Merge changes from topic "b113052379-cp-from-pi-dev-p2"

* changes:
  Camera: Documentation update to remove physicalIds
  Camera: Documentation updates for calibration and distortion correction
  Fix NdkImage.h includes
  Restore __ANDROID_API__ guards for camera/media headers
  Remove __INTRODUCED_IN from a typedef
diff --git a/camera/ndk/include/camera/NdkCameraCaptureSession.h b/camera/ndk/include/camera/NdkCameraCaptureSession.h
index 9bf8247..5e0db60 100644
--- a/camera/ndk/include/camera/NdkCameraCaptureSession.h
+++ b/camera/ndk/include/camera/NdkCameraCaptureSession.h
@@ -45,6 +45,8 @@
 
 __BEGIN_DECLS
 
+#if __ANDROID_API__ >= 24
+
 /**
  * ACameraCaptureSession is an opaque type that manages frame captures of a camera device.
  *
@@ -591,6 +593,10 @@
 camera_status_t ACameraCaptureSession_abortCaptures(ACameraCaptureSession* session)
         __INTRODUCED_IN(24);
 
+#endif /* __ANDROID_API__ >= 24 */
+
+#if __ANDROID_API__ >= 28
+
 typedef struct ACaptureSessionOutput ACaptureSessionOutput;
 
 /**
@@ -635,6 +641,7 @@
  */
 camera_status_t ACameraCaptureSession_updateSharedOutput(ACameraCaptureSession* session,
         ACaptureSessionOutput* output) __INTRODUCED_IN(28);
+#endif /* __ANDROID_API__ >= 28 */
 
 __END_DECLS
 
diff --git a/camera/ndk/include/camera/NdkCameraDevice.h b/camera/ndk/include/camera/NdkCameraDevice.h
index bdd27f9..7c13b34 100644
--- a/camera/ndk/include/camera/NdkCameraDevice.h
+++ b/camera/ndk/include/camera/NdkCameraDevice.h
@@ -44,6 +44,8 @@
 
 __BEGIN_DECLS
 
+#if __ANDROID_API__ >= 24
+
 /**
  * ACameraDevice is opaque type that provides access to a camera device.
  *
@@ -666,6 +668,10 @@
         const ACameraCaptureSession_stateCallbacks* callbacks,
         /*out*/ACameraCaptureSession** session) __INTRODUCED_IN(24);
 
+#endif /* __ANDROID_API__ >= 24 */
+
+#if __ANDROID_API__ >= 28
+
 /**
  * Create a shared ACaptureSessionOutput object.
  *
@@ -757,6 +763,8 @@
         const ACameraCaptureSession_stateCallbacks* callbacks,
         /*out*/ACameraCaptureSession** session) __INTRODUCED_IN(28);
 
+#endif /* __ANDROID_API__ >= 28 */
+
 __END_DECLS
 
 #endif /* _NDK_CAMERA_DEVICE_H */
diff --git a/camera/ndk/include/camera/NdkCameraError.h b/camera/ndk/include/camera/NdkCameraError.h
index e19ce36..6b58155 100644
--- a/camera/ndk/include/camera/NdkCameraError.h
+++ b/camera/ndk/include/camera/NdkCameraError.h
@@ -40,6 +40,8 @@
 
 __BEGIN_DECLS
 
+#if __ANDROID_API__ >= 24
+
 typedef enum {
     ACAMERA_OK = 0,
 
@@ -130,6 +132,8 @@
     ACAMERA_ERROR_PERMISSION_DENIED     = ACAMERA_ERROR_BASE - 13,
 } camera_status_t;
 
+#endif /* __ANDROID_API__ >= 24 */
+
 __END_DECLS
 
 #endif /* _NDK_CAMERA_ERROR_H */
diff --git a/camera/ndk/include/camera/NdkCameraManager.h b/camera/ndk/include/camera/NdkCameraManager.h
index a1cca4d..ea76738 100644
--- a/camera/ndk/include/camera/NdkCameraManager.h
+++ b/camera/ndk/include/camera/NdkCameraManager.h
@@ -44,6 +44,8 @@
 
