It's become increasingly common for movies to contain sections with varying aspect ratios. For instance, the movie The Dark Knight is is sometime 16:9 full frame, and at other times 2.40:1 with letter boxing. This is fine when viewed on a 16:9 (or even 4:3) screen, but if you try to watch it on a 2.40:1 screen you will get simultaneous horizontal and vertical letterboxes. Extremely undesirable.
Currently I use MPC-HC, which has a feature where it is able to analyze the video in real time, detect letter boxing, and dynamically crop the video. This works pretty well, but it's kind of an ugly solution. Are there any video formats that allow meta data like image resolution to change throughout the video?
The problem isn’t the format, it’s the players. Most video codecs store their resolution in an optionally inband header, but the player would need to look for those, reset and reinitialize the decoder, reconfigure the display surface, and continue.
Which make this a catch 22. Most players do not support this, so most files don’t try to do it. Hence there is no reason for the player developers to add support for it.