The digital TV function on the phone would likely take a significant amount of battery life away from a full charge. There's no official estimation on the battery life when using specific applications, so it would be hard to pinpoint a figure that I could promise.

I have a phone with a similar battery, and while I haven't run it from charge to discharge using the TV function, I can say that my tal-time is greatly reduced, and a charge would be necessary if I watched it excessively.

If I had to guess, I would recommend that you'd get about an hour or more as a pure, undiluted guess. But do some research online prior to purchasing, read the reviews and ask the questions from users who have the phone. If nothing else, go to the store and ask if you can test it to see how long it goes - that would give you a reasonable expectation of the battery's ability to keep up with your needs.