htpc and 23.976fps
#1
hi everyone.. i wanted some feedback on using my htpc with true 23.976 fps

i have the setup below and running movies at 23hz (23.976 fps) i get a quick hicup/sutter every couple of minutes.. had people over they didnt notice but im the nerd and since i knw what to look for.. so wondering if anyone has feedback or can tell me if something is wrong in my setup

win7 x64 (home premium)
amd x3 450 (triple core)
nvidia gt430
4gb RAM
Onkyo sr-5508 preamp
Epson 8700ub projector
MPC-HC with ffdshow codecs (video out is YV12 and audio is bitstream)
dual monitor setup (main is vga output-LCD at 60hz other is HDMI to preamp/projector 23hz)


i have the hdmi from video card going to an onkyo preamp - from the preamp hdmi output to the projector

i have mpc-hc/ffdshow sending bitstream audio to the preamp
MPC-HC is running in overlay mixer mode

i get the projector to read 23.97hz under signal info and MPC to read 23.97 as well.. but again the hicup happens every minute or 2 (which last a second or less)

i tried enabling/disabling 4:4 pulldown and same thing..

I also enabled/disabled lip sync on my preamp and same thing (since i have a long run b/w htpc/preamp/projector the calucated distance is 120ms)

when i run the projector in 59 or 60hz ..i get no hicup but my goal is to run it at native frame rate

i checked my CPU/RAM usage during playback it varies b/w 12-18% on CPU and 20-22% on RAM ..so i dont think its a matter of slow CPU or not enoug RAM

so looking for any feedback? thanks!!
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#2
Hello. This: "(which last a SECOND or less)" is the major issue. If it was a simple mismatch of framerate (e.g. 23.97 vs 23.976) each stutter would be a ***single frame***. Therefore the stutter would only last about ~1/24th of a second, every few seconds (how many seconds between stutters would depend on how far your Nvidia was from the reference 23.976 framerate).

Are you sure the stutter lasts that long? Can it really last a whole second? Or anything close to a second? If so, it isn't an issue with 23.976 or an issue with your video card or projector at all.

If it is a single frame stutter every few seconds then it is almost certainly because your Nvidia is not outputting exactly 23.976. Almost no video cards do output 23.976 exactly. Even if it is very close (like 23.975), you will get a single frame stutter every 41.7seconds, by my calculations.

Achieving perfect 23.976 playback with a PC is extremely difficult (some would say "impossible" right now), due to the numerous PC clocks. It is easy in a Bluray player - a single clock to program to and no clock synchronisation issues.

Good luck.
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#3
what happens when u use xbmc to play your movies?
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#4
eightysix.agent Wrote:Hello. This: "(which last a SECOND or less)" is the major issue. If it was a simple mismatch of framerate (e.g. 23.97 vs 23.976) each stutter would be a ***single frame***. Therefore the stutter would only last about ~1/24th of a second, every few seconds (how many seconds between stutters would depend on how far your Nvidia was from the reference 23.976 framerate).

Are you sure the stutter lasts that long? Can it really last a whole second? Or anything close to a second? If so, it isn't an issue with 23.976 or an issue with your video card or projector at all.

If it is a single frame stutter every few seconds then it is almost certainly because your Nvidia is not outputting exactly 23.976. Almost no video cards do output 23.976 exactly. Even if it is very close (like 23.975), you will get a single frame stutter every 41.7seconds, by my calculations.

Achieving perfect 23.976 playback with a PC is extremely difficult (some would say "impossible" right now), due to the numerous PC clocks. It is easy in a Bluray player - a single clock to program to and no clock synchronisation issues.

Good luck.

Well, this is where the "Sync playback to display" setting comes in, it synchronizes the videoframes to the vertical blank of the display, and then it resamples the audio to keep it in sync with the video (as long as you use the resample sync method and don't use passthrough).

This way, the video will always be perfectly synchronized to the display, even if the refreshrate is a little off (assuming it works right, sometimes it doesn't).
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#5
What happens when you shutdown XBMC and then try playing the file from MPC. Any better?
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htpc and 23.976fps0