No subject

help most, though if such a thing exists is still unclear.
Though since you say it is an encoder card (by which I assume you mean
this thing has an actual hardware encoding chip), there are two obvious
points:
1) Most USB encoder cards only have an encoder because they only support
USB 1.1. You can't transfer 640x480x25 fps over USB 1.1, it's simply
impossible. Getting a USB 2.0 device helps there, though it can't fix
the fact that USB in any version sucks for actually transferring data.
2) Thus you should find out how to make this thing encode, having
to transfer less data over USB will always save more than the decoding
will cost.

Note that according to the output it is your webcam that supports
encoding (only JPEG, and MPlayer does not use it), to the TV card...