In Use - Mystery Glitches
DVDs are recorded in a high quality MPEG2 digital video format. Unfortunately the best available video connection on the DX2 is an analog S-video port. S-video is better than a standard composite connection (which is also analog) because it is capable of transferring a video's brightness information separately from its color information. This allows S-video to transfer a higher-bandwidth signal from the original video to your monitor than a standard composite connection, which combines the color and brightness signals.
But even though S-video is capable of an improved picture, it remains an analog signal. Since DVDs are digital, the content must be converted to analog as it passes through the S-video connection. Every time you transfer a video from one format to another the "generation" causes a loss in the integrity of the resulting copy. Small details can be lost with each conversion and, therefore, each new generation looks slightly worse than the last. It's not unlike a photocopy. The first photocopy of an original might look pretty good, but if you keep making copies from copies, the flaws soon become obvious and distracting.
If I count a "generation" as an analog-to-digital, digital-to-analog or digital-to-digital transcoding conversion, the output of the DX2 is a second or third-generation copy from the DVD original (Gen 1: DVD to analog output; Gen2: DX2 A/D conversion; Gen 3: (Optional) DX2 digital transcoding to final output format).
Updated 7/26/2006 A small snag in the capture process with the DX2 is that the video will occasionally become very pixilated for a few frames and then revert back to normal. The pixilation is not extremely noticeable, especially when viewing the video on a low resolution standard definition television; however, it can get a bit annoying on a higher resolution display. I found a reference to what appears to be a PCI TV tuner reference design using the GO7007SB as an encoder. It indicates that older versions of the GO7007SB were prone to jitters and mosaic artifacts. So while it's not the same device, this might explain the trouble I was having with artifacts in my captures.
Figures 7 and 8 illustrate the problem during a DVD capture. The source was a standalone DVD player using the S-video connection being recorded directly to a recordable DVD. However, the phenomenon does not seem to be limited to direct-to-DVD recordings or any specific compression format. I kept an eye on CPU usage while capturing video in all of the available file formats and recording sources and it did not exceed an average of 45%. So over-taxing the CPU (Table 1) does not seem to be the cause of the pixilation.
Figure 7: Example of image pixelation glitch (click to enlarge)
Figure 8: A few frames later, the image becomes clear again (click image to enlarge)
|Table 1: Test Computer|
|Motherboard||MSI Platinum K8N Neo 4|
|CPU||AMD Athlon 64 3800+|
|Memory||2X 512 Corsair PC3200 (1024 MB)|
|Video Card||Geforce 7900 GTX|
I also noticed that the audio sounds a little shaky while the capture is running. It turned out that the audio shakiness is normal (according to ADS Tech) and won't affect the final product.