I found some additional info about STi5518:
Overview
The STi5518 is a highly integrated single-chip decoder, designed for use in feature-rich mass-market set-top boxes. It integrates a high performance 32-bit CPU, a dedicated block for DVB/DirectTV transport demultiplexing and descrambling, modules for MPEG-2 video and audio decoding with 3D-surround and MP3 support, advanced display and graphics features, a digital video encoder, and all of the system peripherals required in a typical low-cost interactive receiver.
To cover the needs of DVD-capable set-top boxes, STi5518 integration options include a CSS decryption block, a Dolby Digital audio decoder and Macrovision copy protection.
An ATAPI interface support is built-in, supporting the glueless connection of standard Hard Disk Drives. In this way, the STi5518 is ideal for set-top boxes featuring trick modes such as live TV recording, pausing and time-shifting.
The STi5518 is backward compatible with the popular STi5500 set-top box decoder, allowing easy migration from the previous generation.
The high level of integration in a single PQFP-208 package makes the STi5518 ideally suited for low-cost, high volume set-top box applications
Features
Integrated 32-bit host CPU @ 81MHz
2 Kbytes of instruction cache, 2 Kbytes of data cache, and 4Kbytes of SRAM configurable as data cache.
Audio decoder
5.1 channel Dolby