Tom – WebEx does a great job keeping the file size low on their proprietary files. We usually see under 50MB for an average 60 minute webinar. But after editing, creating a new WebEx file is not an option since WebEx doesn’t allow this. So, we commonly use MP4, WMV, FLV and other delivery formats. File size will be different for each of these formats and will depend on the settings used to encode them. The content of the slides also makes a difference since busy/detailed slides take more data to reproduce accurately. So all I can do it give you a wide range of numbers that we’ve encountered in the past. Of course, these numbers will change as time passes and video codecs improve, but it might be useful to you.

For a 60 minute web conference at a resolution of 960×720, we’ve seen delivery file sizes as low as 25MB and as high as 250MB. FLV and WMV are usually pretty compact since the codecs we use do a great job with text and static information. But if the program is a screen share, or some other presentation that has lots of movement and detail, these files can also get rather large since we will increase the data rate to accurately reproduce the content. MP4/AVC, on the other hand, tends to yield the largest file sizes from the get-go. I think this is because the codec was originally designed for motion video (anyone want to set me straight on this?). In our experience, it doesn’t do a very good job with static text. To get around this weakness, we have to raise the data rate quite a bit (no pun intended) to keep text from distorting. I’ve seen QuickTime .MOV files that rival the smallest WMV and FLVs, but at risk of giving MAC users a heart attack, I have not experimented enough with MOV to find the best codec for the job. If anybody has any suggestions, I am all ears.