Mick Hardy
The default rendering engines available within Sony Vegas are not suitable for USB or YouTube.

TandemVids tries to choose the best option but the only real solution is to manually create customised rendering templates.

I recommend the Sony AVC rendering templates but you'll need to modify them slightly.

The help file shows how to do this for older versions of Vegas under Home > TandemVids > Tabs > YouTube > Logon and renderers > Customised YouTube templates

The process is a little different for Sony Vegas 12 and 13.

1. Close TandemVids
2. Open Sony Vegas on it's own
3. Insert video and audio tracks
4. Insert empty events into both tracks to enable full functionality of the Render As dialog
5. Select Sony AVC / MVC
6. Select Internet 1280x720-30p
6. Click Customize Template
7. Adjust Frame Rate back to 25.000 PAL if you're not in the US
8. Drop the Bit rate back to 8MB for USB and 4MB for YouTube
9. Leave the Encode Mode set to Automatic
10. Enter a suitable name for the customised template and click Save
11. Back in TandemVids, select the customised template from the list
12. Test the final product and adjust the settings to suit
Mick Hardy attached the following image(s):