[linux-dvb] Re: [PATCH] fix for stream corruption on budget / Nova-T cards

["Dr. Werner Fink" <werner@suse.de>]

On Mon, Sep 01, 2003 at 08:12:47PM +0200, Emard wrote:
> On Sun, Aug 31, 2003 at 06:40:04PM +0100, Jon Burgess wrote:
> > Emard wrote:
> > 
> > >This DMA corruption has been there long time around.
> > >We tried to fix it with many tweaks, that's the reason of
> > >vpeirq introduction but from your experience it seems some 
> > >data loss hole still remained open.
> > 
> > What was done before vpeirq? How far back in the code do I need to look 
> > to find this?
> 
> Before March or so, the code is dirty and pure junk which
> easily can miss DMA at PCI latency. It can work well on some
> machines but PCI latency should be well tuned.
> 
> The source or the problem was blamed on separate vsync detection 
> chip found mostly on budget cards. This chip and 7146 can have 
> slightly different timing of vsync and therefrom came the DMA blocks
> missing in the previous code. 
> 
> It could be that metzlerbro's are still using this type of 
> code in their DVB drivers
> 
> vpeirq() doesn't need to trigger on the vsync chip signal and is 
> much better solution invented by a czech developer who had 3 budget 
> cards downloading simultaneousy and had missed DMA interrupts 
> which vpeirq() completely solved.
> 
> I was using it on 2 budget cards simultaneous cards and worked fine
> for me too.
> 
> Emard

Btw: Could it be that with this patch (DVB-fix3.patch) the TS frames
are doubled now[1]?  And wouldn't it be better to use an appropiate
locking mechanism within the firmware?


         Werner

[1] My bitstreamout plugin for VDR doen't use an TS error and count
    checker for doubled frames ... and with this patch I get buffer
    overflows and staccato AC3 audio (tested with dvb-20030805).


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