Review: Plextor ConvertX PX-M402U Digital Video Converter
Posted Apr 2, 2004

Plextor's ConvertX isn't the first USB 2-based A/D converter box we've seen or reviewed here—ADS' USB InstantDVD holds that honor—but it brings some interesting new features to the table. First and foremost, it's the first DivX-certified consumer hardware capture device, and delivers real-time DivX and MPEG-4 encoding. What's more, the ConvertX is also priced lower ($159) than devices that also offer MPEG-2, but not MPEG-4 or DivX.

It's sleek, shiny, and lightweight, but beyond that it doesn't look like much. It mostly resembles a bedstand clock-radio except instead of the time/frequency LCD it has composite and S-video connectors and two status lights on one side and a USB port on the other. Of course, the real action happens on the inside: true to its name, the heart of the ConvertX is a real-time hardware MPEG encoder that in this latest version adds support for the MPEG-4 and DivX formats increasingly popular in Web and portable-device video delivery and available in several recently announced DVD players. The box includes an NTSC/PAL decoder which enables you to capture video from PAL video sources and convert them to NTSC for viewing on North American televisions. Inside you'll also find, naturally, a USB 2 controller for connection to high-speed USB 2 ports.

Plextor's never been one to skimp on software (their CD-R HW/SW bundles are always among the most generous in the industry), and the ConvertX ships with everything you need to get going: USB 2.0 drivers for quick-and-painless installation [visit for the latest upgrades], and two InterVideo tools, the excellent entry-level DVD authoring software package WinDVD Creator for capture, clip-trimming, menu-building, and recording; and WinDVD, the company's industry-leading software PC-DVD player.

The Numbers Game
Once you get the ConvertX installed and up and running, you'll need to connect an analog video device via the composite or S-Video connectors (I attached a VCR via composite) and select the appropriate connector in WinDVD Creator (default is S-Video; you'll be prompted if something is amiss). Next you set capture parameters, which is where it gets interesting. For MPEG-2 you get several choices, ranging from 6Mbps High-Quality (HQ) to 4.5Mbps Good Quality (GQ) all the way down to lowly EP, which promises 4+ hours of video on a 4.7GB DVD. All these choices are 640x480 full-screen; you can also select VCD, which is 352x240 MPEG-1.

That's all pretty familiar. What you also get are a number of choices for MPEG-4, beginning with selections for the MPEG-4-based DivX consumer video format. Select DivX HT (home theater) for highest quality, full-screen; or DivX Portable for 352x240 low-bandwidth video tailor-made for the growing number of PDAs and other portable video devices offering DivX support. You can also choose MPEG-4 HQ and MPEG-4 GQ.

The magic of MPEG-4, being a newer and more efficient codec than MPEG-1 or MPEG-2, is comparable video quality at lower bit rates and lower filesizes. Our tests bore that out, for the most part. Capturing video from several different VHS sources, but using identical 5-minute, 2-minute, and 1-minute clips for tests at those durations, results were visually very strong and comparable in the DivX HT, MPEG-2, and MPEG-4 HQ and GQ formats.

For the two-minute file, for example, filesizes came in at 67.6MB for MPEG-2 HQ but only 61MB and 63.4MB for DivX HT and MPEG-4. That doesn't sound like much of a difference, but project it over, say, 60 minutes of video, and you're looking at 180MB difference between the MPEG-2 HQ file and the DivX HT. The differential was even more striking at the GQ (good quality) level. While the video output was comparable between the MPEG-4 GQ file and the MPEG-2 GQ file, the filesize differential was nearly 18MB. That may not be typical (although the VBR encoder in the ConvertX averaged nearly the same video bit rate for the HQ as the GQ MPEG-2 files in several tests on different sources), but project that two minutes to a 60-minute clip and you're looking at 540MB. (Data on the video was collected using the GSpot Codec Information Appliance and a utility called ReMPEG2.)

Video playback quality was excellent in all five cases when played back in WinDVD. As for the partial screen stuff, the DivX Portable clip looked substantially better than the MPEG-1 clip, and the filesize was quite a bit smaller: 13.1MB for the two-minute DivX Portable compared to 21.25MB for the MPEG-1 VCD clip.

Old School
As many of you may recall, these nifty USB 2 converter boxes used to do one thing, in the main: capture analog video from VHS, convert it to MPEG-2, and launch a DVD authoring tool that would let you make a basic menu and burn it to DVD. In addition to all its MPEG-4 capabilities, which obviously open the ConvertX to all sorts of new conversion, output, scaling, and delivery possibilities, the ConvertX package also includes solid DVD creation capabilities.

When you move into Edit mode in WinDVD Creator, the software prompts you to detect scenes, which you're well-advised to do when you've captured that much video. Testing the software on my 3.0gHz Pentium 4 Gateway 510XL testbed, this process still didn't go all that fast—probably about 12 minutes all told, albeit with other applications running. Another user might easily interpret that as lightning-quick, but I guess I'm just impatient.

You can also set thumbnails here, split and combine scenes, and trim start and end points as needed. Then it's on to a nice and reasonably flexible DVD authoring application, without a lot of menu templates, but a nice title/chapter menu structure all the same.

Interestingly, you get a little more bit-rate flexibility than in authoring mode when you do direct-to-disc recording, which is something you can do "live" via the ConvertX box and WinDVD Creator's very handy Disc Manager. It functions very similarly to "direct-to-disc" recording via FireWire, except with hardware encoding. You can also record an editable disc, which means you can capture directly to disc then grab the DVD-compatible MPEG-2 files off the disc and add DVD chapter menus at a later date.

I made three different DVDs during the evaluation period for the ConvertX, upgrading three different VHS-only (to my knowledge) titles to DVD. The first of the three had some audio-sync issues, but audio-sync was perfect in the other full-tape-to-DVD tests as well as all the shorter-clip tests done to compare MPEG-2/4 quality.