经典好文推荐，通过阅读本文，您将收获以下知识点:
一、长曝光是什么？
二、MTK长曝光流程
三、MTK长曝光log分析
四、Sensor长曝光添加code参考
一、长曝光是什么？
长曝光是摄影术语，指通过慢速快门实现特殊效果的拍摄技术，常用于弱光环境或捕捉动态轨迹，如车灯轨迹、星轨等场景。
其核心原理是延长快门开启时间以增加进光量，需配合三脚架、快门线避免震动，并可通过调整光圈、感光度及使用ND滤镜控制曝光效果。
二、MTK长曝光流程
1.AE 收到上层长曝光设定(AE Mode OFF)
2.AE 设置Shutter 给Sensor
3.Vsync 间隔是否与长曝光设定一致
4.MTK MW抓到的buffer 是否ok
三、MTK 长曝光log分析
3.1. enable 长曝光 debug log 脚本
使用下面adb 命令，可以打开长曝光相关的log。
命令参考如：
adb wait-for-device
adb root
adb remount
::isp6s debug long exposure
adb shell setprop vendor.debug.aaa_sensor_mgr.enable 1
adb shell getprop vendor.debug.aaa_sensor_mgr.enable
adb shell pkill camera*
pause
3.2. log关键字
connect call|capture req#|frames count|MTK_SENSOR_EXPOSURE_TIME|setSensorExpTime|vsirq|AEEffectiveFrame|Hal3AFlowCtrl.*i8ExposureTime\(1000000000\)|setScenario
3.2.1 关键字注意事项
AEEffectiveFrame(0/1/2)
设定长曝光生效帧，0/2 都表示延迟2帧生效， 1表示延迟1帧生效
VSirq时间差 判断长曝光时间设定
VSirq时间差 判断长曝光时间设定。
3.3 长曝光1s log分析
3.3.1 长曝光的流程
1. 改变AE mode
AEmode 会被设置为0，比如（u4AeMode（1->0）,曝光结束后会恢复AE mode 1）
//i8ExposureTime(1000000000)： Hal3A 送1s曝光参数给AE
09-24 14:52:08.865741 10703 11482 D Hal3AFlowCtrl: m_rParam.u4AeMode(0), m_rParam.i8ExposureTime(1000000000), iValidateOpt(1)
2. 确认长曝光时间是否符合预期
1. HAL3a 是否正确解析到长曝光时间给AE。
log 举例如下：
//i8ExposureTime(1000000000)： Hal3A 送1s曝光参数给AE
09-24 14:52:08.865741 10703 11482 D Hal3AFlowCtrl: m_rParam.(0), m_rParam.i8ExposureTime(1000000000), iValidateOpt(1)
09-24 14:52:08.866019 10703 10862 D Hal3Av3 : [parseMeta] MTK_SENSOR_EXPOSURE_TIME(1000000000 -> 100000000)
2. 确认AE有没有把曝光时间送给camera 驱动。
log 举例如下：
//AE 通过aaa_sensor_mgr 下1s shutter 给Sensor
09-24 14:52:08.870095 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:1000000
3. 确认 vsirq 间隔有没有被拉长。
log 举例如下：
09-24 14:52:08.965443 10703 11482 D HwEventIRQ: [wait] VSIrq
//由于N+2 帧长曝光剩下，N+1 帧正常短曝光 100ms
09-24 14:52:08.970461 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:100000
//N+2 帧生效 跟第一个VSIrq 正好时间差别1s,如果时间不对，需要找vendor FAE 协助分析
09-24 14:52:09.965644 10703 11482 D HwEventIRQ: [wait] VSIrq
4. 长曝光生效帧确认
长曝光生效帧，0 和 2 都代表N+2 帧生效，1代表N+1 帧生效
log 举例如下：
//AEEffectiveFrame(0): 0/2： 都是 N+2 帧生效，1：是N+1 帧生效
09-24 14:52:05.634264 10703 11496 I aaa_common_custom.cpp: [cust_initSpecialLongExpOnOff] g_bIsSpecialLongExpOn(0) AEEffectiveFrame(0)
3.3.2 Android log分析
长曝光拍照时候，camera app 下发1s的曝光时间，经过层层传递给底层驱动，然后设置shutter 给寄存器，使能长曝光生效。
1s长曝光拍照Android log 举例：
1s长曝光拍照Android log信息如下：
09-24 14:52:05.323360 1324 11374 I CameraService: CameraService::connect call (PID 11038 "XXX", camera ID 2) and Camera API version 2
