玩轉 Android MediaPlayer之視頻預加載(優化)

本文是在《玩轉 Android MediaPlayer之視頻預加載》基礎上做更進一步的優化，適應更多終端的MediaPlayer，不再嘮叨預加載的作用和基礎，有興趣的讀者請看上回。

MediaPlayer由廠家定製，不同終端的MediaPlayer略有差異，例如：有些MediaPlayer首次播放從頭buffer，有些MdiaPlayer首次播放會多次Request，Range到網絡媒體文件的頭部、中間和文件尾，再從指定位置buffer...本文所做的優化就是適應播放前多次Request的MediaPlayer。

決定預加載效果好壞由三因素決定：

網速
緩衝文件大小
視頻碼率

碼率低、網速快的情況沒必要使用預加載，碼率中等、網速一般的情況合適使用。另外，緩衝文件也不能設置太大：過大的緩衝區會刷爆MediaPlayer內置的緩衝區，影響正常播放；再者，讀取緩衝文件也耗時。

先看看本文程序的運行結果，以下是不使用預加載的運行LOG：

08-27 10:34:55.222: E//mnt/sdcard/ProxyBuffer/files(12949): --------共有0個緩存文件
08-27 10:34:55.327: E/MediaPlayer(12949): MediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:34:55.327: E/(12949): IMediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:34:55.367: E/MediaPlayer(12949): MediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:34:55.367: E/(12949): IMediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:35:01.152: E/MediaPlayer(12949): MediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:35:01.152: E/(12949): IMediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:35:01.402: E/MediaPlayer(12949): MediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:35:01.402: E/(12949): IMediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:35:02.382: E/testVideoPlayer(12949): 預加載開關:false,等待緩衝時間:8000,首次緩衝時間:7152

以下是使用預加載的運行LOG，內容有點多，這個MediaPlayer就是首次播放前多次Request：

08-27 10:40:02.627: E//mnt/sdcard/ProxyBuffer/files(13769): --------共有0個緩存文件
08-27 10:40:02.777: E/testVideoPlayer(13769): 預加載文件：/mnt/sdcard/ProxyBuffer/files/videorzx201208151345010952759.mp4
08-27 10:40:02.972: E/DownloadThread(13769): /mnt/sdcard/ProxyBuffer/files/videorzx201208151345010952759.mp4
08-27 10:40:10.782: E/MediaPlayer(13769): MediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:40:10.782: E/(13769): IMediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:40:10.787: E/HttpGetProxy(13769): ------------------------------------------------------------------
08-27 10:40:10.787: E/HttpGetProxy(13769): java.lang.NullPointerException
08-27 10:40:10.787: E/HttpGetProxy(13769): com.proxy.HttpGetProxy.startProxy 171line

08-27 10:40:10.787: E/HttpGetProxy(13769): com.proxy.HttpGetProxy.access$0 134line

08-27 10:40:10.787: E/HttpGetProxy(13769): com.proxy.HttpGetProxy$1.run 129line

08-27 10:40:10.787: E/HttpGetProxy(13769): ------------------------------------------------------------------
08-27 10:40:10.792: E/HttpParser(13769): GET /video/rzx/201208/15/1345010952759.mp4 HTTP/1.1

08-27 10:40:10.792: E/HttpParser(13769): Range: bytes=0-

08-27 10:40:10.792: E/HttpParser(13769): Host: video.cztv.com

08-27 10:40:10.792: E/HttpParser(13769): Accept: */*

08-27 10:40:10.792: E/HttpParser(13769): Pragma: no-cache

08-27 10:40:10.792: E/HttpParser(13769):

08-27 10:40:10.792: E/HttpParser(13769): _prebufferFilePath:/mnt/sdcard/ProxyBuffer/files/videorzx201208151345010952759.mp4
08-27 10:40:10.792: E/HttpParser(13769): ------->rangePosition:0
08-27 10:40:10.792: E/HttpGetProxy(13769): prebuffer size:999296
08-27 10:40:10.797: E/DownloadThread(13769): mTotalSize:8311866,mTargetSize:3145728
08-27 10:40:11.762: E/HttpGetProxy<---(13769): HTTP/1.1 206 Partial Content

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Date: Mon, 27 Aug 2012 02:33:24 GMT

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Server: Apache

08-27 10:40:11.762: E/HttpGetProxy<---(13769): X-Mod-H264-Streaming: version=2.2.7

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Last-Modified: Wed, 15 Aug 2012 06:24:38 GMT

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Accept-Ranges: bytes

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Cache-Control: max-age=315360000

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Expires: Thu, 25 Aug 2022 02:33:24 GMT

