That checkerboard pattern for alpha channel was a real slugfest.  It was done in software mode for a while, but never worked in OpenGL.  Over time, lions used Cinelerra a lot just for creating text on a transparent background, since the Gimp has such a horrible titler.  The checkerboard proved essential when working with alpha channels & OpenGL was proving essential in 4k, so it was finally time to port it to OpenGL.

OpenGL mode uses a bunch of hacks to improve speed.  It doesn't really use YUV or floating point all the way through.  It doesn't really use hardware all the way through & it doesn't really use an alpha channel unless the timeline has transparency leaking through.  It was written in 2005.  Software mode leapfrogged it for a while, by getting some diabolical hacks of its own.  But with the rise of 4k, OpenGL once again became the dominant mode & it was annoying not to have the checkerboard.

The checkerboard is actually implemented twice.  One version is used for showing single frames & is performed in the final software alpha multiply step.  The other version is used for showing video & is performed during the 1st clear operation of the output frame.  Compositing during video playback is done at the screen resolution rather than the project resolution & always in RGB.

There are still some glitches.  Changing the fader or projector during playback won't show the checkerboard until playback is stopped, if playback was started in a state where there was no transparency.  It only enables the alpha channel if it's required when playback starts.

Having 2 different video playback drivers which require rewriting all the playback routines is not ideal.  The playback routines are effectively rewritten 12 times to support 6 color spaces & 2 drivers, though preprocessing optimizes some of the rewrites.  All sane programs now do everything in hardware & they just use floating point RGBA.  If it's too slow, just buy a more expensive graphics card.  There's no Davinci Resolve for raspberry pi or cheap laptops.  A smarter way might be to abandon the YUV & the non alpha modes.

For now, lions have had uses for all 6 color models, if only to get higher speed.

In other software news, the lion kingdom finally finished its 60 day quest to play up to 100 million credits in Asphalt 9.  None of the credits were bought or exchanged from tokens.  After hitting around 90% of the campaign, the only way to move up in this game is to accumulate credits.  They release a new car every month, so there's no value in playing for new cars.  They add more career events every month which require new cars, so there's no attainable end of the campaign.  

Finally got around to studying 1 problem lions have had.  Manely, why they get diarrhea from certain fruit juices that should be benign.  The problem is not being half human or cancer, but a limit to the amount of fructose lions can digest.  A lion body can only digest around 7oz of orange juice, so drinking 52oz of orange juice after running is well known to cause diarrhea.  15oz of fruit juice has been managable.  32oz of fruit juice has caused diarrhea.  Coconut water also apparently causes diarrhea in large quantities because of sodium phosphate.

Lions have no natural inhibition on the amount of fruit juice they can drink.  Running just amplifies a lion's craving for fruit juice to infinity.  They seemed to handle soda better, probably because they couldn't drink it as fast without getting gas.  It seems the lion kingdom needs to go back to bottled water.

Much like anti vaxxers, the internet is caught up in giving itself diarrhea for health benefits. Look, don't give yourself diarrhea unless you're constipated.