//Linetime 8500ns
09-24 14:52:05.600575 10703 11496 D ImgSensorDrv: [setScenario][setScenario]DevID = 2, m_LineTimeInus = 8500 Scenario id = 0, PixelClk = 280000000, PixelInLine = 3640, Framelength = 2548
//AEEffectiveFrame(0): 0/2： 都是 N+2 帧生效，1：是N+1 帧生效
09-24 14:52:05.634264 10703 11496 I aaa_common_custom.cpp: [cust_initSpecialLongExpOnOff] g_bIsSpecialLongExpOn(0) AEEffectiveFrame(0)
09-24 14:52:08.473743 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:100000
09-24 14:52:08.564662 10703 11482 D HwEventIRQ: [wait] VSIrq
09-24 14:52:08.572474 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:100000
09-24 14:52:08.664930 10703 11482 D HwEventIRQ: [wait] VSIrq
09-24 14:52:08.671269 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:100000
//capture req#:32 ：拍照帧号以及拍照决策走单帧
09-24 14:52:08.681183 10703 11197 I mtkcam-FeatureSettingPolicy: [evaluateCaptureSetting] (0xb400007536c4f420) capture req#:32
09-24 14:52:08.697639 10703 11197 D mtkcam-FeatureSettingPolicy: [evaluateCaptureSetting] capture request frames count(mainFrame:1, subFrames:0, preDummyFrames:0, postDummyFrames:0)
09-24 14:52:08.697684 10703 11197 D mtkcam-FeatureSettingPolicy: [dumpRequestOutputParams] request frames count(mainFrame:1, subFrames:0, preDummyFrames:0, postDummyFrames:0), needUnpackRaw(0)
09-24 14:52:08.764989 10703 11482 D HwEventIRQ: [wait] VSIrq
//解析到 1s shutter 的metadata
09-24 14:52:08.765996 10703 11197 D Hal3Av3 : [parseMeta] MTK_SENSOR_EXPOSURE_TIME(100000000 -> 1000000000)
09-24 14:52:08.768091 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:100000
09-24 14:52:08.865177 10703 11482 D HwEventIRQ: [wait] VSIrq
//i8ExposureTime(1000000000)： Hal3A 送1s曝光参数给AE
09-24 14:52:08.865741 10703 11482 D Hal3AFlowCtrl: m_rParam.u4AeMode(0), m_rParam.i8ExposureTime(1000000000), iValidateOpt(1)
09-24 14:52:08.866019 10703 10862 D Hal3Av3 : [parseMeta] MTK_SENSOR_EXPOSURE_TIME(1000000000 -> 100000000)
//AE 通过aaa_sensor_mgr 下1s shutter 给Sensor
09-24 14:52:08.870095 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:1000000
09-24 14:52:08.965443 10703 11482 D HwEventIRQ: [wait] VSIrq
//由于N+2 帧长曝光剩下，N+1 帧正常短曝光 100ms
09-24 14:52:08.970461 10703 11529 D aaa_sensor_mgr: [setSensorExpTime()] i4SensorDev:4 a_u4ExpTime:100000
//N+2 帧生效 跟第一个VSIrq 正好时间差别1s,如果时间不对，需要找vendor FAE 协助分析
09-24 14:52:09.965644 10703 11482 D HwEventIRQ: [wait] VSIrq
//退出长曝光...
