Reduce file size and keep reasonable image quality

[digifilm]

I shot 15:11 min of video with the Canon Vixia HF 21 in SP mode. The file size is 925MB. I edited it using Corel Video Studio Pro X3 and saved it as mpg. The file size is till 896MB. I tried a number of conversion programs (Any Video Converter, AVS4You, iMovie) to try to reduce it down to as small as possible but the quality is not so great once it is down to below 20MB. Does anyone has any suggestion?
Can I reduce the initial file size to begin with?

[zoobie]

you could try saving it as another codec besides mpg like h264/mp4
how will it be viewed?

[guns1inger]

I tried a number of conversion programs (Any Video Converter, AVS4You, iMovie) to try to reduce it down to as small as possible but the quality is not so great once it is down to below 20MB.

1. Did you try any decent converters ?
2. 20 MB ? You are kidding, right ?

Seriously, 15 minutes in under 20 MB ? Even with H264 you would have to accept a pretty low resolution in order to keep reasonable image quality. You should also look carefully at the audio and perhaps use AAC at around 96kbps stereo.

[digifilm]

It would be uploaded to YouTube and/or Facebook. Any decent converters you can recommend? I am saving the final video as MP4. The bitrate has to be below 100 in order to get the size below 20MB but the quality is not so great. I want to try MSU codec but VirtualDub can't read the input mpg file. What other applications can use the MSU codec?

[manono]

It would be uploaded to YouTube and/or Facebook.

You're not making any sense. You want to wreck the quality before then allowing YouTube to degrade it even more? The usual procedure is to upload a high quality video before YouTube gets its grubby paws on it. That way the end result might be the best possible.

The MSU codec is a lossless codec and will produce enormous file sizes.

The bitrate has to be below 100 in order to get the size below 20MB

What's so special about 20MB?

[dylz]

I would encode to mp4 at a lower bitrate and cut into parts (part1,part2....).