diff --git a/include/media/hardware/MetadataBufferType.h b/include/media/hardware/MetadataBufferType.h
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+++ b/include/media/hardware/MetadataBufferType.h
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+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef METADATA_BUFFER_TYPE_H
+#define METADATA_BUFFER_TYPE_H
+
+#ifdef __cplusplus
+extern "C" {
+namespace android {
+#endif
+
+/*
+ * MetadataBufferType defines the type of the metadata buffers that
+ * can be passed to video encoder component for encoding, via Stagefright
+ * media recording framework. To see how to work with the metadata buffers
+ * in media recording framework, please consult HardwareAPI.h
+ *
+ * The creator of metadata buffers and video encoder share common knowledge
+ * on what is actually being stored in these metadata buffers, and
+ * how the information can be used by the video encoder component
+ * to locate the actual pixel data as the source input for video
+ * encoder, plus whatever other information that is necessary. Stagefright
+ * media recording framework does not need to know anything specific about the
+ * metadata buffers, except for receving each individual metadata buffer
+ * as the source input, making a copy of the metadata buffer, and passing the
+ * copy via OpenMAX API to the video encoder component.
+ *
+ * The creator of the metadata buffers must ensure that the first
+ * 4 bytes in every metadata buffer indicates its buffer type,
+ * and the rest of the metadata buffer contains the
+ * actual metadata information. When a video encoder component receives
+ * a metadata buffer, it uses the first 4 bytes in that buffer to find
+ * out the type of the metadata buffer, and takes action appropriate
+ * to that type of metadata buffers (for instance, locate the actual
+ * pixel data input and then encoding the input data to produce a
+ * compressed output buffer).
+ *
+ * The following shows the layout of a metadata buffer,
+ * where buffer type is a 4-byte field of MetadataBufferType,
+ * and the payload is the metadata information.
+ *
+ * --------------------------------------------------------------
+ * |  buffer type  |          payload                           |
+ * --------------------------------------------------------------
+ *
+ */
+typedef enum {
+
+    /*
+     * kMetadataBufferTypeCameraSource is used to indicate that
+     * the source of the metadata buffer is the camera component.
+     */
+    kMetadataBufferTypeCameraSource  = 0,
+
+    /*
+     * kMetadataBufferTypeGrallocSource is used to indicate that
+     * the payload of the metadata buffers can be interpreted as
+     * a buffer_handle_t.
+     * So in this case,the metadata that the encoder receives
+     * will have a byte stream that consists of two parts:
+     * 1. First, there is an integer indicating that it is a GRAlloc
+     * source (kMetadataBufferTypeGrallocSource)
+     * 2. This is followed by the buffer_handle_t that is a handle to the
+     * GRalloc buffer. The encoder needs to interpret this GRalloc handle
+     * and encode the frames.
+     * --------------------------------------------------------------
+     * |  kMetadataBufferTypeGrallocSource | sizeof(buffer_handle_t) |
+     * --------------------------------------------------------------
+     */
+    kMetadataBufferTypeGrallocSource = 1,
+
+    // Add more here...
+
+} MetadataBufferType;
+
+#ifdef __cplusplus
+}  // namespace android
+}
+#endif
+
+#endif  // METADATA_BUFFER_TYPE_H