1. 1. Overview

This document summarizes the functions related to the MPEG part of the CD block and the external specifications related to the MPEG part of the CD communication interface.
The CD communication interface of the MPEG part is abbreviated as the MPEG communication interface.

1.1 System configuration

Figure 1.1 shows the MPEG-related system configuration.

Figure 1.1 MPEG-related system configuration

┌──────────────────────────────────────────┬─┐
│ ┌────────────────────────────────────────┐ │ │
│ │ Host side program (MPEG library, application, etc.) │ │ │
│ └────────────────────────────────────────┘ │ Ho │
│ │ │ ↑ │ │
│ │ CD communication function │ MPEG communication function │ │
│ ↓ ↓ │ │ │ │
│ ┌─────────────────────┐┌───┴───────┐│
│ │ CD communication interface │ │ (data transfer module such as DMA) │ │ │
│ └─────────────────────┘└───┬───────┘││
└─────────────────────────────┼────────────┴─┘
│ │ │
CD block │ │ │ │　
Communication with │ CD command │ MPEG command │ Extract data ↓ ↓ │　
┌─────────────────────────────┼────────────┬─┐
│ ┌────┴───┐ │ │ │
│ │ MPEG register │ │ C │
│ └────┬───┘ │ D │
│ CD part function MPEG part function │ │ │
│ ┌──────┐ ┌────────┐ │ Video │ B │
│ │ CD buffer ├───── → │ MPEG device ├───── ┤ Data │ │
│ └──────┘ MPEG └────┬───┘ │ │ │ │
│ Stream │ Audio data │ │ │ │
└───────────────────┼─────────┼────────────┴─┘
↓ ↓ ┌─────┐
┌────┐ ┌────┐ │ │ │
│ SCSP │ │ VDP2 ├─ → │ TV monitor │
└────┘ └────┘ │ │ │
└─────┘
To play MPEG and actually output video and audio, VDP2 and SCSP settings are required separately.
For the setting method, refer to the VDP2 and SCSP manuals.

In the CD part and the MPEG part, the CDC function and the CD block command are abbreviated as follows.

• CD communication function: CD communication interface function of the CD part
• CD command: CD block command for the CD part
• MPEG communication function: CD communication interface function of MPEG part
• MPEG command: CD block command for MPEG part

1.2 Features and features

The following (1) is the function of the CD communication interface, and (2) to (8) are the functions of the CD block.

(1) Communication function with the MPEG part of the CD block

1. A group of C language interface functions that communicate with the host for the MPEG part.
2. Issue a command to the MPEG part and receive a response.
3. It corresponds almost one-to-one with the MPEG command.

(2) MPEG video playback function

Decodes the MPEG stream (video / audio) stored in the buffer partition and plays the video. Video and audio streams are stored in separate buffer compartments.
The function of the CD part is used to read and store the stream in the buffer partition.

(3) Output destination switching function

The decoded image data can be output by the following method.

1. Output directly to the TV monitor through VDP2. (16 million colors)
2. Transfer to the host area and output using VDP. (32000 colors)

(4) Stream switching function

Two streams are stored in different buffer partitions, and playback is smoothly switched from one to the other at a fixed timing.

(5) Display screen control function

1. Window function You can set the display range of the decoded video as a window and further enlarge or reduce it.

2. Video effects You can apply video effects such as "mosaic", "blurring", and "luminescence key" to the decoded video.

(6) Still image playback function

A still image is reproduced by sequentially decoding an MPEG stream composed of all I pictures. (Equivalent to JPEG)

(7) MPEG frame buffer function

The decoded image data in the MPEG frame buffer can be read into the buffer partition, and conversely, the image data in the buffer partition can be written to the MPEG frame buffer.

(8) MPEG sector buffer function

The MPEG decoder can be stopped and the MPEG buffer can be used as an MPEG sector buffer for data storage. The MPEG sector buffer reads and writes sector by sector to and from the buffer partition.
(2048 bytes per sector, 256 sectors in total)