 __BEGIN_DECLS
 
+#if __ANDROID_API__ >= 24
+
 /**
  * ACameraManager is opaque type that provides access to camera service.
  *
@@ -119,7 +121,7 @@
  *                 this callback returns.
  */
 typedef void (*ACameraManager_AvailabilityCallback)(void* context,
-        const char* cameraId) __INTRODUCED_IN(24);
+        const char* cameraId);
 
 /**
  * A listener for camera devices becoming available or unavailable to open.
@@ -274,6 +276,8 @@
         ACameraDevice_StateCallbacks* callback,
         /*out*/ACameraDevice** device) __INTRODUCED_IN(24);
 
+#endif /* __ANDROID_API__ >= 24 */
+
 __END_DECLS
 
 #endif /* _NDK_CAMERA_MANAGER_H */
diff --git a/camera/ndk/include/camera/NdkCameraMetadata.h b/camera/ndk/include/camera/NdkCameraMetadata.h
index 2078da7..611e270 100644
--- a/camera/ndk/include/camera/NdkCameraMetadata.h
+++ b/camera/ndk/include/camera/NdkCameraMetadata.h
@@ -44,6 +44,8 @@
 
 __BEGIN_DECLS
 
+#if __ANDROID_API__ >= 24
+
 /**
  * ACameraMetadata is opaque type that provides access to read-only camera metadata like camera
  * characteristics (via {@link ACameraManager_getCameraCharacteristics}) or capture results (via
@@ -229,6 +231,8 @@
  */
 void ACameraMetadata_free(ACameraMetadata* metadata) __INTRODUCED_IN(24);
 
+#endif /* __ANDROID_API__ >= 24 */
+
 __END_DECLS
 
 #endif /* _NDK_CAMERA_METADATA_H */
diff --git a/camera/ndk/include/camera/NdkCameraMetadataTags.h b/camera/ndk/include/camera/NdkCameraMetadataTags.h
index bd85469..c1f5ddc 100644
--- a/camera/ndk/include/camera/NdkCameraMetadataTags.h
+++ b/camera/ndk/include/camera/NdkCameraMetadataTags.h
@@ -40,6 +40,8 @@
 
