Readahead support

res/values/translatable.xml

@@ -164,6 +164,9 @@ THE SOFTWARE.
 	<string name="replaygain_untagged_debump_title">Songs without Replay Gain tag</string>
 	<string name="replaygain_untagged_debump_summary">Decrease volume by</string>
 
+	<string name="readahead">Enable readahead</string>
+	<string name="readahead_summary">Readahead the currently playing song. This option may solve \'audio dropout\' issues. (caused by a slow SD card)</string>
+
 	<string name="notifications">Notifications</string>
 	<string name="notification_mode_title">Notification Mode</string>
 	<string name="notification_action_title">Notification Action</string>

res/xml/preference_audio.xml

@@ -43,6 +43,11 @@ THE SOFTWARE.
 		android:title="@string/headset_pause_title"
 		android:defaultValue="true"
 		android:summary="@string/headset_pause_summary" />
+	<CheckBoxPreference
+		android:key="enable_readahead"
+		android:title="@string/readahead"
+		android:defaultValue="false"
+		android:summary="@string/readahead_summary" />
 	<PreferenceScreen
 		android:title="@string/replaygain"
 		android:summary="@string/replaygain_summary">

src/ch/blinkenlights/android/vanilla/PlaybackService.java

@@ -373,7 +373,17 @@ public final class PlaybackService extends Service
 	private boolean mReplayGainAlbumEnabled;
 	private int mReplayGainBump;
 	private int mReplayGainUntaggedDeBump;
-	
+	/**
+	 * TRUE if the readahead feature is enabled
+	 */
+	private boolean mReadaheadEnabled;
+	/**
+	 * Reference to precreated ReadAhead thread
+	 */
+	private ReadaheadThread mReadahead;
+	/**
+	 * Reference to precreated BASTP Object
+	 */
 	private BastpUtil mBastpUtil;
 	
 	@Override
@@ -388,6 +398,8 @@ public final class PlaybackService extends Service
 
 		mMediaPlayer = getNewMediaPlayer();
 		mBastpUtil = new BastpUtil();
+		mReadahead = new ReadaheadThread();
+		mReadahead.start();
 		
 		mNotificationManager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
 		mAudioManager = (AudioManager)getSystemService(AUDIO_SERVICE);
@@ -413,6 +425,8 @@ public final class PlaybackService extends Service
 		mReplayGainBump = settings.getInt(PrefKeys.REPLAYGAIN_BUMP, 75);  /* seek bar is 150 -> 75 == middle == 0 */
 		mReplayGainUntaggedDeBump = settings.getInt(PrefKeys.REPLAYGAIN_UNTAGGED_DEBUMP, 150); /* seek bar is 150 -> == 0 */
 
+		mReadaheadEnabled = settings.getBoolean(PrefKeys.ENABLE_READAHEAD, false);
+
 		PowerManager powerManager = (PowerManager)getSystemService(POWER_SERVICE);
 		mWakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "VanillaMusicLock");
 
@@ -646,6 +660,10 @@ public final class PlaybackService extends Service
 		mp.setVolume(rg_result, rg_result);
 	}
 
+	/**
+	 * Returns the (hopefully cached) replaygain 
+	 * values of given file
+	 */
 	public float[] getReplayGainValues(String path) {
 		return mBastpUtil.getReplayGainValues(path);
 	}
@@ -691,7 +709,18 @@ public final class PlaybackService extends Service
 		else {
 			Log.d("VanillaMusic", "Must not create new media player object");
 		}
+	}
 
+	/**
+	 * Stops or starts the readahead thread
+	 */
+	private void triggerReadAhead() {
+		Song song = mCurrentSong;
+		if(mReadaheadEnabled && (mState & FLAG_PLAYING) != 0 && song != null) {
+			mReadahead.setSource(song.path);
+		} else {
+			mReadahead.pause();
+		}
 	}
 
 	/**
@@ -773,6 +802,8 @@ public final class PlaybackService extends Service
 		} else if (PrefKeys.REPLAYGAIN_UNTAGGED_DEBUMP.equals(key)) {
 			mReplayGainUntaggedDeBump = settings.getInt(PrefKeys.REPLAYGAIN_UNTAGGED_DEBUMP, 150);
 			refreshReplayGainValues();
+		} else if (PrefKeys.ENABLE_READAHEAD.equals(key)) {
+			mReadaheadEnabled = settings.getBoolean(PrefKeys.ENABLE_READAHEAD, false);
 		}
 
