HQV (Test 9)

Test 9: Film Cadence

From the HQV manual:

As mentioned in the previous section, program content for television is often created using different picture refresh rates and cadences. Here are some of the more common frame rates and cadences:

• Documentaries shot on high speed film use 30 frames per second frame rates resulting in a 2:2 cadence

• Professional DV camcorders and the new HDV models can capture video at a 24 fps rate for a film ‘look’, but employ a special cadence (either 2:2:2:4 or 2:3:3:2) for more efficient digital compression

• To allow more time for commercials, theatrical films shown on television are often sped-up or edited to remove 1 out of every 13 video fields after 3:2 pull-down has been applied, resulting in a cadence of 3:2:3:2:2.

• Animation is often rendered at 12fps. Two pull-down cadences can be used to convert this to the 30 fps broadcast standard. Doubling every frame, and then applying 3:2 pull-down to the resultant fields will generate a 5:5 cadence. Applying 3:2 pull-down to the frames (rather than the fields) will generate a 6:4 cadence.

• The Japanese ‘Anime’ format is often rendered at 8 fps. To convert this to 30 fps, each frame of animation is repeated three times, and then 3:2 conversion is performed for an effective cadence of 8:7.

Different film cadences may appear to strobe on TV sets, which is considered normal. You may see this strobing effect in movie theaters as well, but it usually isn’t as apparent as on an interlaced display. If the video processor can’t detect and lock onto all of these different sequences, the result will be half resolution images.

The ability of a processor to detect and correct for a given film-to-video cadence affects image detail and may introduce scan line artifacts (‘jaggies’) as the video processor defaults to video mode. Observe the lines in the coffee cups and watch to see if they appear to jump or flicker, a sign of incorrect cadence detection resulting in half-resolution images. The text in the newspaper may also exhibit moiré and interlaced scan line artifacts.

ATI Radeon X1900 All-in-Wonder Video Card Review - Graphics Cards  1

ATI Radeon X1900 All-in-Wonder Video Card Review - Graphics Cards  2

Sample ATI Screenshot; Total Score: 40

ATI Radeon X1900 All-in-Wonder Video Card Review - Graphics Cards  3

Sample NVIDIA Screenshot; Total Score: 30

There are eight individual cadence tests that are run here, with each worth 5 points.  I only showed a sample from each of ATI’s and NVIDIA’s results in the screenshots. 

ATI’s Avivo correctly recognized all 8 patterns and the video playback was excellent.  However, the NVIDA PureVideo didn’t seem to get the 2:2 or 2:3:3:2 cadences correctly and jaggies were seen through out those tests.

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