 __BEGIN_DECLS
 
+#if __ANDROID_API__ >= 24
+
 typedef enum acamera_metadata_section {
     ACAMERA_COLOR_CORRECTION,
     ACAMERA_CONTROL,
@@ -2310,7 +2312,9 @@
      * <p>If this device is the largest or only camera device with a given facing, then this
      * position will be <code>(0, 0, 0)</code>; a camera device with a lens optical center located 3 cm
      * from the main sensor along the +X axis (to the right from the user's perspective) will
-     * report <code>(0.03, 0, 0)</code>.</p>
+     * report <code>(0.03, 0, 0)</code>.  Note that this means that, for many computer vision
+     * applications, the position needs to be negated to convert it to a translation from the
+     * camera to the origin.</p>
      * <p>To transform a pixel coordinates between two cameras facing the same direction, first
      * the source camera ACAMERA_LENS_DISTORTION must be corrected for.  Then the source
      * camera ACAMERA_LENS_INTRINSIC_CALIBRATION needs to be applied, followed by the
@@ -2322,7 +2326,8 @@
      * <p>To compare this against a real image from the destination camera, the destination camera
      * image then needs to be corrected for radial distortion before comparison or sampling.</p>
      * <p>When ACAMERA_LENS_POSE_REFERENCE is GYROSCOPE, then this position is relative to
-     * the center of the primary gyroscope on the device.</p>
+     * the center of the primary gyroscope on the device. The axis definitions are the same as
+     * with PRIMARY_CAMERA.</p>
      *
      * @see ACAMERA_LENS_DISTORTION
      * @see ACAMERA_LENS_INTRINSIC_CALIBRATION
@@ -2416,13 +2421,15 @@
      * </code></pre>
      * <p>which can then be combined with the camera pose rotation
      * <code>R</code> and translation <code>t</code> (ACAMERA_LENS_POSE_ROTATION and
-     * ACAMERA_LENS_POSE_TRANSLATION, respective) to calculate the
+     * ACAMERA_LENS_POSE_TRANSLATION, respectively) to calculate the
      * complete transform from world coordinates to pixel
      * coordinates:</p>
-     * <pre><code>P = [ K 0   * [ R t
-     *      0 1 ]     0 1 ]
+     * <pre><code>P = [ K 0   * [ R -Rt
+     *      0 1 ]      0 1 ]
      * </code></pre>
-     * <p>and with <code>p_w</code> being a point in the world coordinate system
+     * <p>(Note the negation of poseTranslation when mapping from camera
+     * to world coordinates, and multiplication by the rotation).</p>
+     * <p>With <code>p_w</code> being a point in the world coordinate system
      * and <code>p_s</code> being a point in the camera active pixel array
      * coordinate system, and with the mapping including the
      * homogeneous division by z:</p>
@@ -2444,6 +2451,13 @@
      * activeArraySize rectangle), to determine the final pixel
      * coordinate of the world point for processed (non-RAW)
      * output buffers.</p>
+     * <p>For camera devices, the center of pixel <code>(x,y)</code> is located at
+     * coordinate <code>(x + 0.5, y + 0.5)</code>.  So on a device with a
+     * precorrection active array of size <code>(10,10)</code>, the valid pixel
+     * indices go from <code>(0,0)-(9,9)</code>, and an perfectly-built camera would
+     * have an optical center at the exact center of the pixel grid, at
+     * coordinates <code>(5.0, 5.0)</code>, which is the top-left corner of pixel
+     * <code>(5,5)</code>.</p>
      *
      * @see ACAMERA_LENS_DISTORTION
      * @see ACAMERA_LENS_POSE_ROTATION
@@ -3057,7 +3071,7 @@
      * outputs will crop horizontally (pillarbox), and 16:9
      * streams will match exactly. These additional crops will
      * be centered within the crop region.</p>
-     * <p>If the coordinate system is android.sensor.info.activeArraysSize, the width and height
+     * <p>If the coordinate system is ACAMERA_SENSOR_INFO_ACTIVE_ARRAY_SIZE, the width and height
      * of the crop region cannot be set to be smaller than
      * <code>floor( activeArraySize.width / ACAMERA_SCALER_AVAILABLE_MAX_DIGITAL_ZOOM )</code> and
      * <code>floor( activeArraySize.height / ACAMERA_SCALER_AVAILABLE_MAX_DIGITAL_ZOOM )</code>, respectively.</p>
@@ -4673,8 +4687,8 @@
     ACAMERA_STATISTICS_LENS_SHADING_MAP_MODE =                  // byte (acamera_metadata_enum_android_statistics_lens_shading_map_mode_t)
             ACAMERA_STATISTICS_START + 16,
     /**
-     * <p>A control for selecting whether OIS position information is included in output
-     * result metadata.</p>
+     * <p>A control for selecting whether optical stabilization (OIS) position
+     * information is included in output result metadata.</p>
      *
      * <p>Type: byte (acamera_metadata_enum_android_statistics_ois_data_mode_t)</p>
      *
@@ -4684,6 +4698,12 @@
      *   <li>ACaptureRequest</li>
      * </ul></p>
      *
+     * <p>Since optical image stabilization generally involves motion much faster than the duration
+     * of individualq image exposure, multiple OIS samples can be included for a single capture
+     * result. For example, if the OIS reporting operates at 200 Hz, a typical camera operating
+     * at 30fps may have 6-7 OIS samples per capture result. This information can be combined
+     * with the rolling shutter skew to account for lens motion during image exposure in
+     * post-processing algorithms.</p>
      */
     ACAMERA_STATISTICS_OIS_DATA_MODE =                          // byte (acamera_metadata_enum_android_statistics_ois_data_mode_t)
             ACAMERA_STATISTICS_START + 17,
@@ -4715,11 +4735,15 @@
      * </ul></p>
      *
      * <p>The array contains the amount of shifts in x direction, in pixels, based on OIS samples.
-     * A positive value is a shift from left to right in active array coordinate system. For
