Re: [PATCH] drm/edid: Add both 60Hz and 59.94Hz CEA modes to connector's mode list

[Andy Furniss <adf.lists@gmail.com>]

Daniel Vetter wrote:
> On Fri, May 31, 2013 at 03:23:41PM +0300, ville.syrjala@linux.intel.com wrote:
>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>
>> Having both modes can be beneficial for video playback cases. If you can
>> match the video framerate exactly, and the audio and video clocks come
>> from the same source, you should be able to avoid dropped/repeated
>> frames without expensive operations such as resampling the audio to
>> match video output rate.
>>
>> Rather than add both variants based on the CEA extension short video
>> descriptors in do_cea_modes(), add only one variant there. Once all
>> the EDID has been fully probed, do a loop over the entire probed mode
>> list, during which we add the other variants for all modes that match
>> CEA modes. This allows us to match modes that didn't come via the CEA
>> short video descriptors. For example one Samsung TV here doesn't have
>> the 640x480-60 mode as a SVD, but instead it's specified via a detailed
>> timing descriptor.
>>
>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> ---
>> A few people requested this. Originally I was a bit opposed to it, but
>> when I thought about it a bit more I figured if the audio and video
>> clocks come from the same source (or happen to be close enough w/o
>> significant drift), this could provide a better A/V sync w/o resampling
>> tricks.
>
> Yeah, I think this should be useful for a bunch of people. I've recently
> chatted with a few xbmc folks on #irc and one thing they've requested is
> mode fine-tuning. For DP we should have plenty of precision, but for HDMI
> we'd need to (slightly) frob the vtotal ever so often to compensate. With
> some runtime-tuning a la npt we should have perfect a/v sync without any
> audio resampling.

Apologies, for jumping in here, but assuming I haven't missed anything 
you've done already: do you have any plans for supporting CEA interlaced 
modes?

That's assuming they actually need any more support - I only know that 
they are slightly wrong for me testing with radeon + my TV - are they 
tested and known to work / not work on intel hw?

The symptom I get is not instantly obvious - the second half of the 
bottom line gets rendered and repeated as the top line.

For me the reason that proper support could in theory be useful, is that 
were there in future a way to sync up properly,  my TV will do a nice 
"free" deinterlace. Even on a fast quad core PC doing one as good on cpu 
is not possible for HD 50i.