is a source running at 24 fps?

The PureCinema film mode can reverse telecine 24 fps (frame per second) film material and display it at a native 72 Hz. A Blu-ray player can transmit a movie over HDMI at its original 24 fps and have a Kuro display this at 72 Hz. This is great and it eliminates the effect of 3:2 pull-down induced film judder. So how can it be determined if a Kuro is being fed a source at a 24 fps rate?

The Sony BDP-S350 Blu-ray player has a "24P" blue LED that lights up when 24 fps material is being output. This is a great feature since it is rather tricky to correctly configure the S350 for 24P output. Unfortunately there is not an easy way to query a Kuro's refresh rate. Other than observing the smoothness of motion and pans, there is no way to tell if PureCinema is actively performing reverse telecine. Switching an HDMI source to be a PC input is a trick that will report the input frame rate.

Here are the steps to check the refresh rate of an HDMI source:

1. Select HDMI input
2. Press Home Menu
3. Enter Setup
4. Enter Option
5. Enter HDMI Input
6. Select PC from the Signal Type submenu
7. Exit menu
8. Press Display to see the refresh rate
9. go back to step #1 and change Signal Type back to Video
   

Unless your source is a PC you probably won't want to keep your HDMI in PC mode since it has a number of picture ramifications that are not good for general TV and film viewing. It would be a really nice feature if Pioneer gave the Kuro a special control panel screen that displayed internal information like frame rate, 720p or 1080i resolution, MPEG2 bit rate, AC3 channels and bit rate, and full PSIP information.

PureCinema film mode

The Pioneer Kuro has a special film mode feature called PureCinema that engages a couple different 24 fps (frames per second) processing algorithms. One of the algorithms helps with film mode de-interlacing, while the other two algorithms produce smoother motion by performing a reverse 3:2 pull-down (inverse telecine) operation and then interpolating the in-between frames or up converting to a 72 Hz frame rate.

The Pioneer Kuro has a native progressive video refresh rate of 60 Hz. Interlaced input sources (480i, 1080i) need to have their even/odd fields reassembled (de-interlaced) first to be progressively displayed. This is called de-interlacing and it removes the teeth artifacts during fast motion and pans.

PureCinema parameters:

• Off - deactivates PureCinema
• Standard - only works with 480i and 1080i sources, de-interlaces
  
• Smooth - produces smoother moving images by frame interpolation
  
• Advance - activates 72 Hz refresh rate for 3:3 pull-down of 24 fps source material for smoother moving images

None of these modes work when the input signal is 1080p60. Speculation as to why is that there's insufficient video processing resources to handle the higher bandwidth of a 1080p60 stream. Standard setting only works with interlaced sources (480i and 1080i). Smooth and Advance settings work with 480i, 480p, 720p, and 1080i input sources.

Standard and Smooth settings display at the standard 60 Hz frame rate. The Advanced setting displays film material at a 72 Hz frame rate. Note that a 72 Hz refresh rate for 3:3 pull-down is automatically engaged whenever a 1080p24 signal is input regardless of mode setting. It doesn't hurt though to play it safe and select Advance mode anyways. Note that 24 * 3 = 72.

Like film in cinema, many prime time TV shows are also recorded at a 24 fps rate, and funnily enough sometimes with a video camcorder. So the Advance mode can be useful for more than just DVD and Blu-ray playback.

Judder
What is "dejudder" and how is it related to all of this? Judder is the 3:2 hitching that occurs when 24 fps film material is displayed at a TV's native 60 Hz frame frame. Judder creates a periodic chugging effect that is easiest to see with slow pans or during scrolling credits. Dejudder is the process of removing judder by using video processing. Removing judder, like how the Kuro does with its 72 Hz frame rate is a good thing as it preserves the natural flow of 24 fps film.

Many new LCD flat panels have a 120 Hz refresh rate feature that uses frame interpolation to create smoother motion. Interpolating frames improves the LCD panel's poor motion resolution so LCD manufacturers like this feature because it boosts their specifications. Plasma displays have a superior motion resolution and don't need this technology. Note that with 24 fps film material the LCD's 120 Hz 5:5 pull-down has a similar effect to the Kuro's 72 Hz 3:3 pulldown. Also, the Smooth mode with the Kuro's PureCinema feature does frame interpolation but displays it at 60 Hz.

So dejudder used to mean removing the 3:2 hitching of 24 fps film material by playing it back at a native frame rate multiple of 24. Unfortunately dejudder has morphed into an ambiguous, overused, and abused term that includes both native rate playback and the frame interpolation of all sources (24, 30, and 60 Hz). Some people dislike the frame interpolation feature and disable it. Some LCD HDTV's don't allow 5:5 pull-down of 24 fps film material unless interpolation is enabled and this further complicates the issue. So when you hear the term "dejudder" make sure you understand if it means interpolation, native rate playback, or both.

I keep the PureCinema option set to the Advance mode and it works fine for Blu-ray, DVD, and broadcast HDTV sources. The algorithms are smart enough to prevent odd artifacts most of the time.