How To: Video Compression for the Web
By Ron Dawson
Perhaps one of the more challenging issues photographers entering the world of video face is compression for the web. It’s one thing exporting a jpeg. When it comes to creating videos for the web, it’s a whole different ballgame. There are so many different considerations.
No doubt the majority of you are editing high definition videos: 1080p (1,920x1080) or 720p (1,280x720). For a majority of the work I do, I edit in 1080p then export at 720p for the web. If the site I’m uploading to will support it and the visuals would benefit from a higher resolution, I may export a 1080p file.
Bits and Bytes
The next decision, and perhaps the most important, is what data rate to set. Most of the data rate figures you see will be in megabits per second (mbps). The capitalization is important, because if you write MBps, this traditionally stands for megabytes per second, not -bits (eight bits make up one byte). Don't be surprised if you ever come across an article using MBps, but meaning mbps. You'll know by the size of the number. Here are some common numbers to give you perspective.
● The .MOV files in popular Canon DSLRs are compressed at approximately 45 mbps.
● The .MOV files in some of the most popular Nikon DSLRs range from about 14 mbps to 24 mbps (depending on the quality setting)
● The popular Apple codec ProRes 422 is about 145 mbps
● Standard Definition DVDs range from 4 to 8 mbps
Most compression programs will give you the option to do constant bitrate (CBR) or variable bitrate (VBR) compression. CBR will compress the entire video at the same rate. If you're not concerned about file size, this may be a good option as it's faster and takes less processing power. With VBR, the computer will compress different parts of the video at different rates (you will enter some target or average rate). So high motion parts of the video will get a higher rate than sections where there's no motion at all. That way you can better optimize the video.
There are a few different formats to consider when exporting for the web: mpeg4 (which includes .mv4 files), mpeg2, h.264, wmv, etc. These are all different codecs. Codec is short for "compression-decompression." It's the algorithm used by the computer to compress large video files into something more manageable. All major video sharing sites will accept all the popular formats. So whether you're a Mac or a Windows person, the format you export can yield a video people will be able to watch, regardless of operating system or browser. It should be noted that .MOV does not represent a codec. It's the suffix for a QuickTime video, but that video could be any number of codecs. You can have an h.264 .mov file, a ProRes .mov file, an MPEG-2 .mov file, etc.
The Perfect Recipe
There is no "best" combination of settings. It all depends on things like audience, upload destination, length of video, and such. Here's my usual recipe (using Apple’s Compressor):
○ AppleTV codec, h.264
○ 1,280x720 resolution
○ 4-7 mbps (depending on varying factors)
○ Frame rate (source, which is usually 24 fps)
○ 128 kbps
Video compression is two parts science and one part art. With practice and time you’ll come up with a recipe that works best for you and your clients.