Quality: A Formula of Bitrates and Pixels (Part 1: Bitrates & Compression)
When it comes to video, one of the biggest concerns is the quality. It’s a struggle every videographer faces; and rightfully so. The quality of the video can determine whether or not the message of your video is conveyed. If the quality is too low and your video is pixilated, jittery and full of glitches, how can your audience understand what your video is about? On the other hand, the quality of the video may be the best in the world, but if your two minute video is 50mb in file size, you’re going to lose your impatient audience that doesn’t want to wait for the video to download. What it all comes down to is the relationship between quality & file size, and finding that sweet spot in between. Simply put, it’s a game of “what can I get away with?” Let’s dig into this a bit more and get a little technical.
Compression/Format/CODEC
The first thing to decide is what format do you want to output your video in? For example, do you want to create a QuickTime (.mov) file for people to download or would you rather produce a flash video that’s embedded on a webpage? The codec [compressor/decompressor] determines the type of compression used. For example, a QuickTime file using the lossless “animation” codec will produce top notch quality but with an extremely large file size. Whereas a QuickTime file using the “H.264” codec will provide a decent level of quality with a much smaller file size since the “H.264” codec is aimed at web videos and the “animation” codec is aimed towards animation artists and high quality motion graphics. It’s important to explore all the formats and codecs that exist to discover which combination best suits your video. For the sake of this article, I’m going to deal with video designed to be played within a flash player that’s embedded on webpage.
Note: Currently there are two popular types of video formats being widely used with flash players; flash (.flv) and MPEG-4 (.mp4). For the purpose of this article, I’ll be using the MPEG-4 (.mp4) format as it provides a better compression (in my opinion.) The MPEG-4 file will be used inside a flash player that will be embedded on a webpage.
Bitrates = Quality Control
Think of the bitrate of your video as the quality control. A higher bitrate means a higher quality. Simple enough, right? Well not exactly. While bitrate determines the quality of your video, it is also dependent on the contents of your video. Videos with lots of fast motion and animated graphics require higher bitrates in order to maintain high quality whereas videos with little movement can get away with a much lower bitrate. This is due to the amount of detailed movement occurring in the video. For example, a music video containing several animated motion graphics, special effects and CGI is going to require a much higher bitrate than say a documentary containing mostly talking heads and interviews. The key is to analyze your video and experiment with the bitrate settings. Since each video is different, there really is no set rate that will work well for all videos. The same goes for audio bitrates. In my experience, unless the soundtrack contains a vast array of musicality that you want to emphasize, there’s no reason to use anything higher than 96kbps. Most of the time the videos I produce will contain a voiceover track with soft background music, and I can usually get away with using a bitrate of 64kbps without noticing a quality loss. Everything here boils down to trial and error. You’ll have to play with the settings and get a feel for the balance between quality and size. Familiarizing yourself with bitrates will save your neck in the long run (not to mention lots of time and headaches!)
Note: Most video encoding applications give users the option to use either a constant bitrate (CBR) or variable bitrate (VBR.) A constant bitrate is a set bitrate used throughout the entire video whereas a variable bitrate allows the user to set a maximum and minimum bitrate in which the application assigns to parts of the video depending on the movement and detail. While both options contain pros and cons, for the nature of this article, I’ll be dealing with constant bitrates (CBR.)
Bitrates and compression aren’t the only factors involved with determining quality. In my next blog, Part Two: Physical Dimensions and other Tricks, I’ll discuss a few other key factors that effect quality and file size. Until then, I encourage you to experiment and play around with these settings. You’ll save yourself tons of time in the long run and make your videos look better too! Good Luck!

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