Asset Bundle Internal Structure

An AssetBundle is essentially a set of objects grouped together into a serialized file. It is deployed as a data file which has a slightly different structure depending on whether it is a normal bundle or a scene bundle.

Normal AssetBundle structure.

Streamed scene AssetBundle structure.

Both types are archived and compressed in a same way.

AssetBundle compression

The ArchiveFileSystem container has the following structure:

The Compressed blocks shown above might have chunk-based compression or stream-based compression. Chunk-based compression (LZ4) means that the original data is split to chunks (subblocks) of equal size and that chunks are compressed independently. You should use this if you want realtime decompression - random read overhead is small. Stream-based compression (LZMA) uses the same dictionary when processing the whole block, it provides the highest possible compression ratio but supports only sequential reads.