一哥技术馆 关于android视频采集的问题，急求解

最近在有个项目是关于android的视频采集，要求是捕捉某个事件发生前后30秒的视频片段。以前从没有做过android或多媒体开发，很多概念和技术不是很清楚，在网上各论坛转了很久，大致有个思路（MediaRecorder类不知道能不能满足上面的要求），就是利用Camera的PreviewCallback接口，通过实现onPreviewFrame（byte[] data, Camera camera）来捕捉每一帧数据，然后将data保存到文件里，问题是直接保存的数据无法播放，网上有人提供过decodeYUV420SP方法来将默认的YUV格式转码为RGB格式，问题是无论转码前还是转码后我都不知道应该保存为什么文件，是不是直接保存为后缀名为".3gp"或".mp4"就可以了？
我一直是在模拟器上调试的，不知道是不是一定需要在真机上运行才行。
跪求各达人显显灵，谢啦!

以下是我的代码，请各位达人斧正

Java code

import java.io.File;
import java.io.RandomAccessFile;

import android.app.Activity;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.Window;
import android.view.WindowManager;

public class AndroidCamera extends Activity implements SurfaceHolder.Callback {
    
    private SurfaceView mSurfaceView = null;
    private SurfaceHolder mSurfaceHolder = null;
    private Camera mCamera = null;
    
    private boolean mPreviewRunning = false;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        getWindow().setFormat(PixelFormat.TRANSLUCENT);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
                
        setContentView(R.layout.main);
        
        mSurfaceView = (SurfaceView)findViewById(R.id.surface_camera);
        mSurfaceHolder = mSurfaceView.getHolder();
        mSurfaceHolder.addCallback(this);
        mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        if(mPreviewRunning) {
            mCamera.stopPreview();
        }
        
        Camera.Parameters p = mCamera.getParameters();
        
        p.setPreviewSize(width, height);
        mCamera.setPreviewCallback(new VideoData(width, height));
        mCamera.setParameters(p);
        
        try {
            mCamera.setPreviewDisplay(holder);
        } catch(Exception e) {
            e.printStackTrace();
        }
        
        mCamera.startPreview();
        mPreviewRunning = true;
        
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mCamera = Camera.open();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        Log.v("AndroidCamera", "surfaceDestroyed");
        if(mCamera != null) {
            mCamera.setPreviewCallback(null);
            mCamera.stopPreview();
            mPreviewRunning =false;
            mCamera.release();
            mCamera = null;
        }
        
    }
}

class VideoData implements Camera.PreviewCallback {

    RandomAccessFile raf=null;
    byte[] h264Buff =null;
    
    public VideoData(int width, int height) {
        Log.v("androidCamera", "new VideoData");
        h264Buff = new byte[width * height *8];
        
        try {
            Log.v("androidCamera", "Create File: /sdcard/camera.dat start");
            File file = new File("/sdcard/camera.3gp");
            Log.v("androidCamera", "Create File: /sdcard/camera.dat end");
            raf = new RandomAccessFile(file, "rw");
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
    
    @Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        if(data == null) {
            return;
        }

        int previewWidth = camera.getParameters().getPreviewSize().width;
        int previewHeight = camera.getParameters().getPreviewSize().height;
        
        byte[] rgbBuffer = new byte[previewWidth * previewHeight * 3];
        
        decodeYUV420SP(rgbBuffer, data, previewWidth, previewHeight);
        
        try {
            raf.write(rgbBuffer, 0, data.length);
        } catch(Exception ex) {
            ex.printStackTrace();
        }
    }
    
    protected void finalize() {
        if (null != raf) {
            try {
                raf.close();
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
        
        try {
            super.finalize();
        } catch (Throwable e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    private void decodeYUV420SP(byte[] rgbBuf, byte[] yuv420sp, int width, int height) {    
        final int frameSize = width * height;    
        if (rgbBuf == null)    
            throw new NullPointerException("buffer 'rgbBuf' is null");    
        if (rgbBuf.length < frameSize * 3)    
            throw new IllegalArgumentException("buffer 'rgbBuf' size "   
                     + rgbBuf.length + " < minimum " + frameSize * 3);    
           
        if (yuv420sp == null)    
            throw new NullPointerException("buffer 'yuv420sp' is null");    
           
        if (yuv420sp.length < frameSize * 3 / 2)    
            throw new IllegalArgumentException("buffer 'yuv420sp' size " + yuv420sp.length    
                     + " < minimum " + frameSize * 3 / 2);    
                
        int i = 0, y = 0;    
        int uvp = 0, u = 0, v = 0;    
        int y1192 = 0, r = 0, g = 0, b = 0;    
            
        for (int j = 0, yp = 0; j < height; j++) {    
             uvp = frameSize + (j >> 1) * width;    
             u = 0;    
             v = 0;    
            for (i = 0; i < width; i++, yp++) {    
                 y = (0xff & ((int) yuv420sp[yp])) - 16;    
                if (y < 0) y = 0;    
                if ((i & 1) == 0) {    
                     v = (0xff & yuv420sp[uvp++]) - 128;    
                     u = (0xff & yuv420sp[uvp++]) - 128;    
                 }    
                    
                 y1192 = 1192 * y;    
                 r = (y1192 + 1634 * v);    
                 g = (y1192 - 833 * v - 400 * u);    
                 b = (y1192 + 2066 * u);    
                    
                if (r < 0) r = 0; else if (r > 262143) r = 262143;    
                if (g < 0) g = 0; else if (g > 262143) g = 262143;    
                if (b < 0) b = 0; else if (b > 262143) b = 262143;    
                    
                 rgbBuf[yp * 3] = (byte)(r >> 10);    
                 rgbBuf[yp * 3 + 1] = (byte)(g >> 10);    
                 rgbBuf[yp * 3 + 2] = (byte)(b >> 10);    
            }    
        }
    }
}