-     * example, if the optical center is (1000, 500) in active array coordinates, a shift of
-     * (3, 0) puts the new optical center at (1003, 500).</p>
+     * A positive value is a shift from left to right in the pre-correction active array
+     * coordinate system. For example, if the optical center is (1000, 500) in pre-correction
+     * active array coordinates, a shift of (3, 0) puts the new optical center at (1003, 500).</p>
      * <p>The number of shifts must match the number of timestamps in
      * ACAMERA_STATISTICS_OIS_TIMESTAMPS.</p>
+     * <p>The OIS samples are not affected by whether lens distortion correction is enabled (on
+     * supporting devices). They are always reported in pre-correction active array coordinates,
+     * since the scaling of OIS shifts would depend on the specific spot on the sensor the shift
+     * is needed.</p>
      *
      * @see ACAMERA_STATISTICS_OIS_TIMESTAMPS
      */
@@ -4736,11 +4760,15 @@
      * </ul></p>
      *
      * <p>The array contains the amount of shifts in y direction, in pixels, based on OIS samples.
-     * A positive value is a shift from top to bottom in active array coordinate system. For
-     * example, if the optical center is (1000, 500) in active array coordinates, a shift of
-     * (0, 5) puts the new optical center at (1000, 505).</p>
+     * A positive value is a shift from top to bottom in pre-correction active array coordinate
+     * system. For example, if the optical center is (1000, 500) in active array coordinates, a
+     * shift of (0, 5) puts the new optical center at (1000, 505).</p>
      * <p>The number of shifts must match the number of timestamps in
      * ACAMERA_STATISTICS_OIS_TIMESTAMPS.</p>
+     * <p>The OIS samples are not affected by whether lens distortion correction is enabled (on
+     * supporting devices). They are always reported in pre-correction active array coordinates,
+     * since the scaling of OIS shifts would depend on the specific spot on the sensor the shift
+     * is needed.</p>
      *
      * @see ACAMERA_STATISTICS_OIS_TIMESTAMPS
      */
@@ -5430,16 +5458,34 @@
      * any correction at all would slow down capture rate.  Every output stream will have a
      * similar amount of enhancement applied.</p>
      * <p>The correction only applies to processed outputs such as YUV, JPEG, or DEPTH16; it is not
-     * applied to any RAW output. Metadata coordinates such as face rectangles or metering
-     * regions are also not affected by correction.</p>
+     * applied to any RAW output.</p>
      * <p>This control will be on by default on devices that support this control. Applications
      * disabling distortion correction need to pay extra attention with the coordinate system of
      * metering regions, crop region, and face rectangles. When distortion correction is OFF,
      * metadata coordinates follow the coordinate system of
      * ACAMERA_SENSOR_INFO_PRE_CORRECTION_ACTIVE_ARRAY_SIZE. When distortion is not OFF, metadata
-     * coordinates follow the coordinate system of ACAMERA_SENSOR_INFO_ACTIVE_ARRAY_SIZE.</p>
+     * coordinates follow the coordinate system of ACAMERA_SENSOR_INFO_ACTIVE_ARRAY_SIZE.  The
+     * camera device will map these metadata fields to match the corrected image produced by the
+     * camera device, for both capture requests and results.  However, this mapping is not very
+     * precise, since rectangles do not generally map to rectangles when corrected.  Only linear
+     * scaling between the active array and precorrection active array coordinates is
+     * performed. Applications that require precise correction of metadata need to undo that
+     * linear scaling, and apply a more complete correction that takes into the account the app's
+     * own requirements.</p>
+     * <p>The full list of metadata that is affected in this way by distortion correction is:</p>
+     * <ul>
+     * <li>ACAMERA_CONTROL_AF_REGIONS</li>
+     * <li>ACAMERA_CONTROL_AE_REGIONS</li>
+     * <li>ACAMERA_CONTROL_AWB_REGIONS</li>
+     * <li>ACAMERA_SCALER_CROP_REGION</li>
+     * <li>android.statistics.faces</li>
+     * </ul>
      *
+     * @see ACAMERA_CONTROL_AE_REGIONS
+     * @see ACAMERA_CONTROL_AF_REGIONS
+     * @see ACAMERA_CONTROL_AWB_REGIONS
      * @see ACAMERA_LENS_DISTORTION
+     * @see ACAMERA_SCALER_CROP_REGION
      * @see ACAMERA_SENSOR_INFO_ACTIVE_ARRAY_SIZE
      * @see ACAMERA_SENSOR_INFO_PRE_CORRECTION_ACTIVE_ARRAY_SIZE
      */
@@ -7171,11 +7217,11 @@
      * camera in the list of supported camera devices.</p>
      * <p>This capability requires the camera device to support the following:</p>
      * <ul>
-     * <li>This camera device must list the following static metadata entries in <a href="https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html">CameraCharacteristics</a>:<ul>
-     * <li>android.logicalMultiCamera.physicalIds</li>
-     * <li>ACAMERA_LOGICAL_MULTI_CAMERA_SENSOR_SYNC_TYPE</li>
-     * </ul>
-     * </li>
+     * <li>The IDs of underlying physical cameras are returned via
+     *   <a href="https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html#getPhysicalCameraIds">CameraCharacteristics#getPhysicalCameraIds</a>.</li>
+     * <li>This camera device must list static metadata
+     *   ACAMERA_LOGICAL_MULTI_CAMERA_SENSOR_SYNC_TYPE in
+     *   <a href="https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html">CameraCharacteristics</a>.</li>
      * <li>The underlying physical cameras' static metadata must list the following entries,
      *   so that the application can correlate pixels from the physical streams:<ul>
      * <li>ACAMERA_LENS_POSE_REFERENCE</li>
@@ -7894,6 +7940,9 @@
 
