FRC, the ultimate tearfree video solution

[legume]

You'll need 50 Hz capable monitor for European dvb

Cool sounding project - I've been looking into getting a decent lcd monitor for some time, but none of the specs I've seen go down to 50Hz.

Have you found that it is possible to underclock LCDs?

[bridgman]

That's what I thought, but I was a bit confused by the claim of this being "the ultimate tearfree video solution" when it only seems to solve the frame doubling/skipping artifacts. Do those also show up as "tearing" somehow?

Think of "ultimate tear-free" as meaning "tear-free without the side-effects", not "even more tear-free"

[vesa]

That's what I thought, but I was a bit confused by the claim of this being "the ultimate tearfree video solution" when it only seems to solve the frame doubling/skipping artifacts. Do those also show up as "tearing" somehow?

You know phase and frequency are quite convolved Mathematicians will entertain you ad nauseam... Simply put phase error will result from frequency error. The relative phase also 'slips' depending on the freq error.

When you get rid of the freq and phase error there is nothing to tear apart. Everything is smooth as butter. That includes no visual tricks whatsoever and is also provable to be 'perfect'.

[Ex-Cyber]

That's what I thought, but I was a bit confused by the claim of this being "the ultimate tearfree video solution" when it only seems to solve the frame doubling/skipping artifacts. Do those also show up as "tearing" somehow?

[bridgman]

Yes it is. You fix tearing by synchronizing frame buffer updates with the display refresh rate, however that introduces a *new* set of artifacts since the display refresh rate is not quite the same as the frame rate in the video stream. Tear-free code ends up occasionally skipping or doubling frames, depending on whether the video stream frame rate is higher or lower than the display refresh rate, which results in some jitter.

As with tearing, some people can see this jitter while others can not, which results in some interesting threads on the A/V forums.

The way you deal with the skipping/doubling jitter that comes with regular tear-free code is by synchronizing the display refresh rate to the video stream rather than skipping/doubling frames to synchronize the video stream to the display.

Make sense ?

[Ex-Cyber]

I thought tearing was typically caused by mid-frame display updates; i.e. a phase problem rather than a frequency problem. Is that not the case?

[vesa]

Is there much use of frame rates over 30 ? My understanding was that 24, 25 and 30 pretty much covered all of the currently available DVD and BD disks (assuming 50i and 60i are displayed as 25p and 30p respectively). I know other formats are supported but AFAIK they aren't actually used much...

That's the gist of the problem. 50i and 60i _must_ be displayed as 50p and 60p on progressive displays to preserve the temporal resolution (fluid movement). I'm still subject to precensoring with links, so my 'official reply' is in the buffer... I'm delighted to see you here though. Any chances to push those patches forward? The author has had very much difficulties to get any discussion going on the relevant lists.

[bridgman]

Is there much use of frame rates over 30 ? My understanding was that 24, 25 and 30 pretty much covered all of the currently available DVD and BD disks (assuming 50i and 60i are displayed as 25p and 30p respectively). I know other formats are supported but AFAIK they aren't actually used much...

[vesa]

This gets real interesting when you combine it with a 120Hz display, which can run at an exact multiple of either 24 or 30 Hz frame rates.

Not to mention that one needs 300 Hz to be really universal. For 24, 25, 50, 60, 100 Hz

[vesa]

I agree with you on this. Fortunately it is not necessay every time. In case of the progressive 24 fps material 50 or 60 Hz will work quite well. Only real video hifists would like 48 or 72 Hz ... Also FRC does the adjustment without full crtc reset (unlike real mode change), so there is no blank period to be seen.

Naturally it all boils down what's the purpose of the machine. I'm running my desktop at 50 Hz all the time because most of the material I work with is digitized PAL or 50 Hz DVB. Also I save a bit of memory bandwidth by using lower refresh. That's on itegrated display controller Q965 and the mb has very nice property of being fully synchroronous with all system clocks (video, audio, I/O...) phaselocked to main crystal reference. (Intel application notes are interesting, btw.) The only grief is bad power bypassing to ALC260 audio chip ? maybe I'll fix it someday...

Even though FRC seems to be very SCART centric, it is really just one use of it.

Xtiming script gives better flexibility than cvt as it allows one to tweak sync times too. That way it is possible to get even frequencies without rounding errors. DVI connected LCD seem very tolerant to adjustments.

http://xtiming.sourceforge.net/cgi-bin/xtiming.pl

Some forgotten links follow:

http://www.kingcot.eclipse.co.uk/unichrome/tvoutTest.html

The real test for deinterlacing. Remember that vsync works often only in full screen or in big window. Don't kow the reason though. Kaffeine with ScalerBob is the closest imitation of crt tv and
mplayer -vf yadif=1:1 -fs will get somewhat processed, but very good result.

http://www.linuxtv.org/wiki/index.php/Development:_The_DVB_Decoder_Challenge#Screen.2FDecoder_Sync_Aliasing