学习H264之前，最好阅读一下维基百科中有关H264的相关介绍，里面包含了其的发展历程、主要特点、参考文献、参考网站等。
研究H264的主要文件包括两份参考手册（一份是语法结构参考手册，一份是JM开发手册）和软件开发模型JM.x.y(Joint Model H264编解码参考开发模型)。
一、编码框架
1H264的编码框架主要如图1所示：
原来的英语解释是：
The Encoder includes two dataflow paths, a “forward” path (left to right, shown in blue) and a “reconstruction” path (right to left, shown in magenta). 1 Encoder (forward path) An input frame Fn 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 reconstructed (uF’n in the Figures; note that the unfiltered samples are used to form P). In Inter mode, P is formed by motion-compensated prediction from one or more reference frame(s). In the Figures, the reference frame is shown as the previous encoded frame F’n-1 ; however, the predicton for each macroblock may be formed from one or two past or future frames (in time order) that have already been encoded and reconstructed. The prediction P is subtracted from the current macroblock to produce a residual or difference macroblock Dn. This is transformed (using a block transform) and quantized to give X, a set of quantized transform coefficients. These coefficients are re-ordered and entropy encoded. The entropyencoded coefficients, together with side information required to decode the macroblock (such as the macroblock prediction mode, quantizer step size, motion vector information describing how the macroblock was motion-compensated, etc) form the compressed bitstream. This is passed to a Network Abstraction Layer (NAL) for transmission or storage. 2 Encoder (reconstruction path) The quantized macroblock coefficients X are decoded in order to reconstruct a frame for encoding of further macroblocks. The coefficients X are re-scaled (Q-1) and inverse transformed (T-1) to produce a difference macroblock Dn’. This is not identical to the original difference macroblock Dn ; the quantization process introduces losses and so Dn’ is a distorted version of Dn. The prediction macroblock P is added to Dn’ to create a reconstructed macroblock uF’n (a distorted 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’n.