2. Basic matters

2.1 Terminology

Table 2.1 shows the definitions of the terms used.

Table 2.1 Definition of terms

the term	meaning
MPEG buffer	Memory area managed by MPEG / Video LSI.
Frame buffer	Area where the decoded image data is stored. It consists of multiple frame banks. It consists of 4 banks for normal resolution and 1 bank for high-definition resolution.
Frame bank	The area where the image data for one picture of the MPEG video stream is expanded.
VBV buffer	Area used to decode an MPEG video stream. It is allocated in the MPEG buffer.
Display window	A rectangular area on the TV monitor where the MPEG video is output. The data of the frame buffer window is output.
Framebuffer window	A rectangular area set for the framebuffer. This area is the output target.
Bright spot	The smallest display unit on the display.
Pixel	A display unit consisting of 2x2 bright spots at normal resolution and 1x1 bright spots at high-definition resolution.
Image data	Decoded color data. 16 to the host area It is transferred as bit color data.
MPEG window	An object for controlling the display window and framebuffer window.
MPEG video handle	An object for controlling MPEG video.
MPEG still image handle	An object for controlling MPEG still images.
MPEG handle	A generic term for MPEG video handles and MPEG still image handles.
MPEG report	Data that represents the state of the MPEG system. For details, refer to the manual of the CD communication interface.

2.2 MPEG stream

(1) What is MPEG?

MPEG is an international standard for video compression, which compresses video to 1.5 Mbit / sec. Image data is compressed to about 1/50 and audio data is compressed to about 1/10, and can be recorded on a standard speed CD.

(2) Picture type

The following three types of pictures are composed from the video compression method.

Table 2.2 Picture types

Picture type	explanation
I picture (Intra-coded Picture)	An image that can be decrypted only from your own information. Although the compression efficiency is poor, random access is possible if this image is inserted at regular intervals.
P picture (Predictive-coded Picture)	An image that uses another already decoded picture (I, P) as the predicted image.
B picture (Bidirectionally) predictive-coded Picture)	An image that uses two pictures (I, P) before and after as a prediction image. The compression efficiency is the best.

Figure 2.1 Predictive relationship between pictures

(3) GOP

A GOP (Group Of Picture) is composed of one or more I pictures and zero or more non-I pictures. GOP is a basic editing unit and can be played independently.
In order to decode the B picture, the I picture or P picture that is the predicted image must be decoded first. Therefore, the order in which the pictures are input to the decoder and the actual display order are interchanged.

Figure 2.2 Order on CD-ROM and playback image order