AV Receiver Reviews

The Tests
Before we get into the results, here’s an explanation of the tests included in this report.

Interlaced-to-Progressive (I/P) Conversion of High-Definition Sources
Since most broadcast HD content is 1080i, and most high-def displays are either 720p or 1080p, it is increasingly important that these interlaced high-definition signals are properly deinterlaced to progressive. Improper HD deinterlacing results in obvious loss of resolution combined with other artifacts. This is also a big factor with 720p displays. 1080i content must be deinterlaced to 1080p before being scaled down to 720p, or the same problems occur.

Film-based content is captured at 24 frames per second (fps) and therefore requires a different cadence to convert the 24-fps playback to the standard 60-hertz playback that most consumer devices use. This is called 3:2 pulldown since one frame is repeated twice with the following frame repeated three times to achieve 60 Hz from a 24-Hz source. 3:2 pulldown must be detected and compensated for on playback to eliminate artifacts and maintain resolution with HD sources, and this is still relatively rare among HD video-processing solutions.

Video sources, such as music and concert videos and TV shows, are captured at 30 frames per second, often interlaced. It seems easy to convert 30 fps to 60 Hz simply by doubling the frame rate, but the processor must recognize whether a source originated as video or film. So video processors often stumble with this 2:2 cadence.

HD deinterlacing tests will be referred to as “3:2 HD” and “2:2 HD” in our results tables. As we found, there was significant variation in these AVRs’ abilities here.

I/P Conversion of Standard-Definition (SD) Sources
These tests indicate how well these AVRs will handle 480i content typically found on DVD and standard-definition cable sources. Properly deinterlacing 480i material to 480p before upconversion is essential for a high-quality image from SD sources, something many AVRs on the market claim to deliver. We did tests for both film (3:2) and video (2:2) sources. SD deinterlacing tests will be referred to as “3:2 SD” and “2:2 SD” in our results tables.

Motion Adaptive Deinterlacing
This test revolves completely around SD video-based material and is often misunderstood. Video deinterlacing gets a bit tricky if some parts of the image are in motion and others are not. Motion-adaptive deinterlacing caters to both. The parts of the image that are not moving are formed by combining the fields of video of the interlaced feed, while the parts in motion are interpolated. If this is not done properly, still areas in the image are a lot softer, and objects in motion display a combing effect.

Combing is a common descriptor that refers to line breakup that becomes quite noticeable when improper deinterlacing occurs. With so much material out there originating from video, such as concert videos and TV shows, this is the most crucial aspect of deinterlacing SD video-based material.

Overscan/Cropping
If you’ve bought a digital display capable of 720p or full 1080p resolution, you don’t want a passthrough device like an AVR compromising the resolution being sent to your display by cropping pixels from any area of the image. A receiver that cropped more than five pixels from any side of the image (or top or bottom), or two sides combined, failed this test.

Video Clipping
While HDMI transmitters should be simple devices that transmit the outgoing audio/video signal as is, the reality is different. One of the biggest issues is video dynamic range. All current consumer digital video sources, including high def from Blu-ray and HD DVD, are 8-bit signals represented by 256 digital levels (0 to 256). Zero and 256 are reserved, but the other bits are used. With a standard video signal, there are two reference points within that range: Digital 16 represents reference black, and digital 235 represents reference white. All program material should be encoded to fall within this range, but this is not always the case.

Our belief is that video- processing solutions in AVRs and other video devices should leave the headroom above 235 and the toe room below digital 16 intact. Processors should not clip (i.e., render invisible) signals below reference black or above reference white. Not only does this preserve the full dynamic range of the 8-bit signal, it makes calibration of black and white levels of displays far easier. We looked at test patterns to ensure that each AVR allowed signals below reference black and above reference white to pass through. If the receiver clipped these signals, it got a failing grade.

Resolution
Here, we tested whether these AVRs preserve the full resolution of both HD and SD sources. We also wanted to be sure that analog component video sources being converted to HDMI were tested since some analog-to-digital converters tend to roll off the upper frequency response, resulting in a softer image and loss of fine detail.

For this test, we looked at the luma (black-and-white) resolution and the chroma (color) resolution for both analog and digital signals. It is important that both signals (luma and chroma) retain full resolution since it is the combination of these signals that determines the image quality you see from your display.

For resolution, we had three possible outcomes: fail, borderline, and pass. A fail is a complete loss of resolution, a borderline is a small loss of resolution in either the vertical or horizontal domain, and a pass represents no loss of resolution.

Scaling
Scaling refers to the process of taking a video source of one native resolution and converting it to another. This can involve upconverting a source to a higher resolution or vice versa. It is far easier to convert a higher-resolution source to a lower one, so our emphasis here was on scaling a standard-definition 480i source to 1080p.

We graded each AVR’s scaling using a static resolution chart. Poor represents an output with a large amount of ringing or moiré in the image. Good represents only a marginal amount of ringing and little to no moiré. Excellent means no ringing or moiré artifacts were present, and a crisp, artifact-free image was presented.

Performance Tables
Now that we’ve gone over the tests, let’s look at the results. Each table has two rows of test results. One row covers digital input sources, and the other covers analog input sources. Each test is given a pass (P) or fail (F) grade with the exception of the resolution and scaling tests. An N/A indicates that the AVR in question offered passthrough without processing.

The AVRs are in alphabetic order by manufacturer and in no way represent our preference. Remember, these tests focus only on the video-processing side of these products, which is only one part of the overall package. [In the coming months, look in these pages for full reviews of Denon’s AVR-3808 and AVR-5308, as well as Yamaha’s RX-Z11.—Ed.]