1 files changed, 85 insertions, 1 deletions

diff --git a/src/android/camera_stream.h b/src/android/camera_stream.h
index 0de6b6fc..e5427686 100644
--- a/src/android/camera_stream.h
+++ b/src/android/camera_stream.h
@@ -17,17 +17,101 @@ class Encoder;
 class CameraStream
 {
 public:
+	/*
+	 * Enumeration of CameraStream types.
+	 *
+	 * A camera stream associates an Android stream to a libcamera stream.
+	 * This enumeration describes how the two streams are associated and how
+	 * and where data produced from libcamera are delivered to the
+	 * Android framework.
+	 *
+	 * Direct:
+	 *
+	 * The Android stream is directly mapped onto a libcamera stream: frames
+	 * are delivered by the library directly in the memory location
+	 * specified by the Android stream (buffer_handle_t->data) and provided
+	 * to the framework as they are. The Android stream characteristics are
+	 * directly translated to the libcamera stream configuration.
+	 *
+	 * +-----+                +-----+
+	 * |  A  |                |  L  |
+	 * +-----+                +-----+
+	 *    |                      |
+	 *    V                      V
+	 * +-----+                +------+
+	 * |  B  |<---------------|  FB  |
+	 * +-----+                +------+
+	 *
+	 *
+	 * Internal:
+	 *
+	 * Data for the Android stream is produced by processing a libcamera
+	 * stream created by the HAL for that purpose. The libcamera stream
+	 * needs to be supplied with intermediate buffers where the library
+	 * delivers frames to be processed and then provided to the framework.
+	 * The libcamera stream configuration is not a direct translation of the
+	 * Android stream characteristics, but it describes the format and size
+	 * required for the processing procedure to produce frames in the
+	 * Android required format.
+	 *
+	 * +-----+                +-----+
+	 * |  A  |                |  L  |
+	 * +-----+                +-----+
+	 *    |                      |
+	 *    V                      V
+	 * +-----+                +------+
+	 * |  B  |                |  FB  |
+	 * +-----+                +------+
+	 *   ^                       |
+	 *   |-------Processing------|
+	 *
+	 *
+	 * Mapped:
+	 *
+	 * Data for the Android stream is produced by processing a libcamera
+	 * stream associated with another CameraStream. Mapped camera streams do
+	 * not need any memory to be reserved for them as they process data
+	 * produced by libcamera for a different stream whose format and size
+	 * are compatible with the processing procedure requirements to produce
+	 * frames in the Android required format.
+	 *
+	 * +-----+      +-----+          +-----+
+	 * |  A  |      |  A' |          |  L  |
+	 * +-----+      +-----+          +-----+
+	 *    |            |                |
+	 *    V            V                V
+	 * +-----+      +-----+          +------+
+	 * |  B  |      |  B' |<---------|  FB  |
+	 * +-----+      +-----+          +------+
+	 *   ^              |
+	 *   |--Processing--|
+	 *
+	 *
+	 * --------------------------------------------------------------------
+	 * A  = Android stream
+	 * L  = libcamera stream
+	 * B  = memory buffer
+	 * FB = libcamera FrameBuffer
+	 * "Processing" = Frame processing procedure (Encoding, scaling etc)
+	 */
+	enum class Type {
+		Direct,
+		Internal,
+		Mapped,
+	};
 	CameraStream(libcamera::PixelFormat format, libcamera::Size size,
-		     unsigned int index, Encoder *encoder = nullptr);
+		     Type type, unsigned int index, Encoder *encoder = nullptr);
 
 	const libcamera::PixelFormat &format() const { return format_; }
 	const libcamera::Size &size() const { return size_; }
+	Type type() const { return type_; }
 	unsigned int index() const { return index_; }
 	Encoder *encoder() const { return encoder_.get(); }
 
 private:
 	libcamera::PixelFormat format_;
 	libcamera::Size size_;
+	Type type_;
 	/*
 	 * The index of the libcamera StreamConfiguration as added during
 	 * configureStreams(). A single libcamera Stream may be used to deliver