[x264/x265] Adaptive Quantization 使用指南与源码分析【待完善】

码率控制系列

• 码率控制之ABR
  码率控制之ABR 使用指南与分析
• 码率控制之MBTree
  宏块树 mbtree 使用指南与源码分析
  x264源码解析：码率控制之mbtree — — – x264_macroblock_tree
  x264源码解析：lookahead之frametype — x264_slicetype_path (Viterbi算法)
  x264源码解析：lookahead之md/mv — — x264_slicetype_frame_cost
  x264源码解析：lookahead之cost计算基础 x264_slicetype_mb_cost等
  x264源码解析：码率控制之mbtree — — – propagate 计算流程
  x264源码解析：码率控制之mbtree — — – qp调整
• 码率控制之AQ
  [x264/x265] Adaptive Quantization 使用指南与源码分析【本文】
  x264源码解析：码率控制之adaptive quantization
  x265源码解析：码率控制之adaptive quantization【待补充】
• 码率控制之VBV
  x264源码解析：码率控制之VBV 帧级
  x264源码解析：码率控制之VBV 宏块级

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自适应量化（Adaptive Quantization）or（Variance Adaptive Quantizati），由x264中引入。

WHY

It is based on the notion that the HVS is more sensitive to distortion in a relatively homogenous area than in an area with high contrast. The technique offers significant subjective improvement in parts with a distinct texture but low variance in the pixel values.

WHAT

• x264

--aq-mode      AQ method [1]
                        - 0: Disabled
                        - 1: Variance AQ (complexity mask)
                        - 2: Auto-variance AQ
                        - 3: Auto-variance AQ with bias to dark 

--aq-strength    Reduces blocking and blurring in flat and textured areas. [1.0]

说明：
1:each frame
2:across video
3:2+bias dark scene

strength值越大，作用越强，0不调整。
0.5: grain tune
0.6: animation tune
1.0: film tune
1.2: stillimage tune

• x265

--aq-mode <integer>           Mode for Adaptive Quantization - 0:none 1:uniform AQ 2:auto variance 3:auto variance with bias to dark scenes. Default 1
--aq-strength          Reduces blocking and blurring in flat and textured areas (0 to 3.0). Default 1.00

HOW

264

x264源码解析：码率控制之adaptive quantization

265

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