 } acamera_metadata_enum_android_distortion_correction_mode_t;
 
+
+#endif /* __ANDROID_API__ >= 24 */
+
 __END_DECLS
 
 #endif /* _NDK_CAMERA_METADATA_TAGS_H */
diff --git a/camera/ndk/include/camera/NdkCaptureRequest.h b/camera/ndk/include/camera/NdkCaptureRequest.h
index 2fb5d12..5340e76 100644
--- a/camera/ndk/include/camera/NdkCaptureRequest.h
+++ b/camera/ndk/include/camera/NdkCaptureRequest.h
@@ -44,6 +44,8 @@
 
 __BEGIN_DECLS
 
+#if __ANDROID_API__ >= 24
+
 // Container for output targets
 typedef struct ACameraOutputTargets ACameraOutputTargets;
 
@@ -302,6 +304,10 @@
  */
 void ACaptureRequest_free(ACaptureRequest* request) __INTRODUCED_IN(24);
 
+#endif /* __ANDROID_API__ >= 24 */
+
+#if __ANDROID_API__ >= 28
+
 /**
  * Associate an arbitrary user context pointer to the {@link ACaptureRequest}
  *
@@ -350,6 +356,8 @@
  */
 ACaptureRequest* ACaptureRequest_copy(const ACaptureRequest* src) __INTRODUCED_IN(28);
 
+#endif /* __ANDROID_API__ >= 28 */
+
 __END_DECLS
 
 #endif /* _NDK_CAPTURE_REQUEST_H */
diff --git a/media/ndk/include/media/NdkImage.h b/media/ndk/include/media/NdkImage.h
index 38e12e3..f936118 100644
--- a/media/ndk/include/media/NdkImage.h
+++ b/media/ndk/include/media/NdkImage.h
@@ -36,13 +36,12 @@
 #ifndef _NDK_IMAGE_H
 #define _NDK_IMAGE_H
 
+#include <stdint.h>
 #include <sys/cdefs.h>
 
 #include "NdkMediaError.h"
 
-#if __ANDROID_API__ >= 26
 #include <android/hardware_buffer.h>
-#endif /* __ANDROID_API__ >= 26 */
 
