[Martin Rendall]

Hi,


I was just toying with 48Hz output the last couple of nights, and managed to get a stable image. I thought I'd post my configuration, and request that others do the same. I'd like to try it a few different ways to compare and contrast.


So,


- vertical scan rate set to 47.952Hz. Output is 848x480p.

- Zoom Player 4.03 Pro

- VMR9 Windowed

- WinDVD Video and Audio Codecs with the Abstract filter workaround

- FFDShow doing a light blur and denoise, and scaling to 1440x960

- Reclock 1.4 locked to 23.976Hz

- ATI 9800 Pro with Catalyst 4.7 drivers, with AA and AF active at 4X each. Vertical sync disabled in driver

- AnyDVD

- P4 @ 3.2 with HT on.


Pans seem smooth but sometimes blurry. I'm not sure if I'm getting the best picture here.


Thanks!

Martin.

 

[pcgeek]

Probably most important would be what projector/display and how do you have it connected? I had powerstrip set up to do [email protected] Hz and reclock locked fine but I'm driving a G70 and the refresh rate was too low for me (could see flicker in bright scenes) so I switched to 71.928Hz instead. I did this with a ATI 9600 Pro at the time.

 

[Martin Rendall]

I guess what I'm really looking for are alternatives to see which produces the best deinterlaced image.


But I think everyone would benefit from a few different setup examples. Well, everyone who's running 48Hz, which is probably a very small niche of those here.


Martin.

 

[pcgeek]

So, everything above 24 Hz at the correct exact multiple is going to have the exact same deinterlaced image being fed to the projector. Any differences in the image on the screen are going to be the projector handling the frequency fed to it (some have claimed better quality when not driving CRT projectors so hard). On the software and PC side of things it is producing 24 frames per second and the video card is just displaying each frame 2 or 3 times (48 vs 72 Hz). Trimension DNM is the only case I know of where the actual deinterlacing changes and they actually produce 60 fps with interpolated images in between.

 

[Martin Rendall]

pcgeek,


OK, so here's my confusion. A quick review of the Secrets Progressive Scan page deals with a sample of four 24fps frames. It shows how these frames are stored on disc as 10 interlaced fields (or fewer if mpeg optimization eliminates the duplicates), how these 10 interlaced fields are rebuilt into 4 frames, and how they are output at 60hz progressive to achieve the best representation possible, given the source encoding and output frequency.


All well and good. So for 48hz, one can imagine that the assembled 4 progressive frames are output in a 2-2 pattern (that is fr1, fr1, fr2, fr2, fr3, fr3, fr4, fr4 for 48Hz - as opposed to fr1, fr1, fr1, fr2, fr2, fr3, fr3, fr3, fr4, fr4

for 60hz).


Now, the signal to the display device is progressive, so the deinterlacing (or re-interleaving as Secrets calls it) is being done in software. If I understand correctly, this is actually being done by the video codec.


OK, so if this is all true, then the codec is the point where errors can occur. It may be displaying output frames in a 3-1-3-1 fashion, for example, or something else again. It may be incorrectly building frames if it got confused. It may be getting confused by poorly encoded dvds and outputing something else wrong. It needs to be the smart bit. If things are configured right, the display should just be showing what it receives without any encoding.


Reasonable so far?


Now, the question was what setups work for other people. I think it's reasonable since I couldn't get either the dscaler 4 app, nor the dscaler 5.003 mpeg decoders, to properly deinterlace film material at 48hz. I also noted that some ffdshow settings, which worked great at 60hz, blew up at 48hz.


Martin.

 

[pcgeek]

Sorry, I was already under the impression you were comparing to other multiples of 24, not something like 60Hz If you have an output device that can run a native refresh rate that is an exact multiple (or really close) of the film rate (23.xxx) then you will get a much better experience than 60Hz. 60 works OK for interlaced output devices because the images are actually "blended" at the edge cases to create for a smooth transition but nothing beats a progressive display that displays the frames exactly like they were when it was on film (trimension aside). The catch comes in when you have a digital display device that has it's own native refresh rate in which case you usually want to drive at that rate but having a CRT I haven't had to deal with this (this is why I asked about your actual setup).

 

[Martin Rendall]

pcgeek,


Ah. Well, my display is the Infocus 4805, which does do 48/1.001 Hz (but not 72/1.001 Hz). You can hear the colour wheel slow down when you set the resolution. But I still wonder if I have the software setup right.


Martin.

 

[pcgeek]

If you're getting a good pixel perfect lock out at 48Hz then that part of your software setup is fine and any issues you're going to have are not going to be because of 48Hz (specially fluid movement but blurry). You may want to put up a topic asking for the best ffdshow settings for low-res display (specify DLP, pixel perfect and the resolution as well). My guess is that your only area that may need tweaking to improve at this point would be the actual post-processing on the image. Unfortunatly I'm running a very different setup and what I'm doing probably won't translate well.


On a side nte, I haven't heard anywhere that AA and AF on ATI cards actually does anything for the VMR output (all I have seen is on Nvidia where it sharpens the image and supersamples). Not sure if it could be causing any grief there.

 

[Martin Rendall]

pcgeek,


Thanks for the comments. So you believe that the WinDVD codec is doing the right thing at 48Hz?


I think my next step will be to disable the AA and AF settings and ffdShow, and just run the straight codec. See what I get.


I've noticed reclock settings have a huge impact on smoothness, but I get judder and stutter without it, so I need it. Locking it at 24/1.001Hz seems to be best, but at the end of the day, I'm just poking around in the dark. But at least it's fun!


Martin.

 

[pcgeek]

Any of the codecs will do correct 3:2 pulldown (convert to 24 Hz) so yes, that part should be fine. Reclock is needed to get the codec to feed the data in using the video signal as the clock so that will usually have the huge impact on smoothness you saw.