[libcamera-devel] [PATCH 3/3] gst: utils: Add framerate to caps

[Nicolas Dufresne]

Le lundi 22 mars 2021 à 11:42 +0100, Marian Cichy a écrit :
> Access the frame duration from the controlList of the stream
> configuration and convert it to values fitting for GST_FRACTION. By
> setting the frame rate to the caps configuration, the Gstreamer pipeline
> has information about the camera frame rate, which can be potentially
> used for more efficient memory allocation or for debug purposes.
> 
> Signed-off-by: Marian Cichy <m.cichy at pengutronix.de>
> ---
>  src/gstreamer/gstlibcamera-utils.cpp | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
> index 5381dca5..fdd8b85c 100644
> --- a/src/gstreamer/gstlibcamera-utils.cpp
> +++ b/src/gstreamer/gstlibcamera-utils.cpp
> @@ -8,6 +8,7 @@
>  
> 
> 
> 
>  #include "gstlibcamera-utils.h"
>  
> >
> +#include <libcamera/control_ids.h>
>  #include <libcamera/formats.h>
>  
>  using namespace libcamera;
> @@ -128,10 +129,16 @@ gst_libcamera_stream_configuration_to_caps(const StreamConfiguration &stream_cfg
>  {
>  	GstCaps *caps = gst_caps_new_empty();
>  	GstStructure *s = bare_structure_from_format(stream_cfg.pixelFormat);
> +	int numerator;
> +	int denominator;
> +	double framerate = 1'000'000 / static_cast<double>(stream_cfg.controls.get(
> +				controls::FrameDurations)[0]);

Perhaps that would be defensive, but I'm worried duration might be 0, which
would crash here.

Can you explain the array of duration, and why we know that the first item exist
(to we don't overrun the array) and will be the selected one ?

> 
>  +	gst_util_double_to_fraction(framerate, &numerator, &denominator);
>  	gst_structure_set(s,
>  			  "width", G_TYPE_INT, stream_cfg.size.width,
>  			  "height", G_TYPE_INT, stream_cfg.size.height,
> +			  "framerate", GST_TYPE_FRACTION, numerator, denominator,

If duration is 0, this should be skipped, or set to 0/1 (which means variable
framerate in GStreamer).

>  			  nullptr);
>  	gst_caps_append_structure(caps, s);
>  
> 
> 
> 
> 
> 
> 
>