android - 如何在Android中以每秒至少15帧的速度从Camera对象获取原始预览数据？

Question

我需要至少每秒 15 帧从 Camera 对象获取原始预览数据，但我只能在 110 毫秒内获得一帧，这意味着我每秒只能获得 9 帧。我在下面简要介绍了我的代码。

Camera mCamera = Camera.open();
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewFrameRate(30);
parameters.setPreviewFpsRange(15000,30000);
mCamera.setParameters(parameters);
mCamera.addCallbackBuffer(new byte[dataBufferSize]);
//dataBufferSize stands for the byte size for a picture frame
mCamera.addCallbackBuffer(new byte[dataBufferSize]);
mCamera.addCallbackBuffer(new byte[dataBufferSize]);
mCamera.setPreviewDisplay(videoCaptureViewHolder);
//videoCaptureViewHolder is a SurfaceHolder object
mCamera.setPreviewCallbackWithBuffer(new Camera.PreviewCallback() {
  private long timestamp=0;
  public synchronized void onPreviewFrame(byte[] data, Camera camera) {
    Log.v("CameraTest","Time Gap = "+(System.currentTimeMillis()-timestamp));
    timestamp=System.currentTimeMillis();
    //do picture data process
    camera.addCallbackBuffer(data);
    return;
  }
}
mCamera.startPreview();

在上面的简要代码中，dataBufferSize 和 videoCaptureViewHolder 是在其他语句中定义和计算或赋值的。

我运行我的代码，我可以在屏幕上看到预览，并得到以下日志:

...
V/CameraTest( 5396): Time Gap = 105
V/CameraTest( 5396): Time Gap = 112
V/CameraTest( 5396): Time Gap = 113
V/CameraTest( 5396): Time Gap = 115
V/CameraTest( 5396): Time Gap = 116
V/CameraTest( 5396): Time Gap = 113
V/CameraTest( 5396): Time Gap = 115
...

这意味着 onPreviewFrame(byte[] data, Camera camera) 每 110 毫秒调用一次，因此我每秒可以得到不超过 9 帧。而且无论我通过问题 setPreviewFrameRate() 设置什么预览帧率，以及我通过问题 setPreviewFpsRange() 设置什么预览 Fps 范围，日志都是一样的。

有人能帮我解决这个问题吗？我需要每秒至少 15 帧从 Camera 对象获取原始预览数据。提前谢谢你。

我把我的整个代码放在下面。

CameraTest.java

package test.cameratest;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import android.app.Activity;
import android.graphics.ImageFormat;
import android.hardware.Camera;
import android.hardware.Camera.ErrorCallback;
import android.hardware.Camera.Parameters;
import android.hardware.Camera.Size;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;

public class CameraTestActivity extends Activity {
    SurfaceView mVideoCaptureView;
    Camera mCamera;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mVideoCaptureView = (SurfaceView) findViewById(R.id.video_capture_surface);
        SurfaceHolder videoCaptureViewHolder = mVideoCaptureView.getHolder();
        videoCaptureViewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        videoCaptureViewHolder.addCallback(new Callback() {
            public void surfaceDestroyed(SurfaceHolder holder) {
            }

            public void surfaceCreated(SurfaceHolder holder) {
                startVideo();
            }

            public void surfaceChanged(SurfaceHolder holder, int format,
                    int width, int height) {
            }
        });
    }
    private void startVideo() {
        SurfaceHolder videoCaptureViewHolder = null;
        try {
            mCamera = Camera.open();
        } catch (RuntimeException e) {
            Log.e("CameraTest", "Camera Open filed");
            return;
        }
        mCamera.setErrorCallback(new ErrorCallback() {
            public void onError(int error, Camera camera) {
            }
        }); 
        Camera.Parameters parameters = mCamera.getParameters();
        parameters.setPreviewFrameRate(30);
        parameters.setPreviewFpsRange(15000,30000);
        List<int[]> supportedPreviewFps=parameters.getSupportedPreviewFpsRange();
        Iterator<int[]> supportedPreviewFpsIterator=supportedPreviewFps.iterator();
        while(supportedPreviewFpsIterator.hasNext()){
            int[] tmpRate=supportedPreviewFpsIterator.next();
            StringBuffer sb=new StringBuffer();
            sb.append("supportedPreviewRate: ");
            for(int i=tmpRate.length,j=0;j<i;j++){
                sb.append(tmpRate[j]+", ");
            }
            Log.v("CameraTest",sb.toString());
        }

