NekoCWD/libcamera
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gstreamer: Fix libcamerasrc responding latency before setting caps

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Whenever a downstream element queries latency, libcamerasrc will always reply,
even though it has not yet determined the latency.

However some downstream elements (e.g. glvideomixer/aggregator) will query the
latency before libcamerasrc sets the caps. When these elements get the latency,
they will start the caps negotiation. Since libcamerasrc has not yet determined
caps, invalid negotiation is performed and workflow is disrupted.

So, set latency to 'GST_CLOCK_TIME_NONE' during initialization, and reply to the
query after libcamerasrc confirms the latency. At this time, libcamerasrc has also
completed caps negotiation and downstream elements work fine.

In addition, every time the src pad task stops, we reset the latency to
GST_CLOCK_TIME_NONE to ensure that when next time task starts, the downstream
elements can generate out buffers after receiving the effective latency.

Signed-off-by: Hou Qi <qi.hou@nxp.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
Hou Qi 2025-06-05 15:37:41 +09:00 • committed by Kieran Bingham
parent b4c92a61bf
commit 4a277906a4
2 changed files with 8 additions and 1 deletions
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5
src/gstreamer/gstlibcamerapad.cpp
View file

@ -72,6 +72,10 @@ gst_libcamera_pad_query(GstPad *pad, GstObject *parent, GstQuery *query)
if (query->type != GST_QUERY_LATENCY) if (query->type != GST_QUERY_LATENCY)
return gst_pad_query_default(pad, parent, query); return gst_pad_query_default(pad, parent, query);
GLibLocker lock(GST_OBJECT(self));
if (self->latency == GST_CLOCK_TIME_NONE)
return FALSE;
/* TRUE here means live, we assumes that max latency is the same as min /* TRUE here means live, we assumes that max latency is the same as min
* as we have no idea that duration of frames. */ * as we have no idea that duration of frames. */
gst_query_set_latency(query, TRUE, self->latency, self->latency); gst_query_set_latency(query, TRUE, self->latency, self->latency);
@ -81,6 +85,7 @@ gst_libcamera_pad_query(GstPad *pad, GstObject *parent, GstQuery *query)
static void static void
gst_libcamera_pad_init(GstLibcameraPad *self) gst_libcamera_pad_init(GstLibcameraPad *self)
{ {
self->latency = GST_CLOCK_TIME_NONE;
GST_PAD_QUERYFUNC(self) = gst_libcamera_pad_query; GST_PAD_QUERYFUNC(self) = gst_libcamera_pad_query;
} }

4
src/gstreamer/gstlibcamerasrc.cpp
View file

@ -881,8 +881,10 @@ gst_libcamera_src_task_leave([[maybe_unused]] GstTask *task,
{ {
GLibRecLocker locker(&self->stream_lock); GLibRecLocker locker(&self->stream_lock);
for (GstPad *srcpad : state->srcpads_) for (GstPad *srcpad : state->srcpads_) {
gst_libcamera_pad_set_latency(srcpad, GST_CLOCK_TIME_NONE);
gst_libcamera_pad_set_pool(srcpad, nullptr); gst_libcamera_pad_set_pool(srcpad, nullptr);
}
} }
g_clear_object(&self->allocator); g_clear_object(&self->allocator);