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

[Jacopo Mondi]

Hello,

On Mon, Mar 22, 2021 at 03:31:20PM -0400, Nicolas Dufresne wrote:
> 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.

Also there are no guarantee that FrameDurations is part of the
stream's control list, so all of this i probably better wrapped in a

        if (stream_cfg.contains(controls::FrameDurations)) {
        }

>
> 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);
> >  
> >
> >
> >
> >
> >
> >
> >
>
>
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