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Video compression settings

posted Jul 15, 2009, 6:48 PM by Unknown user   [ updated Jul 16, 2009, 6:16 PM by Eddie Woo ]
I decided that the video file was still a bit too big. It was published under the 'Email' setting, which gave a reasonably small file size. So I tried to publish it for playback on the computer. This allowed for the choice of the final file size, which I set to 4MB, 5MB & 6MB (any larger & it was not worth it, as the first setting gave 5.75MB; any smaller & the playback area would be quartered, & it was small enough as it was). These gave the file sizes of 2.47MB, 3.01MB & 3.47MB.
It seemed that the only difference between the three were the bit rates, but the difference was not that noticeable, so the larger two will be discounted. (There were also differences between data rate & total bit rate [under the 'Video' division in the 'Details' tab in Properties. Both had the same number for all four videos].)
When I checked Properties, the frame rate of the video file I first made (with the 'Email' settings) was shown to be 25 frames per second, & the audio bit rate was 128kb. The smallest of the other three files was shown to be 12 frames per second & had an audio bit rate of 48kb.
Even though the frame rate was greatly reduced, it was only really noticeable at the part with the student writing Japanese characters (the speed of which I doubled, so there is no surprise there). That part was very jerky, but the rest of the video was alright. Even the part where the Japanese class was jumping up & down was not that bad for the file size, which was quite surprising.
Although the original video of almost 6MB was processed quite easily by my computer, I am not sure about other end users. Either way, I decided that this new video was of a reasonable quality for its file size (less than half of the file uploaded earlier!), so I replaced the original one with this instead.
I asked Amy if my video took a long time to download for her, & she said that it was took 4 minutes. I am not sure if the video she watched was the old or the new file (I know she watched the old file, but I am not if she critiqued that or the new one). Either way, if it took that long, then I guess changing the file was a good option.
There was also communication with participants when I found that Amy's videos did not work, but they work now.