[libcamera-devel] [PATCH v1 08/10] pipeline: raspberrypi: Allow pipeline handler to always use the newest frame

[David Plowman]

Hi Naush

Thanks for the patch!

On Fri, 14 Oct 2022 at 14:19, Naushir Patuck via libcamera-devel
<libcamera-devel at lists.libcamera.org> wrote:
>
> 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 at raspberrypi.com>
> ---
>  .../pipeline/raspberrypi/data/default.json    |  7 ++++++-
>  .../pipeline/raspberrypi/raspberrypi.cpp      | 19 +++++++++++++++++++
>  2 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/src/libcamera/pipeline/raspberrypi/data/default.json b/src/libcamera/pipeline/raspberrypi/data/default.json
> index 707414bcc5c5..f900ca824523 100644
> --- a/src/libcamera/pipeline/raspberrypi/data/default.json
> +++ b/src/libcamera/pipeline/raspberrypi/data/default.json
> @@ -18,6 +18,11 @@
>                  "num_output0_buffers": 1,
>
>                  # 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 heavey CPU loading.

s/heavey/heavy/    (sorry!)

Reviewed-by: David Plowman <david.plowman at raspberrypi.com>

Thanks!
David

> +                "return_newest_frames": false
>          }
>  }
> diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> index 135948d82f41..d9bea35c88a3 100644
> --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> @@ -301,6 +301,7 @@ public:
>                 unsigned int minTotalUnicamBuffers;
>                 unsigned int numOutput0Buffers;
>                 bool disableStartupFrameDrops;
> +               bool returnNewestFrames;
>         };
>
>         Config config_;
> @@ -1432,6 +1433,7 @@ int PipelineHandlerRPi::configurePipelineHandler(RPiCameraData *data)
>                 .minTotalUnicamBuffers = 4,
>                 .numOutput0Buffers = 1,
>                 .disableStartupFrameDrops = false,
> +               .returnNewestFrames = false,
>         };
>
>         char const *configFromEnv = utils::secure_getenv("LIBCAMERA_RPI_CONFIG_FILE");
> @@ -1468,6 +1470,8 @@ int PipelineHandlerRPi::configurePipelineHandler(RPiCameraData *data)
>                 phConfig["num_output0_buffers"].get<unsigned int>(config.numOutput0Buffers);
>         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 || config.minTotalUnicamBuffers < 1) {
>                 LOG(RPI, Error) << "Invalid Unicam buffer configuration used!";
> @@ -2320,6 +2324,21 @@ 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
> --
> 2.25.1
>