android camera系统3A模式及其状态转换（二）

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我是靠谱客的博主爱听歌天空，最近开发中收集的这篇文章主要介绍android camera系统3A模式及其状态转换（二），觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

5. AF state machines

State	Transformation cause	New state	Notes
mode = AF_MODE_OFF or AF_MODE_EDOF
INACTIVE			AF is disabled
mode = AF_MODE_AUTO or AF_MODE_MACRO
State	Transformation cause	New state	Notes
INACTIVE	AF_TRIGGER	ACTIVE_SCAN	Start AF sweep Lens now moving
ACTIVE_SCAN	AF sweep done	FOCUSED_LOCKED	If AF successful Lens now locked
ACTIVE_SCAN	AF sweep done	NOT_FOCUSED_LOCKED	If AF successful Lens now locked
ACTIVE_SCAN	AF_CANCEL	INACTIVE	Cancel/reset AF Lens now locked
FOCUSED_LOCKED	AF_CANCEL	INACTIVE	Cancel/reset AF
FOCUSED_LOCKED	AF_TRIGGER	ACTIVE_SCAN	Start new sweep Lens now moving
NOT_FOCUSED_LOCKED	AF_CANCEL	INACTIVE	Cancel/reset AF
NOT_FOCUSED_LOCKED	AF_TRIGGER	ACTIVE_SCAN	Start new sweep Lens now moving
All states	mode change	INACTIVE
mode = AF_MODE_CONTINUOUS_VIDEO
State	Transformation cause	New state	Notes
INACTIVE	HAL initiates new scan	PASSIVE_SCAN	Start AF sweep Lens now moving
INACTIVE	AF_TRIGGER	NOT_FOCUSED_LOCKED	AF state query Lens now locked
PASSIVE_SCAN	HAL completes current scan	PASSIVE_FOCUSED	End AF scan Lens now locked
PASSIVE_SCAN	AF_TRIGGER	FOCUSED_LOCKED	Immediate transformation if focus is good Lens now locked
PASSIVE_SCAN	AF_TRIGGER	NOT_FOCUSED_LOCKED	Immediate transformation if focus is bad Lens now locked
PASSIVE_SCAN	AF_CANCEL	INACTIVE	Reset lens position Lens now locked
PASSIVE_FOCUSED	HAL initiates new scan	PASSIVE_SCAN	Start AF scan Lens now moving
PASSIVE_FOCUSED	AF_TRIGGER	FOCUSED_LOCKED	Immediate transformation if focus is good Lens now locked
PASSIVE_FOCUSED	AF_TRIGGER	NOT_FOCUSED_LOCKED	Immediate transformation if focus is bad Lens now locked
FOCUSED_LOCKED	AF_TRIGGER	FOCUSED_LOCKED	No effect
FOCUSED_LOCKED	AF_CANCEL	INACTIVE	Restart AF scan
NOT_FOCUSED_LOCKED	AF_TRIGGER	NOT_FOCUSED_LOCKED	No effect
NOT_FOCUSED_LOCKED	AF_CANCEL	INACTIVE	Restart AF scan
mode = AF_MODE_CONTINUOUS_PICTURE
State	Transformation cause	New state	Notes
INACTIVE	HAL initiates new scan	PASSIVE_SCAN	Start AF scan Lens now moving
INACTIVE	AF_TRIGGER	NOT_FOCUSED_LOCKED	AF state query Lens now locked
PASSIVE_SCAN	HAL completes current scan	PASSIVE_FOCUSED	End AF scan Lens now locked
PASSIVE_SCAN	AF_TRIGGER	FOCUSED_LOCKED	Eventual transformation once focus good Lens now locked
PASSIVE_SCAN	AF_TRIGGER	NOT_FOCUSED_LOCKED	Eventual transformation if cannot focus Lens now locked
PASSIVE_SCAN	AF_CANCEL	INACTIVE	Reset lens position Lens now locked
PASSIVE_FOCUSED	HAL initiates new scan	PASSIVE_SCAN	Start AF scan Lens now moving
PASSIVE_FOCUSED	AF_TRIGGER	FOCUSED_LOCKED	Immediate transformation if focus is good Lens now locked
PASSIVE_FOCUSED	AF_TRIGGER	NOT_FOCUSED_LOCKED	Immediate transformation if focus is bad Lens now locked
FOCUSED_LOCKED	AF_TRIGGER	FOCUSED_LOCKED	No effect
FOCUSED_LOCKED	AF_CANCEL	INACTIVE	Restart AF scan
NOT_FOCUSED_LOCKED	AF_TRIGGER	NOT_FOCUSED_LOCKED	No effect
NOT_FOCUSED_LOCKED	AF_CANCEL	INACTIVE	Restart AF scan

