Most upconversion DVD Players with HDMI connections work with TVGuardian. So do Blu-ray players when playing DVDs. That said, most of these players require a setting change.
For example, the most common settings for Sony Blu-ray models,
Setup - > Screen Settings -> Output Video Format
Select HDMI and change to 1080i. Other lower resolution settings will work, too, if your TV does not support 1080i or 1080p.
Setup -> System Setting -> Control for HDMI -> Off
Setup -> System Setting -> HDMI: Linked to TV-off -> Off
After changing these settings, make sure to press the INP (input) button on the TVGuardian Remote to cycle to the other INP setting, then back to your Blu-ray or DVD player. This will correct the automatic HDMI switching caused by the factory Blu-ray/DVD player setting.
Different brands may use slightly different terminology, but the basic settings should be the same. You might find these settings under different menu locations, too.
VERY IMPORTANT: The yellow video connection from the player (or any other signal source) provides the CC signal, which the TVGuardian uses to detect profanity. Connecting this is required! Please make sure the Video output is used and not the Digital Audio (these look similar).