Containers, Codecs and Video Formats Oh My
“What is the difference between containers, codecs and video formats and why do video professionals need to know this stuff?”
HELLO! I’m not an engineer or a programmer, why can’t we just leave this technical jargon for editors to figure out? As motion picture professionals in a digital age we can no longer ignore that the singular chemical process of film has been replaced by non-linear data. Figuring out this information can be daunting so let’s break it down into three sections. We’ll define containers, codecs, video formats and explore what they do and why this information is useful to video Producers, Camera Operators and Editors.
Let’s get the lingo straight. A container, sometimes called a wrapper, is code that does what it sounds like it does. It “contains” or “wraps” other code. Broadcast Engineering put it best in their article Digital File Formats,“Special file formats called containers are used to combine or hold the audio and video elements (files) within one file for convenient storage and transport”. Codec is the compression & decompression of large files in a uniform way so that your video and your audio plays the same way every time. Co = coder+ DEC = decoder or compression + decompression. To find out more about codecs check out this Wiki link. Digital video formats are often codecs within other codecs. For example XDCAM HD (the video format) is an M-PEG 2 Long GOP video codec that has an MXF container. According to aforementioned Broadcast Engineering article “MEPG-2 is a compression codec for digital video but is also a container when the audio is combined with it; the difference is in the file extension used.” GEEZ!…what are these engineers trying to do to us?! Why can’t they keep apples, apples and oranges, oranges? But wait this is a perfect example; an apple is a fruit and it can be the color red or green. An orange is also a fruit and orange describes the color and the type of fruit. This is a prime reason why wrappers, codecs and video formats can be confusing. Stay with me…
Now that we know the names and definitions lets find out what containers, codecs and video formats do. Simply put, video formats, containers and codecs are all bits of code; ones and zeros that tell a device what to do or how to react. The code is like your wife at a dinner party. She first explains what to wear, then goes on to tell you the background of everyone attending . Finally, after too many glasses of wine, she puts the keys in your hand and says while batting her eyelashes “Can you drive home honey?” Code acts much the same way. Video formats is the code that tells the camera how to capture what the lens sees. It tells the video and audio how to look and sound (like your wife telling you what to wear). Once acquisition is complete the container will keep the audio, video and metadata together for transport. For example, when files are transferred from a P2 card to a card reader then to a hard drive for editing, the footage is imported and edited with your chosen NLE. A new codec is prescribed depending on your deliverable. For example writing your video to Blu-ray disc using M-PEG 2 or compressing your project for the web in H.264.
So what does this mean again? The digital video/ digital cinema game is decided by what companies can come up with the best imagers to capture footage and the algorithms that compress that footage, transfer and decompress, recompress and then decompress again. We are all familiar with the phrase garbage in garbage out. As video production professionals we need to assess the subject matter, think about what acquisition format meets those requirements and what deliverable will best keep your message intact. For example if you are recording a football game a video format and compression that relates well to movement is important. Perhaps you are capturing the fibers of a tapestry while the artist is sitting at their loom, then the sharpness of picture and color definitions are key deciders on your camera and compression choices.
Whatever the scale or cost of the project remember, all those ones and zeros that make up containers, codecs and video formats are working behind the scenes to deliver the project our audience sees and interacts with.