6. AE and AWB state machines

AE和AWB的状态机基本上是完全相同的。AE有额外的FLASH_REQUIRED和PRECAPTURE状态。所以下面行中涉及这两个状态时，AWB状态机忽略之。

State	Transformation cause	New state	Notes
mode = AE_MODE_OFF / AWB mode not AUTO
INACTIVE			AE/AWB disabled
*mode = AE_MODE_ON_ / AWB_MODE_AUTO**
State	Transformation cause	New state	Notes
INACTIVE	HAL initiates AE/AWB scan	SEARCHING
INACTIVE	AE/AWB_LOCK on	LOCKED	Values locked
SEARCHING	HAL finishes AE/AWB scan	CONVERGED	Good values, not changing
SEARCHING	HAL finishes AE scan	FLASH_REQUIRED	Converged but too dark without flash
SEARCHING	AE/AWB_LOCK on	LOCKED	Values locked
CONVERGED	HAL initiates AE/AWB scan	SEARCHING	Values locked
CONVERGED	AE/AWB_LOCK on	LOCKED	Values locked
FLASH_REQUIRED	HAL initiates AE/AWB scan	SEARCHING	Values locked
FLASH_REQUIRED	AE/AWB_LOCK on	LOCKED	Values locked
LOCKED	AE/AWB_LOCK off	SEARCHING	Values not good after unlock
LOCKED	AE/AWB_LOCK off	CONVERGED	Values good after unlock
LOCKED	AE_LOCK off	FLASH_REQUIRED	Exposure good, but too dark
All AE states	PRECAPTURE_START	PRECAPTURE	Start precapture sequence
PRECAPTURE	Sequence done, AE_LOCK off	CONVERGED	Ready for high-quality capture
PRECAPTURE	Sequence done, AE_LOCK on	LOCKED	Ready for high-quality capture

7. Enabling manual control

在配置3A模块中所涉及的一些控制，允许application直接控制。

对于每个请求，HAL层负责3A控制的模块会检查3A控制字段的状态。如果有3A事例使能，这些事例可能会重置该事例相关的控制变量，重置的值会放置于此次捕获的结果元数据中。例如，如果在一个请求中自动曝光使能，HAL层会重置这个请求中的曝光值，增益和帧周期字段（和潜在的闪光灯字段，依赖于AE模式）。相关控制如下：

Control name	Unit	Notes
android.control.mode	enum: OFF, AUTO, USE_SCENE_MODE	High-level 3A control. When set to OFF, all 3A control by the HAL is disabled. The application must set the fields for capture parameters itself. When set to AUTO, the individual algorithm controls in android.control.* are in effect, such as android.control.afMode. When set to USE_SCENE_MODE, the individual controls in android.control.* are mostly disabled, and the HAL implements one of the scene mode settings (such as ACTION, SUNSET, or PARTY) as it wishes.
android.control.afMode	enum	OFF means manual control of lens focusing through android.lens.focusDistance.
android.control.aeMode	enum	OFF means manual control of exposure/gain/frame duration through android.sensor.exposureTime / .sensitivity / .frameDuration
android.control.awbMode	enum	OFF means manual control of white balance.