I have a Pioneer 460, so can answer your question.
The 460, like all other Pioneers with USB, cannot actually do much of anything with that connection. Everyone expects they'll just plug in a USB hard drive or thumb drive and these units will just happily play them, but that ain't the way the DVD recorder ball bounces. Unlike many dedicated DVD players, which will read and play anything you connect to their USB sockets, DVD recorders are always crudded over with restrictions under the guise of "discouraging copyright infringement." There have been a handful of exceptions, but most of the major brands and models of recorder work like the Pioneer 460, as follows:
The USB connection cannot be used as a direct playback source for video. Period. So if that's what you urgently want to do, forget it, and go buy a more flexible and suitable DVD player or discless media player interface for your TV.
The USB connection cannot be used as a direct playback source for audio files (MP3s).
The USB connection CAN be used as a direct playback source for still image (most JPEG files) stored on a thumb drive, HDD, or connected camera.
The USB connection CAN be used with a PC keyboard for entering title names on recordings.
Compatibility with video files stored on external USB drives (or on data DVDs or CDs) is somewhat limited. The Pioneer 460 can only play AVI format files and some variations of DiVX files. It will play both NTSC and PAL video files, but certain off-spec PAL files won't play and the converted PAL signal can only be viewed on your television (if you try to copy it, the recording device won't "see" the signal). MP4, MKV, M4V and H264 are not supported at all.
Video or audio files from USB devices MUST be copied to the PIoneer 460 hard drive in order to play them. To do this, connect the USB device and then go to the Home Menu and select "PC Video." When the submenu appears, choose "Copy Video File from a USB Device." A file list will appear, and you can choose which files to copy to the Pioneer HDD. Once copied to the Pio 460 HDD, they don't appear in the normal Navigator window: you choose to view them in a separate file browser by going to Home Menu>PC Video>VIEW Video File On The HDD." The same procedure applies for MP3s and JPEGs, you just choose the appropriate browser in the Home Menu.
Again, be aware that a lot of video files just won't play even after you copy them to the Pioneer HDD: there's no way of knowing in advance, since the unit won't allow playback attempts directly from the USB source. Of the many files I download, perhaps 1 out of 5 can be played on DVD/HDD recorders.
Things are a bit easier if your video or audio files are stored on a DVD or CD data disc. The 460 is equipped to play files directly from loaded discs, which enables you to check if they're worth copying to the HDD. If choosing a video file on a disc results in a black screen, or audio with no video, then you know it won't work. Audio files and JPEGs that are off-spec will display in the 460 file browser with a yellow question mark triangle icon, indicatiing they're not compatible.
Regarding video cameras, connecting one to the DV input (FireWire) will allow playback from the camera. More recent cameras that connect via USB instead of DV/FireWire are treated as if they were thumb drives: video must be copied to the 460 hard drive before they can be played.
All of the above applies to the Pioneer 450, 550, 650, 460, 560, 660 and LX models. The 540, 543, 640, and related Sony clones like the RDR-HX780 are similar but will only play DiVX/AVI from a loaded disc (they cannott copy the video files from disc to their HDD). The x40 series does not recognize USB keyboards, the Sony 780 might accept one.
Specific instructions and details can be found beginning on page 85 of the 460-560-660 user manual. Note the true functionality of the "USB file transfer from a laptop or PC" feature is grossly misrepresented: the feature almost never works. There is a bug in the Pioneer firmware that restricts recognition of USB-attached PCs only to those running a handful of particular Windows XP service updates. Some users succeed, most don't. I have not heard from anyone who attempted connection to a Windows 7 PC, nor have I tried it myself, so can't advise on that point.
Edited by CitiBear - 10/12/12 at 6:16pm