使用 AsyncTask 的 Android ICS 和 MJPEG
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【中文标题】使用 AsyncTask 的 Android ICS 和 MJPEG【英文标题】：Android ICS and MJPEG using AsyncTask 【发布时间】：2012-05-19 23:28:37 【问题描述】：我修改了 android and MJPEG 中的 MJPEG 查看器代码以使用 AsyncTask 工作（因此适用于 Ice Cream Sandwich (ICS)，4.0.4），这是我的代码。
如果有人对如何优化、清理或对代码进行更适当的处理有任何建议，请告诉我。感谢您帮助解决两个问题：
如果您有设备在流中，则锁定屏幕 并解锁屏幕它不会继续播放，直到您 杀死并恢复应用程序或旋转屏幕。我所有尝试使用 OnResume() 做某事或其他事情都会导致应用崩溃。
特别是我想恢复 AsyncTask MjpegInputStream.java 但无法让它工作。
MjpegActivity.java：
package com.demo.mjpeg;
import java.io.IOException;
import java.net.URI;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import com.demo.mjpeg.MjpegView.MjpegInputStream;
import com.demo.mjpeg.MjpegView.MjpegView;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Toast;
public class MjpegActivity extends Activity
private static final String TAG = "MjpegActivity";
private MjpegView mv;
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
//sample public cam
String URL = "http://trackfield.webcam.oregonstate.edu/axis-cgi/mjpg/video.cgi?resolution=800x600&%3bdummy=1333689998337";
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
mv = new MjpegView(this);
setContentView(mv);
new DoRead().execute(URL);
public void onPause()
super.onPause();
mv.stopPlayback();
public class DoRead extends AsyncTask<String, Void, MjpegInputStream>
protected MjpegInputStream doInBackground(String... url)
//TODO: if camera has authentication deal with it and don't just not work
HttpResponse res = null;
DefaultHttpClient httpclient = new DefaultHttpClient();
Log.d(TAG, "1. Sending http request");
try
res = httpclient.execute(new HttpGet(URI.create(url[0])));
Log.d(TAG, "2. Request finished, status = " + res.getStatusLine().getStatusCode());
if(res.getStatusLine().getStatusCode()==401)
//You must turn off camera User Access Control before this will work
return null;
return new MjpegInputStream(res.getEntity().getContent());
catch (ClientProtocolException e)
e.printStackTrace();
Log.d(TAG, "Request failed-ClientProtocolException", e);
//Error connecting to camera
catch (IOException e)
e.printStackTrace();
Log.d(TAG, "Request failed-IOException", e);
//Error connecting to camera
return null;
protected void onPostExecute(MjpegInputStream result)
mv.setSource(result);
mv.setDisplayMode(MjpegView.SIZE_BEST_FIT);
mv.showFps(true);
MjpegInputStream.java:
package com.demo.mjpeg.MjpegView;
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
public class MjpegInputStream extends DataInputStream
private static final String TAG = "MjpegInputStream";
private final byte[] SOI_MARKER = (byte) 0xFF, (byte) 0xD8 ;
private final byte[] EOF_MARKER = (byte) 0xFF, (byte) 0xD9 ;
private final String CONTENT_LENGTH = "Content-Length";
private final static int HEADER_MAX_LENGTH = 100;
private final static int FRAME_MAX_LENGTH = 40000 + HEADER_MAX_LENGTH;
private int mContentLength = -1;
public MjpegInputStream(InputStream in)
super(new BufferedInputStream(in, FRAME_MAX_LENGTH));
private int getEndOfSeqeunce(DataInputStream in, byte[] sequence) throws IOException
int seqIndex = 0;
byte c;
for(int i=0; i < FRAME_MAX_LENGTH; i++)
c = (byte) in.readUnsignedByte();
if(c == sequence[seqIndex])
seqIndex++;
if(seqIndex == sequence.length)
return i + 1;
else
seqIndex = 0;
return -1;
private int getStartOfSequence(DataInputStream in, byte[] sequence) throws IOException
int end = getEndOfSeqeunce(in, sequence);
return (end < 0) ? (-1) : (end - sequence.length);