09-24 14:52:05.758824 10703 11482 D HwEventIRQ: [wait] VSIrq
09-24 14:52:05.859109 10703 11482 D HwEventIRQ: [wait] VSIrq
09-24 14:52:05.959313 10703 11482 D HwEventIRQ: [wait] VSIrq
09-24 14:52:06.059459 10703 11482 D HwEventIRQ: [wait] VSIrq
3.3.3 长曝光 Kernel log分析
1. Camera sensor P1 SOF 长曝光生效帧。
Camera sensor P1 SOF 长曝光生效帧log 如下：
Camera sensor P1 SOF 长曝光生效帧
Camera sensor P1 SOF 长曝光1s kernel log 分析：
Camera sensor P1 SOF 长曝光生效帧
09-24 14:52:08.892884 0 0 I [T410752] kworker/u16: 5: [name:camera_isp&][ISP][ISP_BH_Workqueue] [1214.449352]
CAM_A P1_DON_32(0x00008800_0x04001f1f,0x00008800_0x04001f1f)dma done(0x1f385,0x0,0x0)int(0x3c24f,0x0,0x0)exe_us:32248 ,\,
CAM_A P1_SOF_33_33(0x00008800_0x04011f20,0x00008800_0x04011f20,0xe7200000,0xfa800000,0x20/0x1f),
int_us:100203,FBC:0x0001f385,cq:0xef27f000_0xef29f000 0x00000000_0x00000000 0x00000000_0x00000000,Don(0x00120074_0x00120074 0x00000000_0x00000000,0x00000000_0x00000000 0x00000000_0x00000000),DMA(0x1f385_0x1f385,0x0_0x0,0x0_0x0,0x16f700_0x16f700,0x0_0x0,0x0_0x0),CTL_EN(0x41effef_0x
09-24 14:52:08.895948 0 0 D [T411529] 3AEventThd: xxx_camera_sensor[write_shutter] [name:imgsensor_isp6s&] shutter =76923, framelength =7708
//进入长曝光模式
09-24 14:52:08.895976 0 0 D [T411529] 3AEventThd: xxx_camera_sensor[write_shutter] [name:imgsensor_isp6s&]enter long exposure mode shutter=76923
09-24 14:52:08.897748 0 0 D [T511529] 3AEventThd: xxx_camera_sensor[write_shutter] [name:imgsensor_isp6s&]after shutter =76923, framelength =65534
09-24 14:52:08.897897 0 0 D [T511529] 3AEventThd: xxx_camera_sensor[set_gain] [name:imgsensor_isp6s&]gain = 128, reg_gain = 0x800, max_gain:0x400
//int_us:100221: P1_SOF_33_33 -->P1_DON_33 帧间隔100ms
09-24 14:52:08.995120 0 0 I [T510752] kworker/u16: 5: [name:camera_isp&][ISP][ISP_BH_Workqueue] [1214.549568]
CAM_A P1_DON_33(0x00008800_0x04002020,0x00008800_0x04002020)dma done(0x1f385,0x0,0x0)int(0x3c24f,0x0,0x0)exe_us:32242 ,\,
CAM_A P1_SOF_34_34(0x00008800_0x04012021,0x00008800_0x04012021,0xe4a00000,0xfa400000,0x21/0x20),
int_us:100221,FBC:0x0001f385,cq:0xef23f000_0xef25f000 0x00000000_0x00000000 0x00000000_0x00000000,Don(0x00120074_0x00120074 0x00000000_0x00000000,0x00000000_0x00000000 0x00000000_0x00000000),DMA(0x1f385_0x1f385,0x0_0x0,0x0_0x0,0x16f700_0x16f700,0x0_0x0,0x0_0x0),CTL_EN(0x41effef_0x
09-24 14:52:08.996053 0 0 D [T611529] 3AEventThd: xxx_camera_sensor[write_shutter] [name:imgsensor_isp6s&] shutter =7692, framelength =65534
//退出长曝光模式
09-24 14:52:08.996063 0 0 D [T611529] 3AEventThd: xxx_camera_sensor[write_shutter] [name:imgsensor_isp6s&]exit long exposure mode shutter=7692
09-24 14:52:08.998142 0 0 D [T611529] 3AEventThd: xxx_camera_sensor[write_shutter] [name:imgsensor_isp6s&]after shutter =7692, framelength =7708
09-24 14:52:08.998213 0 0 D [T611529] 3AEventThd: xxx_camera_sensor[set_gain] [name:imgsensor_isp6s&]gain = 204, reg_gain = 0xcc0, max_gain:0x400
// int_us:1000196 : P1_SOF_34_34 --> P1_DON_34 曝光耗时1s
09-24 14:52:09.993351 0 0 I [T410000] kworker/u16: 1: [name:camera_isp&][ISP][ISP_BH_Workqueue] [1215.549770]
CAM_A P1_DON_34(0x00008800_0x04002121,0x00008800_0x04002121)dma done(0x1f385,0x0,0x0)int(0x3c24f,0x0,0x0)exe_us:32223 ,\,
CAM_A P1_SOF_35_35(0x00008800_0x04012122,0x00008800_0x04012122,0xe3e00000,0xfa000000,0x22/0x21),
int_us:1000196,FBC:0x0001f385,cq:0xef2bf000_0xef2de000 0x00000000_0x00000000 0x00000000_0x00000000,Don(0x00120074_0x00120074 0x00000000_0x00000000,0x00000000_0x00000000 0x00000000_0x00000000),DMA(0x1f385_0x1f385,0x0_0x0,0x0_0x0,0x16f700_0x16f700,0x0_0x0,0x0_0x0),CTL_EN(0x41effef_0
四、Sensor 长曝光添加code参考
进入退出长曝光寄存器，需要vendor FAE 提供，大致模板如下：
