diff --git a/include/ndk/NdkMediaCodec.h b/include/ndk/NdkMediaCodec.h
index dd869f6..2f000d7 100644
--- a/include/ndk/NdkMediaCodec.h
+++ b/include/ndk/NdkMediaCodec.h
@@ -146,10 +146,22 @@
 AMediaFormat* AMediaCodec_getOutputFormat(AMediaCodec*);
 
 /**
- * Release and optionally render the specified buffer.
+ * If you are done with a buffer, use this call to return the buffer to
+ * the codec. If you previously specified a surface when configuring this
+ * video decoder you can optionally render the buffer.
  */
 media_status_t AMediaCodec_releaseOutputBuffer(AMediaCodec*, size_t idx, bool render);
 
+/**
+ * If you are done with a buffer, use this call to update its surface timestamp
+ * and return it to the codec to render it on the output surface. If you
+ * have not specified an output surface when configuring this video codec,
+ * this call will simply return the buffer to the codec.
+ *
+ * For more details, see the Java documentation for MediaCodec.releaseOutputBuffer.
+ */
+media_status_t AMediaCodec_releaseOutputBufferAtTime(
+        AMediaCodec *mData, size_t idx, int64_t timestampNs);
 
 typedef void (*OnCodecEvent)(AMediaCodec *codec, void *userdata);
 
@@ -163,20 +175,30 @@
         AMediaCodec*, OnCodecEvent callback, void *userdata);
 
 
-enum {
+typedef enum {
     AMEDIACODECRYPTOINFO_MODE_CLEAR = 0,
     AMEDIACODECRYPTOINFO_MODE_AES_CTR = 1
-};
+} cryptoinfo_mode_t;
 
 /**
- * create an AMediaCodecCryptoInfo from scratch. Use this if you need to use custom
+ * Create an AMediaCodecCryptoInfo from scratch. Use this if you need to use custom
  * crypto info, rather than one obtained from AMediaExtractor.
+ *
+ * AMediaCodecCryptoInfo describes the structure of an (at least
+ * partially) encrypted input sample.
+ * A buffer's data is considered to be partitioned into "subsamples",
+ * each subsample starts with a (potentially empty) run of plain,
+ * unencrypted bytes followed by a (also potentially empty) run of
+ * encrypted bytes.
+ * numBytesOfClearData can be null to indicate that all data is encrypted.
+ * This information encapsulates per-sample metadata as outlined in
+ * ISO/IEC FDIS 23001-7:2011 "Common encryption in ISO base media file format files".
  */
 AMediaCodecCryptoInfo *AMediaCodecCryptoInfo_new(
         int numsubsamples,
         uint8_t key[16],
         uint8_t iv[16],
-        uint32_t mode,
+        cryptoinfo_mode_t mode,
         size_t *clearbytes,
         size_t *encryptedbytes);
 
@@ -186,11 +208,35 @@
  */
 media_status_t AMediaCodecCryptoInfo_delete(AMediaCodecCryptoInfo*);
 
+/**
+ * The number of subsamples that make up the buffer's contents.
+ */
 size_t AMediaCodecCryptoInfo_getNumSubSamples(AMediaCodecCryptoInfo*);
+
+/**
+ * A 16-byte opaque key
+ */
 media_status_t AMediaCodecCryptoInfo_getKey(AMediaCodecCryptoInfo*, uint8_t *dst);
+
+/**
+ * A 16-byte initialization vector
+ */
 media_status_t AMediaCodecCryptoInfo_getIV(AMediaCodecCryptoInfo*, uint8_t *dst);
-uint32_t AMediaCodecCryptoInfo_getMode(AMediaCodecCryptoInfo*);
+
+/**
+ * The type of encryption that has been applied,
+ * one of AMEDIACODECRYPTOINFO_MODE_CLEAR or AMEDIACODECRYPTOINFO_MODE_AES_CTR.
+ */
+cryptoinfo_mode_t AMediaCodecCryptoInfo_getMode(AMediaCodecCryptoInfo*);
+
+/**
+ * The number of leading unencrypted bytes in each subsample.
+ */
 media_status_t AMediaCodecCryptoInfo_getClearBytes(AMediaCodecCryptoInfo*, size_t *dst);
+
+/**
+ * The number of trailing encrypted bytes in each subsample.
+ */
 media_status_t AMediaCodecCryptoInfo_getEncryptedBytes(AMediaCodecCryptoInfo*, size_t *dst);
 