private int parseContentLength(byte[] headerBytes) throws IOException, NumberFormatException
ByteArrayInputStream headerIn = new ByteArrayInputStream(headerBytes);
Properties props = new Properties();
props.load(headerIn);
return Integer.parseInt(props.getProperty(CONTENT_LENGTH));
public Bitmap readMjpegFrame() throws IOException
mark(FRAME_MAX_LENGTH);
int headerLen = getStartOfSequence(this, SOI_MARKER);
reset();
byte[] header = new byte[headerLen];
readFully(header);
try
mContentLength = parseContentLength(header);
catch (NumberFormatException nfe)
nfe.getStackTrace();
Log.d(TAG, "catch NumberFormatException hit", nfe);
mContentLength = getEndOfSeqeunce(this, EOF_MARKER);
reset();
byte[] frameData = new byte[mContentLength];
skipBytes(headerLen);
readFully(frameData);
return BitmapFactory.decodeStream(new ByteArrayInputStream(frameData));
MjpegView.java:
package com.demo.mjpeg.MjpegView;
import java.io.IOException;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.Typeface;
import android.util.AttributeSet;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MjpegView extends SurfaceView implements SurfaceHolder.Callback
private static final String TAG = "MjpegView";
public final static int POSITION_UPPER_LEFT = 9;
public final static int POSITION_UPPER_RIGHT = 3;
public final static int POSITION_LOWER_LEFT = 12;
public final static int POSITION_LOWER_RIGHT = 6;
public final static int SIZE_STANDARD = 1;
public final static int SIZE_BEST_FIT = 4;
public final static int SIZE_FULLSCREEN = 8;
private MjpegViewThread thread;
private MjpegInputStream mIn = null;
private boolean showFps = false;
private boolean mRun = false;
private boolean surfaceDone = false;
private Paint overlayPaint;
private int overlayTextColor;
private int overlayBackgroundColor;
private int ovlPos;
private int dispWidth;
private int dispHeight;
private int displayMode;
public class MjpegViewThread extends Thread
private SurfaceHolder mSurfaceHolder;
private int frameCounter = 0;
private long start;
private Bitmap ovl;
public MjpegViewThread(SurfaceHolder surfaceHolder, Context context)
mSurfaceHolder = surfaceHolder;
private Rect destRect(int bmw, int bmh)
int tempx;
int tempy;
if (displayMode == MjpegView.SIZE_STANDARD)
tempx = (dispWidth / 2) - (bmw / 2);
tempy = (dispHeight / 2) - (bmh / 2);
return new Rect(tempx, tempy, bmw + tempx, bmh + tempy);
if (displayMode == MjpegView.SIZE_BEST_FIT)
float bmasp = (float) bmw / (float) bmh;
bmw = dispWidth;
bmh = (int) (dispWidth / bmasp);
if (bmh > dispHeight)
bmh = dispHeight;
bmw = (int) (dispHeight * bmasp);
tempx = (dispWidth / 2) - (bmw / 2);
tempy = (dispHeight / 2) - (bmh / 2);
return new Rect(tempx, tempy, bmw + tempx, bmh + tempy);
if (displayMode == MjpegView.SIZE_FULLSCREEN)
return new Rect(0, 0, dispWidth, dispHeight);
return null;
public void setSurfaceSize(int width, int height)
synchronized(mSurfaceHolder)
dispWidth = width;
dispHeight = height;
private Bitmap makeFpsOverlay(Paint p, String text)
Rect b = new Rect();
p.getTextBounds(text, 0, text.length(), b);
int bwidth = b.width()+2;
int bheight = b.height()+2;
Bitmap bm = Bitmap.createBitmap(bwidth, bheight, Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(bm);
p.setColor(overlayBackgroundColor);
c.drawRect(0, 0, bwidth, bheight, p);
p.setColor(overlayTextColor);
c.drawText(text, -b.left+1, (bheight/2)-((p.ascent()+p.descent())/2)+1, p);
return bm;
public void run()
