What Is Transcoding

The process of converting a piece of media from one codec to another is called transcoding. Most video container file formats can support a wide range of different codecs. So, for example, you can have a .MOV file that uses the H.264 codec, and you can also have a .MOV file that uses the Avid DNxHD codec. If you shoot footage with a camera using H.264, drag it to your desktop, and then convert it to DNxHD to work with Avid Media Composer,
you are transcoding your original media . The file itself will still be a .MOV file, but you will have fundamentally changed your media.

Transcoding can be a hardware-based or a software-based process and whenever you move
digital video around, you run the chance of transcoding your media. Transcoding isn’t necessarily
bad; in fact, it’s often necessary and beneficial, but you should make sure you are not
unintentionally transcoding your media to a lower quality codec.

So how and when does transcoding happen? The first way has to do with how you move media
from your camera to your computer. If you are dragging and dropping files from a disc or
hard drive to your computer’s hard drive, you are not transcoding. But if you are using a cable
running from your camera or videotape deck to a video input on your computer or video card,
then you need to be careful. If you shoot HD, then you need to make sure that the chain of
connectors and cables between your camera and your computer is all digital. If your camera
has an analog video-out connector, such as S-video, then simply by sending your video out
through this connector you are transcoding it into an analog signal. Then when it gets to your
video card or connector on the computer, it is being transcoded back into a digital signal. It’s
true that you may not see a huge difference in the resulting image, but it’s better to avoid
transcoding your media more often than is necessary for your workflow.