The H.264 codec (that is a part of MPEG-4 advanced profile) has become the main-stay of high definition video output, over the last decade, alongside other codecs like VC-1.
For high-definition output, you essentially have two major resolution targets, 720p (1280x720 or approximate), or 1080p (1920x1080p or approximate).
The two major video containers that have established themselves across the *cough* high-def downloadable video content arena, are basically Matroska (MKV), and ISO MPEG-4 (aka MP4).
AVI is not in this list, because AVI's data structures are nominally signed 32-bit, and thus do not scale out well past 2.1GB of data. This would drastically limit the amount of video data that can be held in an AVI, so it's usually relegated to low resolution content, now.
If you use a tool, such as MakeMKV, to make a backup of blu-ray content, you'll see that a full quality rip of a single blu-ray movie (just the movie, not the other features, menus, etc.), will vary from approximately 20 to approximately 40 gigabytes in size. This translates roughly to a video bandwidth between 36 megabits per second, and 54 megabits per second (max, as defined by standard.)
This should give you a solid ceiling for high-def content.
Most "downloadable" content from various sites, however, will be significantly curbed, to make the downloadable size much smaller, so you'll typically see good copies of a movie from 6 gigabytes to 12 gigabytes in size.
Scale accordingly. Hope this helps.
-Thom
