Why Keep Online Video Small?
Videos you include on your Web site pose download problems on the most powerful personal computer and the fastest Internet connection. In fact, no one even thinks about recording, transmitting, and playing back uncompressed video full-screen. The bulk of online video you’ll see is compressed, using a three-stage process:
To play back a completely uncompressed widescreen video at 30 frames per second would require a connection with a speed of more than 1 Gb/second, which is more than a thousand times faster than the rated speed of a very fast home or office connection.
Show video in a small window: YouTube recently upgraded its offering and began showing most videos in a relatively generous 480 x 360-pixel window, exactly one-fifth the pixels available on a typical 1024 x 768-pixel screen.
Reduce the frame rate: Although players adapt to the bandwidth available, a rate of 10 frames per second — one-third the frame rate of television — is considered acceptable.
Compress the images: JPEG compression, good as it is for images, works with only one frame at a time, so MPEG video compression is used instead.
MPEG, more commonly known as MP3, takes advantage of parts of a scene that don’t change from one frame to the next, and only encodes the changed parts. Unfortunately, when part of a scene changes very fast, or all of a scene changes fairly fast, there’s often visible distortion in the scene until the compression and decompression can catch up.
Video clips, even on the relatively robust YouTube site, often stall during playback. This is extremely frustrating for users and for you, if the video is on your Web site. Unfortunately, there is so much variation at all points in transmission, reception, and display of online video — from the servers, across the Internet and on the user’s computer — that it’s impossible to give users any quick or certain fix for any problems they experience. Compression helps your video work well on the Web, but to make it sweet, keep it short.
For typical YouTube-style video clips — medium-size 480 x 360-pixel images, harshly compressed, usually grainy and a bit dim — each 15 seconds of video takes up roughly 1 MB. That’s 4 MB per minute. Not too bad a size for a three-minute music video, but that one-hour CEO speech at the annual results announcement is going to take up 240 MB!
If you must deliver a long video, break it into clips. Preface each clip with a brief description. And hope that at least some of your site visitors have the patience to get through all of it.