[libcamera-devel] [PATCH v1 09/10] pipeline: raspberrypi: Add minimal memory usage config file

[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 platform configuration file that allocates the least amount of frame
> buffer memory possible. This configuration does come with the following
> compromises:
>
> - Startup frame drops are disabled, so the first few frames will not have
> fully converged AE/AWB/ALSC applied.
>
> - Applications must provide ISP Output0 and Unicam Image (if a RAW stream is
> configured) buffers in requests.
>
> - Only 1 Unicam Image buffer will be allocated if a RAW stream is not
> configured, causing the framerate to be effectively halved.

I wonder how useful this really is with a limitation like this? On the
other hand, I could imagine it might be more useful in conjunction
with, for example, stills capture rather than preview or video. Making
it camera mode (or better, use-case) specific sounds like a whole new
can of worms. Perhaps better not go there right now!

Is there any benefit in a minimal-but-not-framerate-halving version?
Though we could easily end up with a plethora of configuration files
that we would really want to be testing all the time.

Anyway, I shall sit back and wait for the "I pointed my Pi Zero at
this config file so that Picamera2 would work with my
zillion-megapixel sensor" bugs  :)

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

Thanks!
David

>
> To use the configuration on the Raspberry Pi platform, invoke the application
> with the following prepended to the command line:
>
> LIBCAMERA_RPI_CONFIG_FILE=/usr/local/share/libcamera/pipeline/raspberrypi/minimal_memory.json
>
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> ---
>  .../pipeline/raspberrypi/data/meson.build     |  1 +
>  .../raspberrypi/data/minimal_mem.json         | 28 +++++++++++++++++++
>  2 files changed, 29 insertions(+)
>  create mode 100644 src/libcamera/pipeline/raspberrypi/data/minimal_mem.json
>
> diff --git a/src/libcamera/pipeline/raspberrypi/data/meson.build b/src/libcamera/pipeline/raspberrypi/data/meson.build
> index 232f8b43c5fd..0592fc53877d 100644
> --- a/src/libcamera/pipeline/raspberrypi/data/meson.build
> +++ b/src/libcamera/pipeline/raspberrypi/data/meson.build
> @@ -2,6 +2,7 @@
>
>  conf_files = files([
>      'default.json',
> +    'minimal_mem.json',
>  ])
>
>  install_data(conf_files,
> diff --git a/src/libcamera/pipeline/raspberrypi/data/minimal_mem.json b/src/libcamera/pipeline/raspberrypi/data/minimal_mem.json
> new file mode 100644
> index 000000000000..fb306aa08f94
> --- /dev/null
> +++ b/src/libcamera/pipeline/raspberrypi/data/minimal_mem.json
> @@ -0,0 +1,28 @@
> +{
> +        "version": 1.0,
> +        "target": "bcm2835",
> +
> +        "pipeline_handler":
> +        {
> +                # The minimum number of internal buffers to be allocated for Unicam.
> +                # This value must less than or equal to min_total_unicam_buffers.
> +                "min_unicam_buffers": 0,
> +
> +                # The minimum total (internal + external) buffer count used for Unicam.
> +                # The number of internal buffers allocated for Unicam is given by:
> +                # internal buffer count = max(min_unicam_buffers,
> +                #                             min_total_unicam_buffers - external buffer count)
> +                "min_total_unicam_buffers": 1,
> +
> +                # The number of internal buffers used for ISP Output0.
> +                "num_output0_buffers": 0,
> +
> +                # Override any request from the IPA to drop a number of startup frames.
> +                "disable_startup_frame_drops": true,
> +
> +                # 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.
> +                "return_newest_frames": false
> +        }
> +}
> --
> 2.25.1
>