I used Handbrake to attempt a conversion of a dv avi file to m4v. The source is 13GB, the output is 23GB. I set the Constant Quality to 100% and it did warn me that the output would be larger, but that's not an issue for me.

However, only audio came through, no video. There were no obvious errors and when I left it for the night it was 23% encoded.

Thanks.