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Content-Type: video/mp4

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Powered-By-ChinaCache: HIT from 01006613Y4

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Content-Range: bytes 0-8311865/8311866

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Content-Length: 8311866

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Age: 407

08-27 10:40:11.762: E/HttpGetProxy<---(13769): Powered-By-ChinaCache: HIT from 01075913r4

08-27 10:40:11.762: E/HttpGetProxy<---(13769):

08-27 10:40:11.777: E/HttpGetProxy(13769): .........over..........
08-27 10:40:11.777: E/HttpGetProxy(13769): ------------------------------------------------------------------
08-27 10:40:11.782: E/HttpParser(13769): GET /video/rzx/201208/15/1345010952759.mp4 HTTP/1.1

08-27 10:40:11.782: E/HttpParser(13769): Range: bytes=101901-

08-27 10:40:11.782: E/HttpParser(13769): Host: video.cztv.com

08-27 10:40:11.782: E/HttpParser(13769): Accept: */*

08-27 10:40:11.782: E/HttpParser(13769): Pragma: no-cache

08-27 10:40:11.782: E/HttpParser(13769):

08-27 10:40:11.782: E/HttpParser(13769): _prebufferFilePath:/mnt/sdcard/ProxyBuffer/files/videorzx201208151345010952759.mp4
08-27 10:40:11.782: E/HttpParser(13769): ------->rangePosition:101901
08-27 10:40:11.782: E/HttpGetProxy(13769): prebuffer size:1000320
08-27 10:40:12.167: E/HttpGetProxy<---(13769): HTTP/1.1 206 Partial Content

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Date: Mon, 27 Aug 2012 02:33:24 GMT

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Server: Apache

08-27 10:40:12.167: E/HttpGetProxy<---(13769): X-Mod-H264-Streaming: version=2.2.7

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Last-Modified: Wed, 15 Aug 2012 06:24:38 GMT

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Accept-Ranges: bytes

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Cache-Control: max-age=315360000

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Expires: Thu, 25 Aug 2022 02:33:24 GMT

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Content-Type: video/mp4

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Powered-By-ChinaCache: HIT from 01006613Y4

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Content-Range: bytes 101901-8311865/8311866

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Content-Length: 8209965

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Age: 408

08-27 10:40:12.167: E/HttpGetProxy<---(13769): Powered-By-ChinaCache: HIT from 01075913r4

08-27 10:40:12.167: E/HttpGetProxy<---(13769):

08-27 10:40:12.172: E/HttpGetProxy(13769): >>>skip:101901
08-27 10:40:12.182: E/HttpGetProxy(13769): .........over..........
08-27 10:40:12.182: E/HttpGetProxy(13769): ------------------------------------------------------------------
08-27 10:40:12.187: E/HttpParser(13769): GET /video/rzx/201208/15/1345010952759.mp4 HTTP/1.1

08-27 10:40:12.187: E/HttpParser(13769): Range: bytes=74-

08-27 10:40:12.187: E/HttpParser(13769): Host: video.cztv.com

08-27 10:40:12.187: E/HttpParser(13769): Accept: */*

08-27 10:40:12.187: E/HttpParser(13769): Pragma: no-cache

08-27 10:40:12.187: E/HttpParser(13769):

08-27 10:40:12.187: E/HttpParser(13769): _prebufferFilePath:/mnt/sdcard/ProxyBuffer/files/videorzx201208151345010952759.mp4
08-27 10:40:12.187: E/HttpParser(13769): ------->rangePosition:74
08-27 10:40:12.187: E/HttpGetProxy(13769): prebuffer size:1000320
08-27 10:40:12.372: E/HttpGetProxy<---(13769): HTTP/1.1 206 Partial Content

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Date: Mon, 27 Aug 2012 02:33:24 GMT

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Server: Apache

08-27 10:40:12.372: E/HttpGetProxy<---(13769): X-Mod-H264-Streaming: version=2.2.7

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Last-Modified: Wed, 15 Aug 2012 06:24:38 GMT

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Accept-Ranges: bytes

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Cache-Control: max-age=315360000

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Expires: Thu, 25 Aug 2022 02:33:24 GMT

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Content-Type: video/mp4

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Powered-By-ChinaCache: HIT from 01006613Y4

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Content-Range: bytes 74-8311865/8311866

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Content-Length: 8311792

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Age: 408

08-27 10:40:12.372: E/HttpGetProxy<---(13769): Powered-By-ChinaCache: HIT from 01075913r4

08-27 10:40:12.372: E/HttpGetProxy<---(13769):

