How to make your video assets playable on different platforms.
Whether preparing a video for storing in a video asset management system or for deployment on a website, I often hear questions about the best setting for video encoding. Often this question is answered with another question, or a series of questions.
Are you being provided with any video specifications? What medium are you encoding the video for? Who is your audience and how will they be viewing it?
It also depends on your method of transferring the video file to its final destination. Do you really want to push a 30 minute uncompressed HD video file through a dial-up connection?
The most important thing to remember when encoding anything is: “garbage in – garbage out”. It’s very important to start with the highest quality video as your source. Archiving your video to DVD video and then encoding from that DVD only adds to the compression artifacts of the final encode.
When you begin to encode, the best situation is when you’re given the exact specifications for the file that you are to provide. If you have the dimensions (how wide and how tall), the frame rate (how many frames per second), the data rate or bit rate (what is the maximum amount of data that can be transferred each second) and the codec that is required (the format to compress the video), all you need is the right encoding system or software with the appropriate codec installed.
If you aren’t given the exact specifications, you need to work with the information you have, and fill in the blanks with educated assumptions.
The most important of the questions is who is the video for and how will they be viewing it. The “Who” part of the question, allows you to make an educated guess on what bit rate to use. Since the bit rate is the amount of data that is delivered to the video player every second, it’s important to know how fast a connection your audience has to the Internet. The “how” part of the question will let you know what codec to use and what type of video wrapper. The wrapper is the document format used to play the video. Is it going to play back as a QuickTime movie, in a Windows Media Player or as a Flash movie? These are just some of the different types of video wrappers.
In the case of storing video in a digital asset management system (DAM), I often recommend storing it in its original source format, but when access to the DAM is only possible remotely, it becomes necessary to encode it as the best quality, smallest file size possible.
When you have an educated guess, the settings you use on a video become a compromise of size versus quality. Even the most seasoned video specialist will use a saved setting as a starting point and then tweak it based on a sample of the actual video.
For example, we recently worked on tweaking encoded videos for some users who had trouble playing them because of a slow connection to the Internet. We found that we could effectively reduce the bit rate from 512 Kbps to 112 Kbps for a lot of the clips and maintain an acceptable image quality. Because most of the clips were talking head videos and there was very little motion between frames, we were able to drop the data rate. If the clips had a lot of motion between frames, or a lot of detail within the frame this drop in bit rate would not have been possible.
In cases such as these, I have found it useful to know beforehand how large a certain video file will be once it is encoded. To help with this, we have posted a video upload/file size calculator. The calculator helps you figure out how much drive space is needed for a video and then how long it will take to upload the video.
Posted by James Burke
Photo by James Burke