QuickTime is Not a Codec: The Basics of Media Files

Danger: This post is pretty old and may not be relevant anymore.

If one more person answers “What codec is it?” with “Quicktime,” I’m going to lose my shit.

QuickTime is not a codec. QuickTime has never been a codec.

Seriously guys, it’s 2012. We have fifty new cameras released every month, all of which shoot to a myriad of file-based formats. Get your shit together and stop wasting my time.

The Basics of Media Files

Think of media files as boxes full of stuff. Good stuff, like kittens and PSY.

a terrible photoshop of Psy in a cardboard box with some kittensThis is the best explanatory image of a media file you’ll ever see

The box itself is the* file type* – this can be MOV, MP4, MXF, all kinds of different things. We also call this the *wrapper* or *container*. Easy way to tell: it’s normally the same as the file’s extension (.mov, .mp4, etc.).

Inside that box are two things: metadata and essence. Essence is the actual media, but it’s generally useless on its own. Metadata is what makes it useful – this is data that describes the content of the media file, allowing software to interpret it properly. This can contain all kinds of info depending on the file type, but it usually at least includes resolution and framerate.

But* essence needs a bit more specificity. You can’t just throw “video” into a file – it has to be encoded in some way. Even uncompressed video is still encoded. This is done by a codec, *which encodes the essence data for storage in the file, and also decodes it for playback. So when we’re talking about *codecs, *we’re talking about which encoder/decoder applies to the media essence inside the file. Common examples of these are H.264, DNxHD and ProRes for video, and PCM and AAC for audio.

Real-World Example

Confused? That’s fine. The main takeaway is that there are different components that make up media files, and describing them correctly will save everyone a lot of headaches.

Take a look at YouTube’s specifications. You’ll notice that they specifically describe all aspects of the media files they’ll accept, in proper terms. There’s some more advanced stuff in there than I cover here (namely, codec-specific encoding options), but the core description of a media file is covered:

  • Container: mp4
  • Audio Codec: AAC-LC
  • Video Codec: H.264

Do you see now why answering the codec question with “QuickTime” makes no sense? Not only is QuickTime not a codec, it has no place in any description of a file – it’s just the software used to play the file.

Get It Right

Hopefully this has been an enlightening read for some, and preaching to the choir for most. This stuff is the most basic information about materials we use daily; there’s no excuse for not getting it right.

So the next time someone answers you with “QuickTime,” please berate them into a coma. You’ll be doing us all a favor.