start = System.currentTimeMillis();
PorterDuffXfermode mode = new PorterDuffXfermode(PorterDuff.Mode.DST_OVER);
Bitmap bm;
int width;
int height;
Rect destRect;
Canvas c = null;
Paint p = new Paint();
String fps;
while (mRun)
if(surfaceDone)
try
c = mSurfaceHolder.lockCanvas();
synchronized (mSurfaceHolder)
try
bm = mIn.readMjpegFrame();
destRect = destRect(bm.getWidth(),bm.getHeight());
c.drawColor(Color.BLACK);
c.drawBitmap(bm, null, destRect, p);
if(showFps)
p.setXfermode(mode);
if(ovl != null)
height = ((ovlPos & 1) == 1) ? destRect.top : destRect.bottom-ovl.getHeight();
width = ((ovlPos & 8) == 8) ? destRect.left : destRect.right -ovl.getWidth();
c.drawBitmap(ovl, width, height, null);
p.setXfermode(null);
frameCounter++;
if((System.currentTimeMillis() - start) >= 1000)
fps = String.valueOf(frameCounter)+" fps";
frameCounter = 0;
start = System.currentTimeMillis();
ovl = makeFpsOverlay(overlayPaint, fps);
catch (IOException e)
e.getStackTrace();
Log.d(TAG, "catch IOException hit in run", e);
finally
if (c != null)
mSurfaceHolder.unlockCanvasAndPost(c);
private void init(Context context)
SurfaceHolder holder = getHolder();
holder.addCallback(this);
thread = new MjpegViewThread(holder, context);
setFocusable(true);
overlayPaint = new Paint();
overlayPaint.setTextAlign(Paint.Align.LEFT);
overlayPaint.setTextSize(12);
overlayPaint.setTypeface(Typeface.DEFAULT);
overlayTextColor = Color.WHITE;
overlayBackgroundColor = Color.BLACK;
ovlPos = MjpegView.POSITION_LOWER_RIGHT;
displayMode = MjpegView.SIZE_STANDARD;
dispWidth = getWidth();
dispHeight = getHeight();
public void startPlayback()
if(mIn != null)
mRun = true;
thread.start();
public void stopPlayback()
mRun = false;
boolean retry = true;
while(retry)
try
thread.join();
retry = false;
catch (InterruptedException e)
e.getStackTrace();
Log.d(TAG, "catch IOException hit in stopPlayback", e);
public MjpegView(Context context, AttributeSet attrs)
super(context, attrs); init(context);
public void surfaceChanged(SurfaceHolder holder, int f, int w, int h)
thread.setSurfaceSize(w, h);
public void surfaceDestroyed(SurfaceHolder holder)
surfaceDone = false;
stopPlayback();
public MjpegView(Context context)
super(context);
init(context);
public void surfaceCreated(SurfaceHolder holder)
surfaceDone = true;
public void showFps(boolean b)
showFps = b;
public void setSource(MjpegInputStream source)
mIn = source;
startPlayback();
public void setOverlayPaint(Paint p)
overlayPaint = p;
public void setOverlayTextColor(int c)
overlayTextColor = c;
public void setOverlayBackgroundColor(int c)
overlayBackgroundColor = c;
public void setOverlayPosition(int p)
ovlPos = p;
public void setDisplayMode(int s)
displayMode = s;
【问题讨论】：
我使用 libjpeg 创建了上述示例的更快版本。代码bitbucket.org/neuralassembly/simplemjpegview演示youtube.com/watch?v=fumv9p0_vWo 如果我们要使用多个摄像头，我们应该怎么做？所以我们会有几个不同的 URL，为了将 url 作为参数传递，我们应该把它传递到哪里？ @neuralassembly 我克隆了您的 bitbucket 存储库，但设法使用 MjpegInputStream 和 MjpegView 在片段中加载流 url。也可以使用 AsyncTaskLoader 来完成这项工作。奇怪的是，我可以在模拟器上成功编译并运行它，但是 mv 是全黑的！我有什么遗漏吗？ @bbodenmiller 上面的代码很棒！但我只是一直在循环播放视频...... @neuralassembly 试用了您的代码，效果很好！但我延迟了三秒钟，认为这可能是缓冲区问题我想知道是否有办法最小化这个问题? 【参考方案1】：干得好！ 对于你的 onResume() 问题，将下面的代码从 onCreate() 移到 onResume() 还不够吗？
//sample public cam
String URL = "http://trackfield.webcam.oregonstate.edu/axis-cgi/mjpg/video.cgi?resolution=800x600&%3bdummy=1333689998337";
mv = new MjpegView(this);
setContentView(mv);
new DoRead().execute(URL);
然后您只需重新创建 AsyncTask 的视图和新实例...我试过了，它对我有用...
