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gstreamer: Implement renegotiation

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This commit implements renegotiation of the camera configuration and
source pad caps. A renegotiation can happen when a downstream element
decides to change caps or the pipeline is dynamically changed.

To handle a renegotiation the GST_FLOW_NOT_NEGOTIATED return value has
to be handled in GstLibcameraSrcState::processRequest(). Otherwise the
default would be to print an error and stop streaming.

To archive this in a clean way the if statement is altered into a switch
statement which now also has a case for GST_FLOW_NOT_NEGOTIATED. In the
case of GST_FLOW_NOT_NEGOTIATED every source pad is checked for the
reconfiguration flag with gst_pad_needs_reconfigure() which does not
clear this flag. If at least one pad requested a reconfiguration the
function returns without an error and the renegotiation will happen
later in the running task. If no pad requested a reconfiguration then
the function will return with an error.

In gst_libcamera_src_task_run() the source pads are checked for the
reconfigure flag by calling gst_pad_check_reconfigure() and if one pad
returns true and the caps are not sufficient anymore then the
negotiation is triggered. It is fine to trigger the negotiation after
only a single pad returns true for gst_pad_check_reconfigure() because
the reconfigure flags are cleared in the gst_libcamera_src_negotiate()
function.

If any pad requested a reconfiguration the following will happen:
1. The camera is stopped because changing the configuration may not
   happen while running.
2. The completedRequests queue will be cleared by calling
   GstLibcameraSrcState::clearRequests() because the completed buffers
   have the wrong configuration.
3. The new caps are negotiated by calling gst_libcamera_src_negotiate().
   When the negotiation fails streaming will stop.
4. The camera is started again.

Signed-off-by: Jaslo Ziska <jaslo@ziska.de>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Tested-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
This commit is contained in:
Jaslo Ziska 2023-11-30 16:43:10 +01:00 • committed by Laurent Pinchart
parent bf231ead1c
commit b06ebdedba
1 changed files with 66 additions and 11 deletions
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67
src/gstreamer/gstlibcamerasrc.cpp
View file

@ -11,7 +11,6 @@
* - Implement GstElement::send_event
* + Allowing application to use FLUSH/FLUSH_STOP
* + Prevent the main thread from accessing streaming thread
* - Implement renegotiation (even if slow)
* - Implement GstElement::request-new-pad (multi stream)
* + Evaluate if a single streaming thread is fine
* - Add application driven request (snapshot)
@ -302,18 +301,46 @@ int GstLibcameraSrcState::processRequest()
srcpad, ret);
}
if (ret != GST_FLOW_OK) {
if (ret == GST_FLOW_EOS) {
switch (ret) {
case GST_FLOW_OK:
break;
case GST_FLOW_NOT_NEGOTIATED: {
bool reconfigure = false;
for (GstPad *srcpad : srcpads_) {
if (gst_pad_needs_reconfigure(srcpad)) {
reconfigure = true;
break;
}
}
/* If no pads need a reconfiguration something went wrong. */
if (!reconfigure)
err = -EPIPE;
break;
}
case GST_FLOW_EOS: {
g_autoptr(GstEvent) eos = gst_event_new_eos();
guint32 seqnum = gst_util_seqnum_next();
gst_event_set_seqnum(eos, seqnum);
for (GstPad *srcpad : srcpads_)
gst_pad_push_event(srcpad, gst_event_ref(eos));
} else if (ret != GST_FLOW_FLUSHING) {
GST_ELEMENT_FLOW_ERROR(src_, ret);
err = -EPIPE;
break;
}
return -EPIPE;
case GST_FLOW_FLUSHING:
err = -EPIPE;
break;
default:
GST_ELEMENT_FLOW_ERROR(src_, ret);
err = -EPIPE;
break;
}
return err;
@ -462,6 +489,9 @@ gst_libcamera_src_negotiate(GstLibcameraSrc *self)
G_CALLBACK(gst_task_resume), self->task);
gst_libcamera_pad_set_pool(srcpad, pool);
/* Clear all reconfigure flags. */
gst_pad_check_reconfigure(srcpad);
}
return true;
@ -495,6 +525,31 @@ gst_libcamera_src_task_run(gpointer user_data)
return;
}
/* Check if a srcpad requested a renegotiation. */
bool reconfigure = false;
for (GstPad *srcpad : state->srcpads_) {
if (gst_pad_check_reconfigure(srcpad)) {
/* Check if the caps even need changing. */
g_autoptr(GstCaps) caps = gst_pad_get_current_caps(srcpad);
if (!gst_pad_peer_query_accept_caps(srcpad, caps)) {
reconfigure = true;
break;
}
}
}
if (reconfigure) {
state->cam_->stop();
state->clearRequests();
if (!gst_libcamera_src_negotiate(self)) {
GST_ELEMENT_FLOW_ERROR(self, GST_FLOW_NOT_NEGOTIATED);
gst_task_stop(self->task);
}
state->cam_->start(&state->initControls_);
}
/*
* Create and queue one request. If no buffers are available the
* function returns -ENOBUFS, which we ignore here as that's not a