 __BEGIN_DECLS
 
@@ -516,6 +515,8 @@
     int32_t bottom;
 } AImageCropRect;
 
+#if __ANDROID_API__ >= 24
+
 /**
  * Return the image back the the system and delete the AImage object from memory.
  *
@@ -712,6 +713,10 @@
         const AImage* image, int planeIdx,
         /*out*/uint8_t** data, /*out*/int* dataLength) __INTRODUCED_IN(24);
 
+#endif /* __ANDROID_API__ >= 24 */
+
+#if __ANDROID_API__ >= 26
+
 /**
  * Return the image back the the system and delete the AImage object from memory asynchronously.
  *
@@ -756,6 +761,8 @@
  */
 media_status_t AImage_getHardwareBuffer(const AImage* image, /*out*/AHardwareBuffer** buffer) __INTRODUCED_IN(26);
 
+#endif /* __ANDROID_API__ >= 26 */
+
 __END_DECLS
 
 #endif //_NDK_IMAGE_H
diff --git a/media/ndk/include/media/NdkImageReader.h b/media/ndk/include/media/NdkImageReader.h
index eb1a44a..68de176 100644
--- a/media/ndk/include/media/NdkImageReader.h
+++ b/media/ndk/include/media/NdkImageReader.h
@@ -50,6 +50,8 @@
  */
 typedef struct AImageReader AImageReader;
 
+#if __ANDROID_API__ >= 24
+
 /**
  * Create a new reader for images of the desired size and format.
  *
@@ -296,6 +298,10 @@
 media_status_t AImageReader_setImageListener(
         AImageReader* reader, AImageReader_ImageListener* listener) __INTRODUCED_IN(24);
 
+#endif /* __ANDROID_API__ >= 24 */
+
+#if __ANDROID_API__ >= 26
+
 /**
  * AImageReader constructor similar to {@link AImageReader_new} that takes an additional parameter
  * for the consumer usage. All other parameters and the return values are identical to those passed
@@ -455,6 +461,8 @@
 media_status_t AImageReader_setBufferRemovedListener(
         AImageReader* reader, AImageReader_BufferRemovedListener* listener) __INTRODUCED_IN(26);
 
+#endif /* __ANDROID_API__ >= 26 */
+
 __END_DECLS
 
 #endif //_NDK_IMAGE_READER_H
diff --git a/media/ndk/include/media/NdkMediaCodec.h b/media/ndk/include/media/NdkMediaCodec.h
index b329b39..9dc120d 100644
--- a/media/ndk/include/media/NdkMediaCodec.h
+++ b/media/ndk/include/media/NdkMediaCodec.h
@@ -121,6 +121,8 @@
       AMediaCodecOnAsyncError           onAsyncError;
 };
 
+#if __ANDROID_API__ >= 21
+
 /**
  * Create codec by name. Use this if you know the exact codec you want to use.
  * When configuring, you will need to specify whether to use the codec as an
@@ -274,6 +276,8 @@
 media_status_t AMediaCodec_releaseOutputBufferAtTime(
         AMediaCodec *mData, size_t idx, int64_t timestampNs) __INTRODUCED_IN(21);
 
+#if __ANDROID_API__ >= 26
+
 /**
  * Creates a Surface that can be used as the input to encoder, in place of input buffers
  *
@@ -344,6 +348,10 @@
  */
 media_status_t AMediaCodec_signalEndOfInputStream(AMediaCodec *mData) __INTRODUCED_IN(26);
 
+#endif /* __ANDROID_API__ >= 26 */
+
+#if __ANDROID_API__ >= 28
+
 /**
  * Get the component name. If the codec was created by createDecoderByType
  * or createEncoderByType, what component is chosen is not known beforehand.
@@ -405,6 +413,8 @@
  */
 bool AMediaCodecActionCode_isTransient(int32_t actionCode) __INTRODUCED_IN(28);
 
