Ace Film

Overview
Ace Film is an animation file format used on early RISC OS systems (file type D6A, AceFilm), allowing graphics created using Ace Computing's applications to be stored as a series of frames in a file, to be replayed layer using the Projector application. Applications used to generate Ace Film files included Tween, Mogul and Euclid.

Format details
All lengths and offsets are in bytes. Words are 4 bytes.

0x0:   File length (4 bytes) 0x4:   Title (12 bytes, ASCII, low bytes ignored, can contain spaces) 0x10:  Offset into the file of data (data_offset) 0x14: 0x18: 0x1c:  Number of colours?

Each frame is described by a data length followed by the data itself, then followed by the data length again, presumably to make it easy to traverse the file in both directions:

data_offset:   length of data (including this word) (data_length) ...   data_offset + data_length - 4: data_length

Sample files

 * There are some examples in the Arcade BBS Filebase (may be Spark-compressed)