 		CompatFroyo.dataChanged(this);
@@ -898,6 +929,7 @@ public final class PlaybackService extends Service
 			mTimeline.setFinishAction(finishAction(state));
 		
 		triggerGaplessUpdate();
+		triggerReadAhead();
 	}
 
 	private void broadcastChange(int state, Song song, long uptime)
@@ -1169,6 +1201,7 @@ public final class PlaybackService extends Service
 			
 			mMediaPlayerInitialized = true;
 			triggerGaplessUpdate();
+			triggerReadAhead();
 			
 			if (mPendingSeek != 0 && mPendingSeekSong == song.id) {
 				mMediaPlayer.seekTo(mPendingSeek);

src/ch/blinkenlights/android/vanilla/PrefKeys.java

@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2013 Adrian Ulrich <adrian@blinkenlights.ch>
  * Copyright (C) 2012 Christopher Eby <kreed@kreed.org>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -60,4 +61,5 @@ public class PrefKeys {
 	public static final String ENABLE_ALBUM_REPLAYGAIN = "enable_album_replaygain";
 	public static final String REPLAYGAIN_BUMP = "replaygain_bump";
 	public static final String REPLAYGAIN_UNTAGGED_DEBUMP = "replaygain_untagged_debump";
+	public static final String ENABLE_READAHEAD = "enable_readahead";
 }

src/ch/blinkenlights/android/vanilla/ReadaheadThread.java

@@ -0,0 +1,130 @@
+/*
+ * Copyright (C) 2013 Adrian Ulrich <adrian@blinkenlights.ch>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>. 
+ */
+
+
+package ch.blinkenlights.android.vanilla;
+
+import android.util.Log;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+class ReadaheadThread extends Thread {
+	private String mCurrentPath = null;
+	private boolean mPaused = true;
+	private Thread mThread;
+
+
+	public ReadaheadThread() {
+	}
+
+	/**
+	 * Starts the persistent RA-Thread. This thread is never stopped: Destroying + creating
+	 * a new thread just because the user clicked on 'pause' doesn't make much sense
+	 */
+	public void start() {
+		mThread = new Thread(new Runnable() {
+			public void run() {
+				threadWorker();
+			}
+		});
+		mThread.start();
+	}
+
+	/**
+	 * Updates the current read-ahead source and wakes up the ra-thread
+	 */
+	public void setSource(String path) {
+		mCurrentPath = path;
+		mPaused = false;
+		mThread.interrupt();
+	}
+
+	/**
+	 * Tells the ra-thread to pause the read-ahead work
+	 * Calling setSource with path = mCurrentPath will cause the
+	 * thread to RESUME (the file is not closed by calling pause())
+	 */
+	public void pause() {
+		mPaused = true;
+	}
+
+	/**
+	 * Sleep for x milli seconds
+	 */
+	private static void sleep(int millis) {
+		try { Thread.sleep(millis); }
+		catch(InterruptedException e) {}
+	}
+
+	/**
+	 * Our thread mainloop
+	 * This thread will read from mCurrentPath until
+	 * we hit an EOF or mPaused is set to false.
+	 * The readahead speed is controlled by 'sleepTime'
+	 */
+	private void threadWorker() {
+		String path = null;
+		FileInputStream fis = null;
+		byte[] scratch = new byte[8192];             // Read 8kB per call to read()
+		int sleepTime = (int)((1f/(256f/8f))*1000f); // We try to read 256kB/s (with 8kB blocks)
+
+		for(;;) {
+			if(mPaused) {
+				sleep(600*1000); /* Sleep 10 minutes */
+				continue;
+			}
+
+			if(path != mCurrentPath) {
+				// File changed: First we try to close the old FIS
+				// fis can be null or already closed, we therefore do
+				// not care about the result. (the GC would take care of it anyway)
+				try { fis.close(); } catch(Exception e) {}
+				// We can now try to open the new file.
+				// Errors are not fatal, we will simply switch into paused-mode
+				try {
+					fis = new FileInputStream(mCurrentPath);
+					path = mCurrentPath;
+					Log.v("VanillaMusic", "readahead of "+path+" starts");
+				} catch(FileNotFoundException e) {
+					path = null;
+					mPaused = true;
+					continue;
+				}
+			}
+
+			// 'fis' is now an open FileInputStream. Read 8kB per go until
+			// we hit EOF
+			try {
+				int br = fis.read(scratch);
+				if(br < 0) { // no more data -> EOF
+					mPaused = true;
+					Log.v("VanillaMusic", "readahead of "+path+" finished");
+				}
+			} catch(IOException e) {
+				path = null; // io error?! switch into paused mode
+				mPaused = true;
+			}
+			sleep(sleepTime);
+		}
+	}
+	
+}