diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index d2b6d85b988..aabccf11d33 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -41,8 +41,8 @@
   * Upgrade Truth dependency from 0.44 to 1.0.
   * Upgrade to JUnit 4.13-rc-2.
 * UI
-  * move logic of prev, next, fast forward and rewind to ControlDispatcher
-  [#6926](https://github.com/google/ExoPlayer/issues/6926)).
+  * Move logic of prev, next, fast forward and rewind to ControlDispatcher
+    ([#6926](https://github.com/google/ExoPlayer/issues/6926)).
 * Demo apps: Add
   [GL demo app](https://github.com/google/ExoPlayer/tree/dev-v2/demos/gl) to
   show how to render video to a `GLSurfaceView` while applying a GL shader.
@@ -101,6 +101,8 @@
   on earlier releases, but only when embedded in a non-FLAC container such as
   Matroska or MP4.
 * Add support for ID3 genres added in Wimamp 5.6 (2010).
+* DRM: Fix `NullPointerException` when playing DRM-protected content
+  ([#6951](https://github.com/google/ExoPlayer/issues/6951)).
 
 ### 2.11.1 (2019-12-20) ###
 
diff --git a/demos/main/src/main/assets/media.exolist.json b/demos/main/src/main/assets/media.exolist.json
index 06f063b1c13..26ed0446d0c 100644
--- a/demos/main/src/main/assets/media.exolist.json
+++ b/demos/main/src/main/assets/media.exolist.json
@@ -3,9 +3,8 @@
     "name": "YouTube DASH",
     "samples": [
       {
-        "name": "Google Glass (MP4,H264)",
-        "uri": "https://www.youtube.com/api/manifest/dash/id/bf5bb2419360daf1/source/youtube?as=fmp4_audio_clear,fmp4_sd_hd_clear&sparams=ip,ipbits,expire,source,id,as&ip=0.0.0.0&ipbits=0&expire=19000000000&signature=51AF5F39AB0CEC3E5497CD9C900EBFEAECCCB5C7.8506521BFC350652163895D4C26DEE124209AA9E&key=ik0",
-        "extension": "mpd"
+        "name": "6956",
+        "uri": "http://master255.org/res/%d0%9a%d0%bb%d0%b8%d0%bf%d1%8b/B/Billy%20Mack/Billy%20Mack%20-%20Christmas%20Is%20All%20Around.mpg"
       },
       {
         "name": "Google Play (MP4,H264)",
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/audio/SimpleDecoderAudioRenderer.java b/library/core/src/main/java/com/google/android/exoplayer2/audio/SimpleDecoderAudioRenderer.java
index 2f324dba02b..1bca34479b6 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/audio/SimpleDecoderAudioRenderer.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/audio/SimpleDecoderAudioRenderer.java
@@ -97,6 +97,7 @@ public abstract class SimpleDecoderAudioRenderer extends BaseRenderer implements
   private final AudioSink audioSink;
   private final DecoderInputBuffer flagsOnlyBuffer;
 
+  private boolean drmResourcesAcquired;
   private DecoderCounters decoderCounters;
   private Format inputFormat;
   private int encoderDelay;
@@ -543,6 +544,10 @@ public PlaybackParameters getPlaybackParameters() {
 
   @Override
   protected void onEnabled(boolean joining) throws ExoPlaybackException {
+    if (drmSessionManager != null && !drmResourcesAcquired) {
+      drmResourcesAcquired = true;
+      drmSessionManager.prepare();
+    }
     decoderCounters = new DecoderCounters();
     eventDispatcher.enabled(decoderCounters);
     int tunnelingAudioSessionId = getConfiguration().tunnelingAudioSessionId;
@@ -591,6 +596,14 @@ protected void onDisabled() {
     }
   }
 
+  @Override
+  protected void onReset() {
+    if (drmSessionManager != null && drmResourcesAcquired) {
+      drmResourcesAcquired = false;
+      drmSessionManager.release();
+    }
+  }
+
   @Override
   public void handleMessage(int messageType, @Nullable Object message) throws ExoPlaybackException {
     switch (messageType) {
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecRenderer.java b/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecRenderer.java
index f27d4909cb1..bd0440ce2e7 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecRenderer.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecRenderer.java
@@ -371,6 +371,7 @@ private static String getDiagnosticInfoV21(Throwable cause) {
   private final ArrayList<Long> decodeOnlyPresentationTimestamps;
   private final MediaCodec.BufferInfo outputBufferInfo;
 
+  private boolean drmResourcesAcquired;
   @Nullable private Format inputFormat;
   private Format outputFormat;
   @Nullable private DrmSession<FrameworkMediaCrypto> codecDrmSession;
@@ -659,6 +660,10 @@ protected final MediaCodecInfo getCodecInfo() {
 
   @Override
   protected void onEnabled(boolean joining) throws ExoPlaybackException {
+    if (drmSessionManager != null && !drmResourcesAcquired) {
+      drmResourcesAcquired = true;
+      drmSessionManager.prepare();
+    }
     decoderCounters = new DecoderCounters();
   }
 
@@ -705,6 +710,10 @@ protected void onReset() {
     } finally {
       setSourceDrmSession(null);
     }
+    if (drmSessionManager != null && drmResourcesAcquired) {
+      drmResourcesAcquired = false;
+      drmSessionManager.release();
+    }
   }
 
   protected void releaseCodec() {
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/video/SimpleDecoderVideoRenderer.java b/library/core/src/main/java/com/google/android/exoplayer2/video/SimpleDecoderVideoRenderer.java
index bf0a28ffa0c..6d8147b012e 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/video/SimpleDecoderVideoRenderer.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/video/SimpleDecoderVideoRenderer.java
@@ -77,6 +77,7 @@ public abstract class SimpleDecoderVideoRenderer extends BaseRenderer {
   private final DecoderInputBuffer flagsOnlyBuffer;
   private final DrmSessionManager<ExoMediaCrypto> drmSessionManager;
 
+  private boolean drmResourcesAcquired;
   private Format inputFormat;
   private Format outputFormat;
   private SimpleDecoder<
@@ -237,6 +238,10 @@ public boolean isReady() {
 
   @Override
   protected void onEnabled(boolean joining) throws ExoPlaybackException {
+    if (drmSessionManager != null && !drmResourcesAcquired) {
+      drmResourcesAcquired = true;
+      drmSessionManager.prepare();
+    }
     decoderCounters = new DecoderCounters();
     eventDispatcher.enabled(decoderCounters);
   }
@@ -286,6 +291,14 @@ protected void onDisabled() {
     }
   }
 
+  @Override
+  protected void onReset() {
+    if (drmSessionManager != null && drmResourcesAcquired) {
+      drmResourcesAcquired = false;
+      drmSessionManager.release();
+    }
+  }
+
   @Override
   protected void onStreamChanged(Format[] formats, long offsetUs) throws ExoPlaybackException {
     outputStreamOffsetUs = offsetUs;