[libcamera-devel] [PATCH] gstreamer: Implement EOS handling

nicolas at ndufresne.ca nicolas at ndufresne.ca
Thu Nov 9 16:23:12 CET 2023


Le jeudi 09 novembre 2023 à 13:40 +0000, Kieran Bingham via libcamera-
devel a écrit :
> Quoting Jaslo Ziska via libcamera-devel (2023-11-09 12:51:15)
> > Hi,
> > 
> > Umang Jain <umang.jain at ideasonboard.com> writes:
> > > Hi Jalso
> > > 
> > > On 11/6/23 10:22 PM, Jaslo Ziska via libcamera-devel wrote:
> > > > ---
> > > > Hi,
> > > > 
> > > > I recently implemented basic EOS handling for the libcamerasrc 
> > > > gstreamer element.
> > > 
> > > Ah thanks, I remember we do track a bug report here:
> > > https://bugs.libcamera.org/show_bug.cgi?id=91
> > 
> > Ah yes, I remember that I stumbled upon this when I was first 
> > investigating this, I will update the bug report.
> > 
> > > > 
> > > > I basically looked at how GstBaseSrc does it and tried to do it 
> > > > similarly.
> > > > 
> > > > I have no idea whether the locking is correct or if this is 
> > > > thread safe but so far it worked without any issues for my 
> > > > purposes.
> > > > 
> > > > You can also now run the following command and receive a 
> > > > working video file:
> > > > 
> > > > gst-launch-1.0 -e libcamerasrc ! videoconvert ! x264enc ! 
> > > > h264parse ! mp4mux ! filesink location=test.mp4
> > > 
> > > Good to see that the diff is tested :-D
> > 
> > Speaking of testing, I just ran the test suite and, except for the 
> > multi_stream_test (which was skipped) the other tests succeeded.
> > 
> > > > 
> > > > Looking forward for feedback!
> > > 
> > > It looks logical and on the right track to me atleast. But there 
> > > might be other implications regarding the threading and
> > > locking mechanisms.
> > 
> > Thanks! That is what I worry about too, maybe someone can review 
> > this.
> > 
> > > > Cheers,
> > > > 
> > > > Jaslo
> > > > 
> > > >   src/gstreamer/gstlibcamerasrc.cpp | 47 
> > > >   +++++++++++++++++++++++++++++++
> > > >   1 file changed, 47 insertions(+)
> > > > 
> > > > diff --git a/src/gstreamer/gstlibcamerasrc.cpp 
> > > > b/src/gstreamer/gstlibcamerasrc.cpp
> > > > index 63d99571..a4681e1e 100644
> > > > --- a/src/gstreamer/gstlibcamerasrc.cpp
> > > > +++ b/src/gstreamer/gstlibcamerasrc.cpp
> > > > @@ -144,6 +144,9 @@ struct _GstLibcameraSrc {
> > > >      gchar *camera_name;
> > > >      controls::AfModeEnum auto_focus_mode = 
> > > >   controls::AfModeManual;
> > > > 
> > > > +    GstEvent *pending_eos;
> > > > +    int has_pending_eos;
> > > > +
> > > >      GstLibcameraSrcState *state;
> > > >      GstLibcameraAllocator *allocator;
> > > >      GstFlowCombiner *flow_combiner;
> > > > @@ -397,6 +400,21 @@ gst_libcamera_src_task_run(gpointer 
> > > > user_data)
> > > > 
> > > >      bool doResume = false;
> > > > 
> > > > +    if (g_atomic_int_get(&self->has_pending_eos)) {
> > > > +            g_atomic_int_set(&self->has_pending_eos, FALSE);
> > > > +
> > > > +            GST_OBJECT_LOCK(self);
> > > > +            GstEvent *event = self->pending_eos;
> > > > +            self->pending_eos = NULL;
> > > > +            GST_OBJECT_UNLOCK(self);
> > > > +
> > > > +            for (GstPad *srcpad : state->srcpads_)
> > > > +                    gst_pad_push_event(srcpad, gst_event_ref(event));
> > > > +            gst_event_unref(event);
> > > > +
> > > > +            return;
> > > > +    }
> > > > +
> > > >      /*
> > > >       * Create and queue one request. If no buffers are 
> > > >   available the
> > > >       * function returns -ENOBUFS, which we ignore here as 
