H.264_mpeg-4part_10_paper.

www.vcodex.com H.264 / MPEG-4 Part 10 : Overview

© Iain E G Richardson 07/10/02 Page 1 of 1

H.264 / MPEG-4 Part 10 White Paper

1. Introduction

Group and the Video Coding Experts Group (MPEG and VCEG) are in the final stages of developing

a new standard that promises to significantly outperform MPEG4 and H.263, providing better

compression of video images together with a range of features supporting high-quality, low-bitrate

streaming video. The history of the new standard, “Advanced Video Coding” (AVC), goes back at

extra features to H.263 (resulting in Version 2 of the standard) and a “long-term” effort to develop a

new standard for low bitrate visual communications. The long-term effort led to the draft “H.26L”

2. H.264 CODEC

however, a compliant encoder and decoder are likely to include the functional elements shown in

Figure 2-1 and Figure 2-2. Whilst the functions shown in these Figures are likely to be necessary for

compliance, there is scope for considerable variation in the structure of the CODEC. The basic

functional elements (prediction, transform, quantization, entropy encoding) are little different from

previous standards (MPEG1, MPEG2, MPEG4, H.261, H.263); the important changes in H.264 occur

www.vcodex.com H.264 / MPEG-4 Part 10 : Overview

© Iain E G Richardson 07/10/02 Page 2 of 2

F'

n-1

(reference)

MC

Intra

P

X

D'

Intra

prediction

n-1

An input frame F

is presented for encoding. The frame is processed in units of a macroblock

(corresponding to 16x16 pixels in the original image). Each macroblock is encoded in intra or inter

mode. In either case, a prediction macroblock P is formed based on a reconstructed frame. In Intra

mode, P is formed from samples in the current frame n that have previously encoded, decoded and

quantized transform coefficients. These coefficients are re-ordered and entropy encoded. The entropy-

encoded coefficients, together with side information required to decode the macroblock (such as the

macroblock was motion-compensated, etc) form the compressed bitstream. This is passed to a

2.2 Encoder (reconstruction path)

www.vcodex.com H.264 / MPEG-4 Part 10 : Overview

© Iain E G Richardson 07/10/02 Page 3 of 3

version of the original macroblock). A filter is applied to reduce the effects of blocking distortion and

reconstructed reference frame is created from a series of macroblocks F’

2.3 Decoder

.

will not be identical, leading to an increasing error or “drift” between the encoder and decoder.

3. References