08-27 10:40:12.377: E/HttpGetProxy(13769): >>>skip:74
08-27 10:40:12.397: E/MediaPlayer(13769): MediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:40:12.397: E/(13769): IMediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:40:12.537: E/HttpGetProxy(13769): >>>讀取預加載耗時:164
08-27 10:40:12.537: E/HttpGetProxy(13769): >>>讀取完畢...下載:1000320,讀取:1000246
08-27 10:40:12.537: E/HttpGetProxy-pre->(13769): GET /video/rzx/201208/15/1345010952759.mp4 HTTP/1.1

08-27 10:40:12.537: E/HttpGetProxy-pre->(13769): Range: bytes=1000320-

08-27 10:40:12.537: E/HttpGetProxy-pre->(13769): Host: video.cztv.com

08-27 10:40:12.537: E/HttpGetProxy-pre->(13769): Accept: */*

08-27 10:40:12.537: E/HttpGetProxy-pre->(13769): Pragma: no-cache

08-27 10:40:12.537: E/HttpGetProxy-pre->(13769):

08-27 10:40:12.647: E/MediaPlayer(13769): MediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:40:12.647: E/(13769): IMediaPlayer::setVideoRect(0,25, 1280, 720)
08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): HTTP/1.1 206 Partial Content

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Date: Mon, 27 Aug 2012 02:33:24 GMT

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Server: Apache

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): X-Mod-H264-Streaming: version=2.2.7

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Last-Modified: Wed, 15 Aug 2012 06:24:38 GMT

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Accept-Ranges: bytes

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Cache-Control: max-age=315360000

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Expires: Thu, 25 Aug 2022 02:33:24 GMT

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Content-Type: video/mp4

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Powered-By-ChinaCache: HIT from 01006613Y4

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Content-Range: bytes 1000320-8311865/8311866

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Content-Length: 7311546

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Age: 409

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769): Powered-By-ChinaCache: HIT from 01075913r4

08-27 10:40:12.962: E/HttpGetProxy ~~~~(13769):

08-27 10:40:14.037: E/testVideoPlayer(13769): 預加載開關:true,等待緩衝時間:8000,首次緩衝時間:3261

本文的源碼可以到這裏下載：http://download.csdn.net/detail/hcb1230/6593579

HttpGetProxy.java源碼如下，可以讀出大概的運行流程：

public class HttpGetProxy{
	final static public int SIZE =  (int) (3 * 1024 * 1024);
	final static public String TAG = "HttpGetProxy";
	/** 鏈接帶的端口 */
	private int remotePort=-1;
	/** 遠程服務器地址 */
	private String remoteHost;
	/** 代理服務器使用的端口 */
	private int localPort;
	/** 本地服務器地址 */
	private String localHost;
	private ServerSocket localServer = null;
	/** 收發Media Player請求的Socket */
	private Socket sckPlayer = null;
	/** 收發Media Server請求的Socket */
	private Socket sckServer = null;
	/**服務器的Address*/
	private SocketAddress serverAddress;
	
	/**下載線程*/
	private DownloadThread download = null;
	
	/**
	 * 初始化代理服務器
	 * @param localport 代理服務器監聽的端口
	 */
	public HttpGetProxy(int localport) {
		try {
			localPort = localport;
			localHost = C.LOCAL_IP_ADDRESS;
			localServer = new ServerSocket(localport, 1,InetAddress.getByName(localHost));
		} catch (Exception e) {
			System.exit(0);
		}
	}

	/**
	 * 把URL提前下載在SD卡，實現預加載
	 * @param urlString
	 * @return 返回預加載文件名
	 * @throws Exception
	 */
	public String prebuffer(String urlString,int size) throws Exception{
		if(download!=null && download.isDownloading())
			download.stopThread(true);
		
		URI tmpURI=new URI(urlString);
		String fileName=Utils.urlToFileName(tmpURI.getPath());
		String filePath=C.getBufferDir()+"/"+fileName;
		
		download=new DownloadThread(urlString,filePath,size);
		download.startThread();
		
		return filePath;
	}
	
	/**
	 * 把網絡URL轉爲本地URL，127.0.0.1替換網絡域名
	 * 
	 * @param url網絡URL
	 * @return [0]:重定向後MP4真正URL，[1]:本地URL
	 */
	public String[] getLocalURL(String urlString) {
		