> > > >   that's not a
> > > > @@ -747,6 +765,32 @@ gst_libcamera_src_change_state(GstElement 
> > > > *element, GstStateChange transition)
> > > >      return ret;
> > > >   }
> > > > 
> > > > +static gboolean
> > > > +gst_libcamera_src_send_event(GstElement *element, GstEvent 
> > > > *event)
> > > > +{
> > > > +    GstLibcameraSrc *self = GST_LIBCAMERA_SRC(element);
> > > > +    gboolean ret = FALSE;
> > > > +
> > > > +    switch (GST_EVENT_TYPE(event)) {
> > > > +    case GST_EVENT_EOS: {
> > > > +            GST_OBJECT_LOCK(self);
> > > > +            g_atomic_int_set(&self->has_pending_eos, TRUE);
> > > > +            if (self->pending_eos)
> > > > +                    gst_event_unref(self->pending_eos);
> > > > +            self->pending_eos = event;
> > > > +            GST_OBJECT_UNLOCK(self);
> > > > +
> > > > +            ret = TRUE;
> > > > +            break;
> > > > +    }
> > > > +    default:
> > > > +            gst_event_unref(event);
> > > > +            break;
> > > > +    }
> > > > +
> > > > +    return ret;
> > > > +}
> > > > +
> > > >   static void
> > > >   gst_libcamera_src_finalize(GObject *object)
> > > >   {
> > > > @@ -779,6 +823,8 @@ gst_libcamera_src_init(GstLibcameraSrc 
> > > > *self)
> > > >      state->srcpads_.push_back(gst_pad_new_from_template(templ, 
> > > >   "src"));
> > > >      gst_element_add_pad(GST_ELEMENT(self), 
> > > >   state->srcpads_.back());
> > > > 
> > > > +    GST_OBJECT_FLAG_SET(self, GST_ELEMENT_FLAG_SOURCE);
> > > > +
> > > 
> > > I always thought libcamerasrc was inheriting from GstBaseSrc, 
> > > but in fact it's not.
> > > So, setting the GST_ELEMENT_FLAG_SOURCE makes sense here.
> > 
> > This flag is actually required to receive the eos signal when it 
> > is send to the pipeline bin and not the element directly. Took me 
> > a while to figure out.
> > 
> > > Apart from a missing commit mesasge, the patch looks good to me. 
> > > I'll put this on my radar soon for testing it
> > > rigorously.
> > 
> > Oh yeah, a commit message would indeed be nice, completely forgot 
> > that, thanks :)
> 
> Can you also add/clarify /how/ the EOS event is being sent in the commit
> message please?
> 
> Is this issue occuring when you run the pipeline and press ctrl-c for
> instance? or is there some other detail?

This patch covers cases where the application decides to stop the
pipeline by sending it an EOS. To CTRL+C combined with -e option of
gst-launch-1.0 is a good example.

This patch does not cover (and this can be done later/seperatly):

  libcamerasrc ! identity eos-after=10 ! fakesink

Which is the case when downstream decides to stop. This case is a
little more complex for multi-pad elements and is actually nice to
tackle separately (its also more niche).

Nicolas

> 
> --
> Kieran
> 
> 
> > 
> > > >      /* C-style friend. */
> > > >      state->src_ = self;
> > > >      self->state = state;
> > > > @@ -844,6 +890,7 @@ 
> > > > gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
> > > >      element_class->request_new_pad = 
> > > >   gst_libcamera_src_request_new_pad;
> > > >      element_class->release_pad = 
> > > >   gst_libcamera_src_release_pad;
> > > >      element_class->change_state = 
> > > >   gst_libcamera_src_change_state;
> > > > +    element_class->send_event = gst_libcamera_src_send_event;
> > > > 
> > > >      gst_element_class_set_metadata(element_class,
> > > >                                     "libcamera Source", "Source/Video",
> > > > --
> > > > 2.42.1
> > 
> > Regards,
> > 
> > Jaslo



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