some memory?
> >
> >Maybe.
> >Some numbers in the RTSL include files also are different to the
> > ones in the TI datasheet. Without more knowledge about the
> > microcode one can only speculate.
>
> Section 7.7.2 says something about the MPEG standard:
> The video input buffer, which is located in the SDRAM, is made up of
> three components: a theoretical rate control buffer whose size is
> specified in the MPEG-2 video standard (229,376 bytes); a buffer
> space to compensate for the decoder delay (52,000 bytes); and
> additional storage space to synchronize the video decoder timing with
> that of the NTSC/PAL encoder Vsync timing (75,000 bytes).
> Could that be why 230 k works fine or is this not the video memory?

According to the datasheet (table 16, p.39), a split buffer 
configuration SDRAM 160 KB / DRAM = 197 Kb should work. 
Obviously it doesn't.

> Moreover there seems to be seperate memory  for I-/P-/B-FRAME of up
> to 500 k each, I'm not quite sure what the vid memory does beyond
> holding the frames - things like timing info -- but then so much?

You looked into the NTSC table (p.20), right? I wish we could use this 
setup! This would increase OSD memory size by approx. 260 KB and we 
wouldn't have any problems. Unfortunately, we have to use a PAL setup 
(p.21) which needs 2* 607,5 KB for reference frames plus 373 KB for B 	
frame.

2 MB SDRAM are not enough for a PAL system with large OSD.
I guess it's not possible to move some or all OSD buffers into DRAM?

Oliver


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