+#endif /* __ANDROID_API__ >= 28 */
+
 typedef enum {
     AMEDIACODECRYPTOINFO_MODE_CLEAR = 0,
     AMEDIACODECRYPTOINFO_MODE_AES_CTR = 1,
@@ -483,6 +493,8 @@
  */
 media_status_t AMediaCodecCryptoInfo_getEncryptedBytes(AMediaCodecCryptoInfo*, size_t *dst) __INTRODUCED_IN(21);
 
+#endif /* __ANDROID_API__ >= 21 */
+
 __END_DECLS
 
 #endif //_NDK_MEDIA_CODEC_H
diff --git a/media/ndk/include/media/NdkMediaCrypto.h b/media/ndk/include/media/NdkMediaCrypto.h
index b673adc..bcdf9a0 100644
--- a/media/ndk/include/media/NdkMediaCrypto.h
+++ b/media/ndk/include/media/NdkMediaCrypto.h
@@ -47,6 +47,8 @@
 
 typedef uint8_t AMediaUUID[16];
 
+#if __ANDROID_API__ >= 21
+
 bool AMediaCrypto_isCryptoSchemeSupported(const AMediaUUID uuid) __INTRODUCED_IN(21);
 
 bool AMediaCrypto_requiresSecureDecoderComponent(const char *mime) __INTRODUCED_IN(21);
@@ -55,6 +57,8 @@
 
 void AMediaCrypto_delete(AMediaCrypto* crypto) __INTRODUCED_IN(21);
 
+#endif /* __ANDROID_API__ >= 21 */
+
 __END_DECLS
 
 #endif // _NDK_MEDIA_CRYPTO_H
diff --git a/media/ndk/include/media/NdkMediaDataSource.h b/media/ndk/include/media/NdkMediaDataSource.h
index 3a4373c..ea5ba0c 100644
--- a/media/ndk/include/media/NdkMediaDataSource.h
+++ b/media/ndk/include/media/NdkMediaDataSource.h
@@ -38,6 +38,8 @@
 struct AMediaDataSource;
 typedef struct AMediaDataSource AMediaDataSource;
 
+#if __ANDROID_API__ >= 28
+
 /*
  * AMediaDataSource's callbacks will be invoked on an implementation-defined thread
  * or thread pool. No guarantees are provided about which thread(s) will be used for
@@ -133,6 +135,8 @@
         AMediaDataSource*,
         AMediaDataSourceClose) __INTRODUCED_IN(28);
 
+#endif  /*__ANDROID_API__ >= 28 */
+
 __END_DECLS
 
 #endif // _NDK_MEDIA_DATASOURCE_H
diff --git a/media/ndk/include/media/NdkMediaDrm.h b/media/ndk/include/media/NdkMediaDrm.h
index 24c0d6d..0209681 100644
--- a/media/ndk/include/media/NdkMediaDrm.h
+++ b/media/ndk/include/media/NdkMediaDrm.h
@@ -87,6 +87,8 @@
 typedef void (*AMediaDrmEventListener)(AMediaDrm *, const AMediaDrmSessionId *sessionId,
         AMediaDrmEventType eventType, int extra, const uint8_t *data, size_t dataSize);
 
+#if __ANDROID_API__ >= 21
+
 /**
  * Query if the given scheme identified by its UUID is supported on this device, and
  * whether the drm plugin is able to handle the media container format specified by mimeType.
@@ -459,6 +461,8 @@
         const char *macAlgorithm, uint8_t *keyId, const uint8_t *message, size_t messageSize,
         const uint8_t *signature, size_t signatureSize) __INTRODUCED_IN(21);
 
+#endif /* __ANDROID_API__ >= 21 */
+
 __END_DECLS
 
 #endif //_NDK_MEDIA_DRM_H
diff --git a/media/ndk/include/media/NdkMediaExtractor.h b/media/ndk/include/media/NdkMediaExtractor.h
index 9f60891..6a1796f 100644
--- a/media/ndk/include/media/NdkMediaExtractor.h
+++ b/media/ndk/include/media/NdkMediaExtractor.h
@@ -49,6 +49,8 @@
 struct AMediaExtractor;
 typedef struct AMediaExtractor AMediaExtractor;
 