【讨论】：
是的，我实际上是通过将一堆东西移动到 onResume() 来修复它。我在此处发布的代码中还发现了许多其他错误（基于更错误的代码），一旦我将它们全部修复，我将立即发布。首先想到的是在 try 块中它需要检查 c 是否为空。另一个原因是对中游的源没有错误处理。 你是对的......你的稳定性经验如何？我注意到在某些设备上，使用此代码可能会出现无响应（CPU @ 100%）...您是否遇到过此类问题？ 我只能使用模拟器和 Galaxy Nexus 进行测试，但它肯定不是世界上最稳定的代码。我想我可能在这方面略有改进，我会看看我今天可以修复和发布的内容。如果你的 mjpeg 流每秒给你很多帧，那么手机上的流将是一个相当糟糕和缓慢的流……我不得不把我的流调低一点。 10 fps 似乎还可以，我认为如果不是硬件加速，手机处理太多了。 感谢您提供此信息，我将使用不同的相机进行一些测试。很高兴看看您改进的代码，如果您打算在这里发布它，请告诉我！ 我会处理它，但可能需要几周时间，因为当时很多其他项目正处于紧要关头。【参考方案2】：如果您想使用用户名或密码访问您的网络摄像机，您可能希望将其添加到您的DefaultHttpClient，这对新手很有帮助，上面的代码将适用于需要身份验证的摄像机
CredentialsProvider provider = new BasicCredentialsProvider();
UsernamePasswordCredentials credentials = new UsernamePasswordCredentials("yourusername", "yourpassword");
provider.setCredentials(AuthScope.ANY, credentials);
DefaultHttpClient httpclient = new DefaultHttpClient();
httpclient.setCredentialsProvider(provider);
【讨论】：
【参考方案3】：感谢代码，非常有用
我想推荐一些优化技巧，这些技巧已经在我的代码中使用，整体性能可以轻松提升几倍。
在可能的情况下，我在帧读取期间删除了内存分配
private final static int HEADER_MAX_LENGTH = 100;
private final static int FRAME_MAX_LENGTH = 200000 + HEADER_MAX_LENGTH;
private final String CONTENT_LENGTH = "Content-Length:";
private final String CONTENT_END = "\r\n";
private final static byte[] gFrameData = new byte[FRAME_MAX_LENGTH];
private final static byte[] gHeader = new byte[HEADER_MAX_LENGTH];
BitmapFactory.Options bitmapOptions = new BitmapFactory.Options();
public Bitmap readMjpegFrame() throws IOException
mark(FRAME_MAX_LENGTH);
int headerLen = getStartOfSequence(SOI_MARKER);
if(headerLen < 0)
return false;
reset();
readFully(gHeader, 0, headerLen);
int contentLen;
try
contentLen = parseContentLength(gHeader, headerLen);
catch (NumberFormatException nfe)
nfe.getStackTrace();
Log.d(TAG, "catch NumberFormatException hit", nfe);
contentLen = getEndOfSequence(EOF_MARKER);
readFully(gFrameData, 0, contentLen);
Bitmap bm = BitmapFactory.decodeByteArray(gFrameData, 0, contentLen, bitmapOptions);
bitmapOptions.inBitmap = bm;
return bm;
优化parseContentLength，尽量去掉String操作
byte[] CONTENT_LENGTH_BYTES;
byte[] CONTENT_END_BYTES;
public MjpegInputStream(InputStream in)
super(new BufferedInputStream(in, FRAME_MAX_LENGTH));
bitmapOptions.inSampleSize = 1;
bitmapOptions.inPreferredConfig = Bitmap.Config.RGB_565;
bitmapOptions.inPreferQualityOverSpeed = false;
bitmapOptions.inPurgeable = true;
try
CONTENT_LENGTH_BYTES = CONTENT_LENGTH.getBytes("UTF-8");
CONTENT_END_BYTES = CONTENT_END.getBytes("UTF-8");
catch (UnsupportedEncodingException e)
e.printStackTrace();
private int findPattern(byte[] buffer, int bufferLen, byte[] pattern, int offset)
int seqIndex = 0;
for(int i=offset; i < bufferLen; ++i)
if(buffer[i] == pattern[seqIndex])
++seqIndex;
if(seqIndex == pattern.length)
return i + 1;
else
seqIndex = 0;
return -1;
private int parseContentLength(byte[] headerBytes, int length) throws IOException, NumberFormatException
int begin = findPattern(headerBytes, length, CONTENT_LENGTH_BYTES, 0);
int end = findPattern(headerBytes, length, CONTENT_END_BYTES, begin) - CONTENT_END_BYTES.length;
// converting string to int
int number = 0;
int radix = 1;
for(int i = end - 1; i >= begin; --i)
if(headerBytes[i] > 47 && headerBytes[i] < 58)
number += (headerBytes[i] - 48) * radix;
radix *= 10;
return number;
代码中可能有错误，因为我正在为***重写它，最初我使用2个线程，一个是读取帧，另一个是渲染。
我希望它对某人有所帮助。
【讨论】：
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