Quoting Nicolas Huillard:

> Mark Adams a écrit :

> >> ------------------------
> >> Try adding a printk in viafb_wait_for_sync (via_fbobj.c), just before it
> >> returns:
> >>
> >> printk(KERN_INFO "wait vsync: %d %d %d\n", field_option, p->irq_cnt & 1,
> >> ret);
> >
> > OK, so we see this:
> >
> >> Feb 11 11:39:47 vdr kernel: wait vsync: 3 0 25
> >> Feb 11 11:39:47 vdr last message repeated 2 times
> >> Feb 11 11:39:47 vdr kernel: wait vsync: 3 1 25
> >> Feb 11 11:39:47 vdr last message repeated 2 times
> >> Feb 11 11:39:47 vdr kernel: wait vsync: 3 0 25
> >> Feb 11 11:39:47 vdr last message repeated 2 times
> >> Feb 11 11:39:47 vdr kernel: wait vsync: 3 1 25
> >> Feb 11 11:39:47 vdr kernel: wait vsync: 3 1 25
> >
> > field_option 3 is a wait for a kernel-assisted flip to complete.  The 25's
> > (HZ/10) mean that the wait calls are returning immediately (presumably
> > because a fair amount of processing was required to get the next frame
> > ready
> > and the previous frame had been displayed by that point).  The mixture of
> > 0's and 1's means that the video is sometimes on the top field and
> > sometimes
> > on the bottom when the wait happens.

"when the wait happens": Does that mean we are somtimes displaying top field
first, and sometimes bottom field first ?
These messages are within the same second.

Softdevice allways does layer->SetFieldParity(fieldParity); // fieldParity is 0

> >
> > All that is fine provided that you're using triple buffering.  That's
> > perhaps something I should enforce when this method is being used and fall
> > back to the old method if not.
> >
> > Are you using triple buffering?
>
> Softdevice developpers should give a sound answer.
> The logs say :
>
> [surface capabilities] videoSurface: videoonly flipping triple-buffered
> PixelFormat = 0x08100609
>

You should get other messages printed to stderr too, like:
[dfb] Set DLBM_TRIPLE for layer [%s]

or if enabling triple buffering fails:
[dfb]: SetParms (): failed to set buffermode to triple, will try back video

But this requires softdevice option "viatv" to be set.

Stefan Lucke

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