[libcamera-devel] [PATCH] gstreamer: Provide interlace-mode as fixated caps

[Laurent Pinchart]

Hi Umang,

Thank you for the patch.

On Mon, Aug 29, 2022 at 03:32:51PM +0530, Umang Jain via libcamera-devel wrote:
> The 'interlace-mode' for libcamerasrc will always be 'progressive'.

I'm *really* crossing my fingers, hoping that you're right :-)

> Provide it via fixated caps mechanism [1]
> 
> [1] https://gstreamer.freedesktop.org/documentation/plugin-development/advanced/negotiation.html?gi-language=c#fixed-negotiation
> 
> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> ---
> Rishi, Can you please check this patch as well? I think it will closely
> co-relate with the framerate being captured in caps, as fixate
> negotitation mechanism.
> ---
>  src/gstreamer/gstlibcamerasrc.cpp | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
> index 16d70fea..24a2e33e 100644
> --- a/src/gstreamer/gstlibcamerasrc.cpp
> +++ b/src/gstreamer/gstlibcamerasrc.cpp
> @@ -800,11 +800,37 @@ gst_libcamera_src_release_pad(GstElement *element, GstPad *pad)
>  	gst_element_remove_pad(element, pad);
>  }
>  
> +static GstCaps *gst_libcamera_src_src_fixate([[maybe_unused]] GstBaseSrc *bsrc,
> +					     GstCaps *caps)
> +{
> +	GstStructure *structure;

This could be a local variable within the loop, up to you.

> +	GstCaps *fixated_caps;
> +
> +	fixated_caps = gst_caps_make_writable(caps);
> +
> +	for (guint i = 0; i < gst_caps_get_size(fixated_caps); ++i) {
> +		structure = gst_caps_get_structure(fixated_caps, i);
> +		if (gst_structure_has_field(structure, "interlace-mode"))
> +			gst_structure_fixate_field_string(structure, "interlace-mode",
> +							  "progressive");
> +		else
> +			gst_structure_set(structure, "interlace-mode", G_TYPE_STRING,
> +					  "progressive", NULL);
> +	}
> +
> +	fixated_caps = gst_caps_fixate(fixated_caps);
> +
> +	return fixated_caps;

Just

	return gst_caps_fixate(fixated_caps);

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

But I'm no expert here.

> +}
> +
>  static void
>  gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
>  {
>  	GstElementClass *element_class = GST_ELEMENT_CLASS(klass);
>  	GObjectClass *object_class = G_OBJECT_CLASS(klass);
> +	GstBaseSrcClass *gstbasesrc_class = (GstBaseSrcClass *)klass;
> +
> +	gstbasesrc_class->fixate = gst_libcamera_src_src_fixate;
>  
>  	object_class->set_property = gst_libcamera_src_set_property;
>  	object_class->get_property = gst_libcamera_src_get_property;

-- 
Regards,

Laurent Pinchart