Currently discussed and sample here: https://ffmpeg.org/trac/ffmpeg/ticket/1060 Copy-and-pasted description: It is a format based on PNG and partial re-encoding, as you can see when you look at it with e.g. http://sourceforge.net/projects/extractor-gtk/ Possibly contains some other encoding types, too. All container structures seem to be little-endian. Each "frame" contains a 4 byte size at offset 8. For the PNG encoded ones, offsets 16 - 24 seem to contain 4 16 bit values that indicate the offset and size of the image the PNG updates. After that seems to follow yet another size field containing the remaining bytes. Start of the following packet is always aligned to 16 bytes. There seems to be some kind of index at 0x190. This and the data start seems to be referenced in the header, at bytes 24 and 28.