下面介紹錄像的相關流程——從上層應用到底層實現整個流程，其重點主要是底層的流程。

5.1 上層

對于上層來說，整個流程不難，具體的流程圖如下：

image.png

另外，在進入預覽之后可以進行如下操作：
1、拍照或點擊屏幕會走JpegPictureCallback的onPictureTaken方法
2、暫停pauseVideoRecording方法，再次點擊暫停會走resumeVideoRecording方法然后會繼續updateRecordingTime；
3、中間的按鈕會走onShutterButtonClick方法;
4、點擊閃光燈按鈕 onFlashButtonClicked-----> setFlashMode;

5.2 底層

錄像前面的過程主要是MediaRecorder，下面只分析在HAL層的處理流程。

5.2.1 HAL層

hardware/qcom/camera/QCamera2/HAL/QCamera2HWI.cpp

**int **QCamera2HardwareInterface::start_recording(**struct
 **camera_device *device)
 {
     ATRACE_CALL();
     **int **ret = NO_ERROR;
     QCamera2HardwareInterface *hw =
         **reinterpret_cast**<QCamera2HardwareInterface
 *>(device->priv);
     **if **(!hw) {
         ALOGE("NULL camera
 device");
         **return **BAD_VALUE;
     }
     CDBG_HIGH("[KPI Perf] %s: E
 PROFILE_START_RECORDING", __func__);
     hw->lockAPI();
     qcamera_api_result_t apiResult;
     ret = hw->processAPI(QCAMERA_SM_EVT_START_RECORDING,
 NULL);
     **if **(ret == NO_ERROR) {
        
 hw->waitAPIResult(QCAMERA_SM_EVT_START_RECORDING, &apiResult);
         ret = apiResult.status;
     }
     hw->unlockAPI();
     hw->m_bRecordStarted = **true**;
     CDBG_HIGH("[KPI Perf] %s:
 X", __func__);
     **return **ret;
 }

更改了狀態機的狀態。

**case **QCAMERA_SM_EVT_START_RECORDING:
     {
         rc =
 m_parent->startRecording();
         **if **(rc == NO_ERROR) {
             // move state to recording
 state
             m_state =
 QCAMERA_SM_STATE_RECORDING;
        
 }
         result.status = rc;
         result.request_api = evt;
         result.result_type =
 QCAMERA_API_RESULT_TYPE_DEF;
        
 m_parent->signalAPIResult(&result);
     }
     **break**;

返回到QCamera2HWI.cpp的startRecording方法。

**int **QCamera2HardwareInterface::startRecording()
 {
     int32_t rc = NO_ERROR;
     CDBG_HIGH("%s: E",
 __func__);
     **if **(mParameters.getRecordingHintValue()
 == **false**) {
         CDBG_HIGH("%s: start
 recording when hint is false, stop preview first", __func__);
         stopPreview();

         // Set recording hint to TRUE
        
 mParameters.updateRecordingHintValue(TRUE);
         rc = preparePreview();
         **if **(rc == NO_ERROR) {
             rc =
 startChannel(QCAMERA_CH_TYPE_PREVIEW);
         }
     }

     //link meta stream with video
 channel if low power mode is enabled.
     **if **(mParameters.isLowPowerEnabled())
 {
         // Find and try to link a
 metadata stream from preview channel
         QCameraChannel *pMetaChannel =
 NULL;
         QCameraStream *pMetaStream =
 NULL;
         QCameraChannel *pVideoChannel =
 m_channels[QCAMERA_CH_TYPE_VIDEO];

         **if **(m_channels[QCAMERA_CH_TYPE_PREVIEW]
 != NULL) {
             pMetaChannel =
 m_channels[QCAMERA_CH_TYPE_PREVIEW];
             uint32_t streamNum =
 pMetaChannel->getNumOfStreams();
             QCameraStream *pStream =
 NULL;
             **for **(uint32_t i = 0
 ; i < streamNum ; i++ ) {
                 pStream =
 pMetaChannel->getStreamByIndex(i);
                 **if **((NULL !=
 pStream) &&
                         (CAM_STREAM_TYPE_METADATA
 == pStream->getMyType())) {
                     pMetaStream =
 pStream;
                     **break**;
                 }
             }
         }

         **if **((NULL !=
 pMetaChannel) && (NULL != pMetaStream)) {
             rc =
 pVideoChannel->linkStream(pMetaChannel, pMetaStream);
             **if **(NO_ERROR != rc)
 {
                 CDBG_HIGH("%s :
 Metadata stream link failed %d", __func__, rc);
             }
         }
     }

     **if **(rc == NO_ERROR) {
         rc =
 startChannel(QCAMERA_CH_TYPE_VIDEO);
     }

 #ifdef HAS_MULTIMEDIA_HINTS
     **if **(rc == NO_ERROR) {
         **if **(m_pPowerModule) {
             **if **(m_pPowerModule->powerHint)
 {
                
 m_pPowerModule->powerHint(m_pPowerModule, POWER_HINT_VIDEO_ENCODE,
 (**void ***)"state=1");
             }
         }
     }
 #endif
     CDBG_HIGH("%s: X",
 __func__);
     **return **rc;
 }

之后就是添加channel，并且啟動，然后設置buff，和數據流，之后在mm-camera-stream中對數據流接收處理，然后保存成文件，逐層向上拋數據。在此不做分析。