[libcamera-devel] [PATCH v3 08/10] android: camera_buffer: Add method to get the JPEG blob size

[Jacopo Mondi]

To maintain compatibility with platforms that do not provide a memory
backend implementation add a method to be return the size of the buffer
used for JPEG encoding capped to a maximum size.

Platforms that implement a memory backend will always calculate the
correct buffer size.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/android/camera_buffer.h              |  2 ++
 src/android/jpeg/post_processor_jpeg.cpp | 12 ++++++++++--
 src/android/mm/generic_camera_buffer.cpp | 14 ++++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/android/camera_buffer.h b/src/android/camera_buffer.h
index 2311cdaf96b2..342aac6d3f14 100644
--- a/src/android/camera_buffer.h
+++ b/src/android/camera_buffer.h
@@ -26,6 +26,8 @@ public:
 
 	libcamera::Span<const uint8_t> plane(unsigned int plane) const;
 	libcamera::Span<uint8_t> plane(unsigned int plane);
+
+	size_t jpegBlobSize(size_t maxJpegBlobSize);
 };
 
 #endif /* __ANDROID_CAMERA_BUFFER_H__ */
diff --git a/src/android/jpeg/post_processor_jpeg.cpp b/src/android/jpeg/post_processor_jpeg.cpp
index 83244ce6769e..65ab6b196ad1 100644
--- a/src/android/jpeg/post_processor_jpeg.cpp
+++ b/src/android/jpeg/post_processor_jpeg.cpp
@@ -182,8 +182,16 @@ int PostProcessorJpeg::process(const FrameBuffer &source,
 	}
 
 	/* Fill in the JPEG blob header. */
-	uint8_t *resultPtr = destination->plane(0).data()
-			   + destination->plane(0).size()
+	/*
+	 * \todo For backward compatibility reasons with the android_generic
+	 * memory backend, continue using the maxJpegBufferSize in case the
+	 * computed buffer size is larger. This can be dropped once all
+	 * supported platforms will have a working memory backend that
+	 * returns the correct buffer size.
+	 */
+	size_t blobSize = std::min<unsigned int>(cameraDevice_->maxJpegBufferSize(),
+						 destination->plane(0).size());
+	uint8_t *resultPtr = destination->plane(0).data() + blobSize
 			   - sizeof(struct camera3_jpeg_blob);
 	auto *blob = reinterpret_cast<struct camera3_jpeg_blob *>(resultPtr);
 	blob->jpeg_blob_id = CAMERA3_JPEG_BLOB_ID;
diff --git a/src/android/mm/generic_camera_buffer.cpp b/src/android/mm/generic_camera_buffer.cpp
index 45a83c351266..5637b3f415eb 100644
--- a/src/android/mm/generic_camera_buffer.cpp
+++ b/src/android/mm/generic_camera_buffer.cpp
@@ -27,6 +27,8 @@ public:
 	unsigned int numPlanes() const;
 
 	Span<uint8_t> plane(unsigned int plane);
+
+	size_t jpegBlobSize(size_t maxJpegBlobSize);
 };
 
 CameraBuffer::Private::Private(CameraBuffer *cameraBuffer,
@@ -77,6 +79,12 @@ Span<uint8_t> CameraBuffer::Private::plane(unsigned int plane)
 	return maps_[plane];
 }
 
+size_t CameraBuffer::Private::jpegBlobSize(size_t maxJpegBlobSize)
+{
+	return std::min<unsigned int>(plane(0).size(),
+				      maxJpegBlobSize);
+}
+
 CameraBuffer::CameraBuffer(buffer_handle_t camera3Buffer, int flags)
 	: Extensible(new Private(this, camera3Buffer, flags))
 {
@@ -109,3 +117,9 @@ Span<uint8_t> CameraBuffer::plane(unsigned int plane)
 	Private *const d = LIBCAMERA_D_PTR();
 	return d->plane(plane);
 }
+
+size_t CameraBuffer::jpegBlobSize(size_t maxJpegBlobSize)
+{
+	Private *const d = LIBCAMERA_D_PTR();
+	return d->jpegBlobSize(maxJpegBlobSize);
+}
-- 
2.30.0