        List<Size> supportedPreviewSizes=parameters.getSupportedPreviewSizes();
        Iterator<Size> supportedPreviewSizesIterator=supportedPreviewSizes.iterator();
        while(supportedPreviewSizesIterator.hasNext()){
            Size tmpSize=supportedPreviewSizesIterator.next();
            Log.v("CameraTest","supportedPreviewSize.width = "+tmpSize.width+"supportedPreviewSize.height = "+tmpSize.height);
        }

        mCamera.setParameters(parameters);
        if (null != mVideoCaptureView)
            videoCaptureViewHolder = mVideoCaptureView.getHolder();
        try {
            mCamera.setPreviewDisplay(videoCaptureViewHolder);
        } catch (Throwable t) {
        }
        Log.v("CameraTest","Camera PreviewFrameRate = "+mCamera.getParameters().getPreviewFrameRate());
        Size previewSize=mCamera.getParameters().getPreviewSize();
        int dataBufferSize=(int)(previewSize.height*previewSize.width*
                               (ImageFormat.getBitsPerPixel(mCamera.getParameters().getPreviewFormat())/8.0));
        mCamera.addCallbackBuffer(new byte[dataBufferSize]);
        mCamera.addCallbackBuffer(new byte[dataBufferSize]);
        mCamera.addCallbackBuffer(new byte[dataBufferSize]);
        mCamera.setPreviewCallbackWithBuffer(new Camera.PreviewCallback() {
            private long timestamp=0;
            public synchronized void onPreviewFrame(byte[] data, Camera camera) {
                Log.v("CameraTest","Time Gap = "+(System.currentTimeMillis()-timestamp));
                timestamp=System.currentTimeMillis();
                try{
                    camera.addCallbackBuffer(data);
                }catch (Exception e) {
                    Log.e("CameraTest", "addCallbackBuffer error");
                    return;
                }
                return;
            }
        });
        try {
            mCamera.startPreview();
        } catch (Throwable e) {
            mCamera.release();
            mCamera = null;
            return;
        }
    }
    private void stopVideo() {
        if(null==mCamera)
            return;
        try {
            mCamera.stopPreview();
            mCamera.setPreviewDisplay(null);
            mCamera.setPreviewCallbackWithBuffer(null);
            mCamera.release();
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }
        mCamera = null;
    }
    public void finish(){
        stopVideo();
        super.finish();
    };
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="test.cameratest"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="9" android:targetSdkVersion="10" android:maxSdkVersion="10"/>
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.VIBRATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
    <uses-permission android:name="android.permission.READ_CONTACTS"/>
    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS"/>
    <uses-permission android:name="android.permission.CALL_PHONE"/>
    <uses-permission android:name="android.permission.BOOT_COMPLETED"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_SETTINGS" />    
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".CameraTestActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

Answer 1

我很害怕，你不能。预览帧率设置是相机应用程序的提示(在单独的进程中运行) - 它可以自由接受或默默地忽略它。它也与预览帧检索无关

当您请求预览框架时，您只需说出您希望拥有它的外部应用程序。它的缓冲区在相机应用程序中分配，然后通过映射内存段传递给您的 Activity - 这需要时间。

您可能会在某些设备上获得所需的性能，但不一定在您正在使用的设备上。

如果您需要定义帧速率，则必须捕获视频，然后解析/解压缩生成的二进制流。