Music recording and post production for TV is definitely a growth area, with the vastly increased number of channels and outlets for programming. Whereas once the equipment to do this work was prohibitively expensive, it is now practical for home and project recording studios.
Let's suppose you are doing post production and adding sound effects to a video. An instance could be a door slam or a gunshot – just two examples out of an infinite range of possible sounds. In both of these cases it is essential to 'spot' the effect very accurately to the video. In fact the sound has to be in the right place to an accuracy of a single frame (1/25th or 1/30th of a second). Some would say an even greater accuracy is required.
Now if you watch any television at all in this digital age, you will notice that sync is frequently less than perfect (it didn't used to be that way with analog, but this is progress for you!). One of the causes of this is inaccuracy in identifying the correct frame to spot the sound effect to.
In high professional circles, a TV program will be delivered to the post production suite on a Digital Betacam tape. However, since a Digital Betacam deck costs in the region of $50,000 this is not practical for all levels of production.
So you might find the program you are working on delivered to your studio on a DV tape, or even a VHS. In either case, the images will be accompanied by timecode (digital for DV, on the analog audio track for VHS) that will identify every single frame with a unique value in terms of hours:minutes:seconds:frames.
The next step would typically be to digitize the video into a digital audio workstation such as Pro Tools. This is where errors can arise. Even with modern technology, it is often impossible to be sure that every single frame is transferred, and that the timecode display you see on the screen is 100% accurate.
The solution to this is 'burnt-in timecode'. With burnt-in timecode, the tape is recorded with the timecode values inserted into the video image so you can see them in the picture. When you copy this across to your DAW, obviously the timecode values will transfer too, and since they are part of the image, they are guaranteed to be correct. If it happens that a frame was dropped during transfer, then subsequent timecode values will still accurately identify every frame.
Burnt-in timecode is simple and works well. In an uncertain digital world, it is one thing you can still rely on.