Set-top DVD recorders, not to be confused with computer DVD burners, have been heralded as VCR killers. Not only can they do everything DVD players can, they can also record TV programming (just like a VCR) and home videos to inexpensive writable or rewritable DVD discs that play in standard DVD players. While we test them for DVD playback just as we would a normal DVD player, we also use a full suite of tests to evaluate recording performance. These include evaluating image quality at various recording settings, seeing how the recorder handles motion, checking its effectiveness making timer-based recordings, and more.

Test environment

Experience in testing DVD recorders and familiarity with the issues and technologies associated with the category are prerequisites for all of our testers.

We don't use a single reference TV to test DVD recorders. Instead, we use high-definition monitors with split-screen picture-in-picture (PIP) capability that have been professionally calibrated and are currently being tested as part of CNET's television reviews. For DVD playback testing, we follow the same procedures we use for testing DVD players.

For our recording tests, we use standardized source equipment: Our VHS source is a JVC HM-DH3000U D-Theater D-VHS player. Our DVD source is a modified Apex AD-600A DVD player. We also use our in-house DirecTV and/or Dish Network satellite feeds to test TV recording capability, including satellite box control (if any).

Our suite of DVDs for testing recording quality includes:

• Video Essentials DVD
• Digital Video Essentials DVD
• Avia Guide to Home Theater DVD

Recording tests

Recording quality still varies among different DVD recorders, though all of them outperform VHS and S-VHS VCRs. Unless otherwise noted, our recording-quality tests are performed on write-once media (DVD-R and DVD+R) as opposed to rewritable media (DVD-RAM, DVD+RW, and DVD-RW).

Resolution

We use the 200-TVL resolution pattern from Avia to determine how much detail a recorder captures on a still frame. We perform this test for each of the recording modes available, since recording modes are the primary determinant of image quality. For example, a mode that allows 1 hour of recording time on a single disc will always have better image quality than a mode that allows 4 hours on a single disc.

MPEG artifacts in motion

We use various DVD scenes, such as Chapter 4 from Monsters, Inc., the Montage of Images from Video Essentials, and other scenes with movement to evaluate how well a recorder handles motion, specifically with regard to MPEG artifacts. These appear as blocky distortions and show up especially in areas with quick movement and areas of intense color. This test is performed for each of the recorder's modes.

A/B source/recording comparison

Using a television with a split-screen function, we look at the original source DVD or TV program and the recorded program simultaneously, side by side. We note any differences in color fidelity, sharpness, noise level, and other problem areas. This test is usually performed with clean, high-quality theatrical DVD releases, such as Monsters, Inc, Finding Nemo, and Star Wars, Episode II: Attack of the Clones. We use the recorder's 2-hour setting for this test.

VHS recordings

With the knowledge that many people use their DVD recorders to transfer home movies from videocassette to DVD media, we evaluate how well a recorder preserves the quality of the original VHS tape. If the recorder has a noise-reduction circuit, or one that supposedly enhances the image quality of a VHS recording, we test its effectiveness as well.

Timer recordings

We program the recorder to begin recording at a particular time from a TV source. If the recorder has VCR Plus or an electronic program guide such as TVGuide or Guide Plus, we test how effective it is with Time Warner Cable's system and/or DirecTV and Dish Network, whichever is appropriate.

Compatibility

For each type of write-once and rewritable DVD media a recorder supports, we record onto blank media from at least two different manufacturers, then play the discs back in DVD players we are also testing at the time. If any of these recording/player combinations work improperly, we note it in the review.

Specialized tests

Depending on the type of recorder we're evaluating, various other tests are required. Here's a brief rundown of the more common specialized tests.

FireWire

This test applies only to recorders with FireWire (also known as IEEE 1394 or iLink) jacks. Using a FireWire camcorder and a MiniDV source tape, we evaluate how well the recorder handles these sources by using the recorder's 2-hour mode, then playing back the resulting recording and the original source side by side on a TV using the split-screen function.

Hard disk recorders

If the DVD recorder includes a built-in hard disk, we test the speed at which it dubs to DVD, the ability to record from any flash-media formats, and any editing capabilities the hard disk allows.

Flash memory

DVD recorders with built-in flash memory ports are tested for how quickly they transfer the contents of flash memory cards to disc and vice versa, if applicable. Also, we look at how user-friendly the recorder's interface is for handling a card's contents.