 #ifdef __cplusplus
diff --git a/include/ndk/NdkMediaCrypto.h b/include/ndk/NdkMediaCrypto.h
index 83eaad2..90374c5 100644
--- a/include/ndk/NdkMediaCrypto.h
+++ b/include/ndk/NdkMediaCrypto.h
@@ -29,6 +29,7 @@
 #define _NDK_MEDIA_CRYPTO_H
 
 #include <sys/types.h>
+#include <stdbool.h>
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/include/ndk/NdkMediaExtractor.h b/include/ndk/NdkMediaExtractor.h
index 2ba69fb..5a319d7 100644
--- a/include/ndk/NdkMediaExtractor.h
+++ b/include/ndk/NdkMediaExtractor.h
@@ -114,6 +114,16 @@
  */
 bool AMediaExtractor_advance(AMediaExtractor*);
 
+typedef enum {
+    AMEDIAEXTRACTOR_SEEK_PREVIOUS_SYNC,
+    AMEDIAEXTRACTOR_SEEK_NEXT_SYNC,
+    AMEDIAEXTRACTOR_SEEK_CLOSEST_SYNC
+} SeekMode;
+
+/**
+ *
+ */
+media_status_t AMediaExtractor_seekTo(AMediaExtractor*, int64_t seekPosUs, SeekMode mode);
 
 /**
  * mapping of crypto scheme uuid to the scheme specific data for that scheme
@@ -146,7 +156,6 @@
     AMEDIAEXTRACTOR_SAMPLE_FLAG_ENCRYPTED = 2,
 };
 
-
 #ifdef __cplusplus
 } // extern "C"
 #endif
diff --git a/include/ndk/NdkMediaMuxer.h b/include/ndk/NdkMediaMuxer.h
index db183e9..1ddc51d 100644
--- a/include/ndk/NdkMediaMuxer.h
+++ b/include/ndk/NdkMediaMuxer.h
@@ -56,16 +56,59 @@
  */
 media_status_t AMediaMuxer_delete(AMediaMuxer*);
 
-media_status_t AMediaMuxer_setLocation(AMediaMuxer*, float latitude, float longtitude);
+/**
+ * Set and store the geodata (latitude and longitude) in the output file.
+ * This method should be called before AMediaMuxer_start. The geodata is stored
+ * in udta box if the output format is AMEDIAMUXER_OUTPUT_FORMAT_MPEG_4, and is
+ * ignored for other output formats.
+ * The geodata is stored according to ISO-6709 standard.
+ *
+ * Both values are specified in degrees.
+ * Latitude must be in the range [-90, 90].
+ * Longitude must be in the range [-180, 180].
+ */
+media_status_t AMediaMuxer_setLocation(AMediaMuxer*, float latitude, float longitude);
 
+/**
+ * Sets the orientation hint for output video playback.
+ * This method should be called before AMediaMuxer_start. Calling this
+ * method will not rotate the video frame when muxer is generating the file,
+ * but add a composition matrix containing the rotation angle in the output
+ * video if the output format is AMEDIAMUXER_OUTPUT_FORMAT_MPEG_4, so that a
+ * video player can choose the proper orientation for playback.
+ * Note that some video players may choose to ignore the composition matrix
+ * during playback.
+ * The angle is specified in degrees, clockwise.
+ * The supported angles are 0, 90, 180, and 270 degrees.
+ */
 media_status_t AMediaMuxer_setOrientationHint(AMediaMuxer*, int degrees);
 
+/**
+ * Adds a track with the specified format.
+ * Returns the index of the new track or a negative value in case of failure,
+ * which can be interpreted as a media_status_t.
+ */
 ssize_t AMediaMuxer_addTrack(AMediaMuxer*, const AMediaFormat* format);
 
+/**
+ * Start the muxer. Should be called after AMediaMuxer_addTrack and
+ * before AMediaMuxer_writeSampleData.
+ */
 media_status_t AMediaMuxer_start(AMediaMuxer*);
 
+/**
+ * Stops the muxer.
+ * Once the muxer stops, it can not be restarted.
+ */
 media_status_t AMediaMuxer_stop(AMediaMuxer*);
 
