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Physical Dimensions

Bitrates aren’t the only factor involved with determining quality and file size. The physical dimensions of your outputted video have a direct relationship with the file size. Read that again. This means that a video displayed at 640×480 is going to be much larger in file size than a video displayed at 320×240. Also, a video at 640×480 will require a higher bitrate than a video at 320×240.  This brings up something new to think about. What dimensions should your video be displayed at?  Again, this comes down to a lot of trial and error.

Let’s look at two extreme examples:

1)    A video containing highlights from a football game, recorded in DV (720×480.)
2)    a software tutorial screen captured at 1024×768

First, let’s analyze the football video. We know there’s going to be a ton of movement and motion graphics highlighting the plays. Therefore a high bitrate will be needed. Also, since there will be graphics to highlight the players along with a commentary, displaying the video at large dimensions probably isn’t necessary and by lowering them, we can help decrease the file size. I’d probably aim for 400×300 or 320×240 using square pixels and a bitrate somewhere around 600-900kbps as a starting point.

Second, let’s look at our tutorial video. We’ve got a 15 minute tutorial on using Microsoft Excel containing lots of highly detailed graphics and small text. Since the ability to read the small text and graphics is crucial, shrinking the dimensions of the video isn’t a practical method for keeping the file size down. Our best choice is going to be the bitrate. As a software tutorial, the video contains very minimal movement. Other than some mouse movements, typing and a few scrolls, there isn’t any real motion involved.  I’d start with a bitrate around 900-1000kbps as a starting point and go from there.

So that’s a couple of the extreme scenarios you might face. Regardless of the video content and dimensions, I always try to keep my videos under 5mb per minute. For broadband users, this seems to be very tolerable. Again, play around with the settings and get to know the relationships they have with each other.

Other Tricks

The bitrates and dimensions of your video are your bread and butter for determining the quality and file size of your video. There really isn’t any special tool out there that’s going to magically give your video better quality with a smaller file size. If you’re willing to spend a bunch of bucks, you can buy fancier encoders that can contain some better codecs, but it’s usually very hit or miss. Instead, when I’m stuck with a large video file, I like to trick my audience into thinking it’s a smaller file size. What I mean by this is there are some methods that can be used to make it less painful for your audience to wait while your video downloads.

Before I get into these, keep in mind that I’m speaking about a video that’s embedded in a flash player on a webpage. This does not apply to videos that are downloaded onto the user’s hard drive.

• More than Less – This one is kind of a no-brainer. If you’ve got a very long video, say a tutorial, demonstration or presentation, break it up into sections. If it’s a 60 minute video, try breaking it up into six 10 minute segments or chapters. Most people have an easier time with multiple shorter segments, than one long video. Plus, they will be more inclined to sit through it and can easily jump through the video since it’s in convenient sections.

• The Preload - This one’s my favorite and I use this “trick” all the time. Most flash/player encoding programs have an option to use a “preload movie.” What this does is adds a little graphical progress bar to display as your video loads. Generally, you can set the amount of video to load prior to playing it. For example, when I have a longer video or one that’s very large in size, I’ll set the preload to something like “5%.” This means that when a viewer clicks play (or if the video automatically is set to start), they’ll first see a logo or graphic with a progress bar, stating that the video is loading, and when the video has downloaded/loaded 5%, the video will begin playing. The big benefit here is that now there is a little cushion of video already downloaded so the viewer should be able to watch the entire video smoothly without the play bar catching up and causing the video to halt. I mean, let’s face it. About the most annoying thing that can happen while watching a video is having it stop playing because more of it needs to download! This gives you that insurance without losing your audience.

Last Notes

Some of you may be wondering what specific software and settings I use. Well, while I can’t get too specific (since each project differs), I can give some general settings I use on average. Most of my projects are natively recorded in DV (720×480) and brought into my suite as DV AVI files. My projects are edited in the same format and then rendered out as 640×480 QuickTime .mov files (using square pixels) using the “animation” (or sometimes “photo jpeg”) codec. From here the QuickTime (.mov) file is brought into my flash/player encoding software. I use a program called Camtasia Studio. It’s a program I use for screen capturing and recording tutorials, but it also contains a very nice set of tools for creating and encoding flash videos and players. This is where I set the bitrates and dimensions of my videos as well as the preload (if I decide to use one.)  As an example, a recent project I did resulted in a video that was just over two minutes. The video contains lots of detailed motion graphics with text so I only shrunk the dimensions to 500×375 and set a video bitrate at 900kbps with an audio bitrate of 64kbps. I set a preload of 2%. The result was a high quality product video under 15MB. It’s still a little larger than I’d like, but the size was unavoidable due to the detailed graphics and text, which is why the small preload in front comes in handy. That’s just one example, but hopefully it helps!

As always, I hope these blogs provide some insights and useful information. Again, it’s going to take a lot of trial and error to get familiar with how these settings work. I encourage you to experiment and play with each setting until you know it inside and out. I’d recommend taking several short, 10 seconds clips of various content and toying with the settings. Trust me, you’ll save yourself tons of time in the long run (and make your videos look better too!) Good luck!