+#if __ANDROID_API__ >= 21
+
 /**
  * Create new media extractor
  */
@@ -72,12 +74,16 @@
         const char *location) __INTRODUCED_IN(21);
         // TODO support headers
 
+#if __ANDROID_API__ >= 28
+
 /**
  * Set the custom data source implementation from which the extractor will read.
  */
 media_status_t AMediaExtractor_setDataSourceCustom(AMediaExtractor*,
         AMediaDataSource *src) __INTRODUCED_IN(28);
 
+#endif /* __ANDROID_API__ >= 28 */
+
 /**
  * Return the number of tracks in the previously specified media file
  */
@@ -173,6 +179,8 @@
     AMEDIAEXTRACTOR_SAMPLE_FLAG_ENCRYPTED = 2,
 };
 
+#if __ANDROID_API__ >= 28
+
 /**
  * Returns the format of the extractor. The caller must free the returned format
  * using AMediaFormat_delete(format).
@@ -219,6 +227,10 @@
 media_status_t AMediaExtractor_getSampleFormat(AMediaExtractor *ex,
         AMediaFormat *fmt) __INTRODUCED_IN(28);
 
+#endif /* __ANDROID_API__ >= 28 */
+
+#endif /* __ANDROID_API__ >= 21 */
+
 __END_DECLS
 
 #endif // _NDK_MEDIA_EXTRACTOR_H
diff --git a/media/ndk/include/media/NdkMediaFormat.h b/media/ndk/include/media/NdkMediaFormat.h
index 8f37f7b..5f7804d 100644
--- a/media/ndk/include/media/NdkMediaFormat.h
+++ b/media/ndk/include/media/NdkMediaFormat.h
@@ -46,6 +46,8 @@
 struct AMediaFormat;
 typedef struct AMediaFormat AMediaFormat;
 
+#if __ANDROID_API__ >= 21
+
 AMediaFormat *AMediaFormat_new() __INTRODUCED_IN(21);
 media_status_t AMediaFormat_delete(AMediaFormat*) __INTRODUCED_IN(21);
 
@@ -155,6 +157,9 @@
 extern const char* AMEDIAFORMAT_KEY_TRACK_INDEX __INTRODUCED_IN(28);
 extern const char* AMEDIAFORMAT_KEY_WIDTH __INTRODUCED_IN(21);
 
+#endif /* __ANDROID_API__ >= 21 */
+
+#if __ANDROID_API__ >= 28
 bool AMediaFormat_getDouble(AMediaFormat*, const char *name, double *out) __INTRODUCED_IN(28);
 bool AMediaFormat_getRect(AMediaFormat*, const char *name,
         int32_t *left, int32_t *top, int32_t *right, int32_t *bottom) __INTRODUCED_IN(28);
@@ -163,6 +168,7 @@
 void AMediaFormat_setSize(AMediaFormat*, const char* name, size_t value) __INTRODUCED_IN(28);
 void AMediaFormat_setRect(AMediaFormat*, const char* name,
         int32_t left, int32_t top, int32_t right, int32_t bottom) __INTRODUCED_IN(28);
+#endif /* __ANDROID_API__ >= 28 */
 
 __END_DECLS
 
diff --git a/media/ndk/include/media/NdkMediaMuxer.h b/media/ndk/include/media/NdkMediaMuxer.h
index 75c70ed..7393867 100644
--- a/media/ndk/include/media/NdkMediaMuxer.h
+++ b/media/ndk/include/media/NdkMediaMuxer.h
@@ -53,6 +53,8 @@
     AMEDIAMUXER_OUTPUT_FORMAT_WEBM   = 1,
 } OutputFormat;
 
+#if __ANDROID_API__ >= 21
+
 /**
  * Create new media muxer
  */
@@ -121,6 +123,8 @@
         size_t trackIdx, const uint8_t *data,
         const AMediaCodecBufferInfo *info) __INTRODUCED_IN(21);
 
+#endif /* __ANDROID_API__ >= 21 */
+
 __END_DECLS
 
 #endif // _NDK_MEDIA_MUXER_H