+/**
+ * Writes an encoded sample into the muxer.
+ * The application needs to make sure that the samples are written into
+ * the right tracks. Also, it needs to make sure the samples for each track
+ * are written in chronological order (e.g. in the order they are provided
+ * by the encoder.)
+ */
 media_status_t AMediaMuxer_writeSampleData(AMediaMuxer *muxer,
         size_t trackIdx, const uint8_t *data, const AMediaCodecBufferInfo &info);
 
diff --git a/media/ndk/NdkMediaCodec.cpp b/media/ndk/NdkMediaCodec.cpp
index 9e2aa67..bd2541f 100644
--- a/media/ndk/NdkMediaCodec.cpp
+++ b/media/ndk/NdkMediaCodec.cpp
@@ -341,6 +341,13 @@
 }
 
 EXPORT
+media_status_t AMediaCodec_releaseOutputBufferAtTime(
+        AMediaCodec *mData, size_t idx, int64_t timestampNs) {
+    ALOGV("render @ %lld", timestampNs);
+    return translate_error(mData->mCodec->renderOutputBufferAndRelease(idx, timestampNs));
+}
+
+EXPORT
 media_status_t AMediaCodec_setNotificationCallback(AMediaCodec *mData, OnCodecEvent callback, void *userdata) {
     mData->mCallback = callback;
     mData->mCallbackUserData = userdata;
@@ -351,7 +358,7 @@
         int numsubsamples;
         uint8_t key[16];
         uint8_t iv[16];
-        uint32_t mode;
+        cryptoinfo_mode_t mode;
         size_t *clearbytes;
         size_t *encryptedbytes;
 } AMediaCodecCryptoInfo;
@@ -396,7 +403,7 @@
         int numsubsamples,
         uint8_t key[16],
         uint8_t iv[16],
-        uint32_t mode,
+        cryptoinfo_mode_t mode,
         size_t *clearbytes,
         size_t *encryptedbytes) {
 
@@ -459,9 +466,9 @@
 }
 
 EXPORT
-uint32_t AMediaCodecCryptoInfo_getMode(AMediaCodecCryptoInfo* ci) {
+cryptoinfo_mode_t AMediaCodecCryptoInfo_getMode(AMediaCodecCryptoInfo* ci) {
     if (!ci) {
-        return AMEDIA_ERROR_INVALID_OBJECT;
+        return (cryptoinfo_mode_t) AMEDIA_ERROR_INVALID_OBJECT;
     }
     return ci->mode;
 }
diff --git a/media/ndk/NdkMediaExtractor.cpp b/media/ndk/NdkMediaExtractor.cpp
index 563358f..b0a9590 100644
--- a/media/ndk/NdkMediaExtractor.cpp
+++ b/media/ndk/NdkMediaExtractor.cpp
@@ -150,6 +150,20 @@
 }
 
 EXPORT
+media_status_t AMediaExtractor_seekTo(AMediaExtractor *ex, int64_t seekPosUs, SeekMode mode) {
+    android::MediaSource::ReadOptions::SeekMode sfmode;
+    if (mode == AMEDIAEXTRACTOR_SEEK_PREVIOUS_SYNC) {
+        sfmode = android::MediaSource::ReadOptions::SEEK_PREVIOUS_SYNC;
+    } else if (mode == AMEDIAEXTRACTOR_SEEK_CLOSEST_SYNC) {
+        sfmode = android::MediaSource::ReadOptions::SEEK_CLOSEST_SYNC;
+    } else {
+        sfmode = android::MediaSource::ReadOptions::SEEK_NEXT_SYNC;
+    }
+
+    return translate_error(ex->mImpl->seekTo(seekPosUs, sfmode));
+}
+
+EXPORT
 ssize_t AMediaExtractor_readSampleData(AMediaExtractor *mData, uint8_t *buffer, size_t capacity) {
     //ALOGV("readSampleData");
     sp<ABuffer> tmp = new ABuffer(buffer, capacity);
@@ -331,7 +345,7 @@
             numSubSamples,
             (uint8_t*) key,
             (uint8_t*) iv,
-            mode,
+            (cryptoinfo_mode_t) mode,
             (size_t*) cleardata,
             (size_t*) crypteddata);
 }