[libcamera-devel,v4,11/12] pipeline: raspberrypi: Allow pipeline handler to always use the newest frame
diff mbox series

Message ID 20221209090050.19441-12-naush@raspberrypi.com
State Superseded
Headers show
Series
  • Raspberry Pi: Platform configuration and buffer allocation improvements
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Commit Message

Naushir Patuck Dec. 9, 2022, 9 a.m. UTC 
Add a pipeline config parameter "return_newest_frames" to always use the
most recently captured Unicam frame when processing a request. This effectively
stops the pipeline handler from queuing Unicam buffers and processing requests
using the buffer at the front of the queue.

Note that setting this parameter might incur unnecessary frame drops during
times of high transient CPU loads where the application might not be able to
provide requests quick enough.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
---
 .../pipeline/raspberrypi/data/example.yaml    |  7 +++++-
 .../pipeline/raspberrypi/raspberrypi.cpp      | 23 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

Patch
diff mbox series 

diff --git a/src/libcamera/pipeline/raspberrypi/data/example.yaml b/src/libcamera/pipeline/raspberrypi/data/example.yaml
index 421f30e62aa3..04a117f38ada 100644
--- a/src/libcamera/pipeline/raspberrypi/data/example.yaml
+++ b/src/libcamera/pipeline/raspberrypi/data/example.yaml
@@ -19,6 +19,11 @@ 
 
                 # Override any request from the IPA to drop a number of startup
                 # frames.
-                "disable_startup_frame_drops": false
+                "disable_startup_frame_drops": false,
+
+                # Always process a pending request with the last captured sensor
+                # frame.  Note that this might lead to avoidable frame drops
+                # during periods of transient heavy CPU loading.
+                "return_newest_frames": false
         }
 }
diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
index 4f15bcf0052a..68c70cc19995 100644
--- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
+++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
@@ -313,6 +313,11 @@  public:
 		 * frames.
 		 */
 		bool disableStartupFrameDrops;
+		/*
+		 * Always process a pending request with the last captured sensor
+		 * frame.
+		 */
+		bool returnNewestFrames;
 	};
 
 	Config config_;
@@ -1712,6 +1717,7 @@  int RPiCameraData::configurePipeline()
 		.minUnicamBuffers = 2,
 		.minTotalUnicamBuffers = 4,
 		.disableStartupFrameDrops = false,
+		.returnNewestFrames = false,
 	};
 
 	char const *configFromEnv = utils::secure_getenv("LIBCAMERA_RPI_CONFIG_FILE");
@@ -1747,6 +1753,8 @@  int RPiCameraData::configurePipeline()
 		phConfig["min_total_unicam_buffers"].get<unsigned int>(config_.minTotalUnicamBuffers);
 	config_.disableStartupFrameDrops =
 		phConfig["disable_startup_frame_drops"].get<bool>(config_.disableStartupFrameDrops);
+	config_.returnNewestFrames =
+		phConfig["return_newest_frames"].get<bool>(config_.returnNewestFrames);
 
 	if (config_.minTotalUnicamBuffers < config_.minUnicamBuffers) {
 		LOG(RPI, Error) << "Invalid configuration: min_total_unicam_buffers must be >= min_unicam_buffers";
@@ -2326,6 +2334,21 @@  bool RPiCameraData::findMatchingBuffers(BayerFrame &bayerFrame, FrameBuffer *&em
 	if (bayerQueue_.empty())
 		return false;
 
+	/*
+	 * If the pipeline is configured to only ever return the most recently
+	 * captured frame, empty the buffer queue until a single element is
+	 * left, corresponding to the most recent buffer. Note that this will
+	 * likely result in possibly avoidable dropped frames.
+	 */
+	if (config_.returnNewestFrames && !unicam_[Unicam::Image].isExternal()) {
+		while (bayerQueue_.size() > 1) {
+			FrameBuffer *bayer = bayerQueue_.front().buffer;
+
+			unicam_[Unicam::Image].returnBuffer(bayer);
+			bayerQueue_.pop();
+		}
+	}
+
 	/*
 	 * Find the embedded data buffer with a matching timestamp to pass to
 	 * the IPA. Any embedded buffers with a timestamp lower than the