MPEG-2 Video Coding - Digital Video and Audio Broadcasting Technology - page 131

There is, however, a special type of DCT coding which results in better
image quality for the interlaced scanning method. This involves frame and
field coding of macroblocks (Fig.7.26.). In this method, macroblocks are
first recoded line by line before being subjected to DCT coding.

Macroblock

Slice

Video ES:
sequence
GOP
picture
slice
macroblock
block

Block

Frame

Fig. 7.28. Block, macroblock, slice and frame

Quantizer matrix
extension

Quantizer
scale factor

GOP Picture Slice Macroblock Macroblock Sequence

Pointer to
1st frame
of PES
packet

Picture header
Slice header

Sequence
header

GOP header

PES
header

Packetized Elementary Stream

Length indicator

DTS
PTS

PES
header

Transport stream

4 byte
TS header

184 byte
payload

Payload unit
start indicator = 1

Fig. 7.29. Structure of MPEG-2 video elementary stream