		// ----排除HTTP特殊----//
		String targetUrl = Utils.getRedirectUrl(urlString);
		// ----獲取對應本地代理服務器的鏈接----//
		String localUrl = null;
		URI originalURI = URI.create(targetUrl);
		remoteHost = originalURI.getHost();
		if (originalURI.getPort() != -1) {// URL帶Port
			serverAddress = new InetSocketAddress(remoteHost, originalURI.getPort());// 使用默認端口
			remotePort = originalURI.getPort();// 保存端口，中轉時替換
			localUrl = targetUrl.replace(
					remoteHost + ":" + originalURI.getPort(), localHost + ":"
							+ localPort);
		} else {// URL不帶Port
			serverAddress = new InetSocketAddress(remoteHost, C.HTTP_PORT);// 使用80端口
			remotePort = -1;
			localUrl = targetUrl.replace(remoteHost, localHost + ":"
					+ localPort);
		}
		
		String[] result= new String[]{targetUrl,localUrl};
		return result;
	}

	/**
	 * 異步啓動代理服務器
	 * 
	 * @throws IOException
	 */
	public void asynStartProxy() {
		new Thread() {
			public void run() {
				startProxy();
			}
		}.start();
	}

	private void startProxy() {
		HttpParser httpParser =null;
		HttpGetProxyUtils utils=null;
		int bytes_read;
	
		byte[] local_request = new byte[1024];
		byte[] remote_reply = new byte[1024];

		while (true) {
			boolean sentResponseHeader = false;
			try {// 開始新的request之前關閉過去的Socket
				if (sckPlayer != null)
					sckPlayer.close();
				if (sckServer != null)
					sckServer.close();
			} catch (IOException e1) {}
			try {
				// --------------------------------------
				// 監聽MediaPlayer的請求，MediaPlayer->代理服務器
				// --------------------------------------
				sckPlayer = localServer.accept();
				Log.e(TAG,"------------------------------------------------------------------");
				if(download!=null && download.isDownloading())
					download.stopThread(false);
				
				httpParser=new HttpParser(remoteHost,remotePort,localHost,localPort);
				utils = new HttpGetProxyUtils(sckPlayer,sckServer,serverAddress);
				
				ProxyRequest request = null;
				while ((bytes_read = sckPlayer.getInputStream().read(local_request)) != -1) {
					byte[] buffer=httpParser.getRequestBody(local_request,bytes_read);
					if(buffer!=null){
						request=httpParser.getProxyRequest(buffer);
						break;
					}
				}
				
				boolean isExists=new File(request._prebufferFilePath).exists();
				if(isExists)
					Log.e(TAG,"prebuffer size:"+download.getDownloadedSize());
				
				sckServer = utils.sentToServer(request._body);
				// ------------------------------------------------------
				// 把網絡服務器的反饋發到MediaPlayer，網絡服務器->代理服務器->MediaPlayer
				// ------------------------------------------------------
				while ((bytes_read = sckServer.getInputStream().read(remote_reply)) != -1) {
					if(sentResponseHeader){
						try{//拖動進度條時，容易在此異常，斷開重連
							utils.sendToMP(remote_reply,bytes_read);
						}catch (Exception e) {
							break;//發送異常直接退出while
						}
						continue;//退出本次while
					}

					List<byte[]> httpResponse = httpParser.getResponseBody(remote_reply, bytes_read);
					if (httpResponse.size() == 0)
						continue;//沒Header則退出本次循環

					sentResponseHeader = true;
					String responseStr = new String(httpResponse.get(0));
					Log.e(TAG + "<---", responseStr);
					//send http header to mediaplayer
					utils.sendToMP(httpResponse.get(0));
					
					if (isExists) {//需要發送預加載到MediaPlayer
						isExists = false;
						int sentBufferSize = 0;
						try{
							sentBufferSize = utils.sendPrebufferToMP(
								request._prebufferFilePath,
								request._rangePosition);
						}catch(Exception ex){
							break;
						}
						if (sentBufferSize > 0) {// 成功發送預加載，重新發送請求到服務器
							int newRange=(int) (sentBufferSize + request._rangePosition);
							String newRequestStr = httpParser.modifyRequestRange(request._body,newRange);
							Log.e(TAG + "-pre->", newRequestStr);
							//修改Range後的Request發送給服務器
							sckServer = utils.sentToServer(newRequestStr);
							//把服務器的Response的Header去掉
							utils.removeResponseHeader(httpParser);
							continue;
						}
					}

					// 發送剩餘數據
					if (httpResponse.size() == 2) {
						utils.sendToMP(httpResponse.get(1));
					}
				}

				Log.e(TAG, ".........over..........");

				// 關閉 2個SOCKET
				sckPlayer.close();
				sckServer.close();
			} catch (Exception e) {
				Log.e(TAG,e.toString());
				Log.e(TAG,Utils.getExceptionMessage(e));
			}
		}
	}

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