3 files changed, 45 insertions(+), 9 deletions(-)

M src/camera.c
M src/camera.h
M src/io_pipeline.c

@@ 1178,6 1178,31 @@ control_impl_int32(MPCamera *camera, uint32_t id, int request, int32_t *value)
 	return true;
 }
 
+void
+mp_camera_control_set_int32_bg(MPCamera *camera, uint32_t id, int32_t v)
+{
+	struct v4l2_ext_control ctrl = {};
+	ctrl.id = id;
+	ctrl.value = v;
+
+	struct v4l2_ext_controls ctrls = {
+		.ctrl_class = 0,
+		.which = V4L2_CTRL_WHICH_CUR_VAL,
+		.count = 1,
+		.controls = &ctrl,
+	};
+
+	int fd = control_fd(camera);
+
+	// fork only after all the memory has been read
+	if (fork() != 0)
+		return; // discard errors, nothing to do in parent process
+	// ignore errors
+	xioctl(fd, VIDIOC_S_EXT_CTRLS, &ctrls);
+	// exit without calling exit handlers
+	_exit(0);
+}
+
 bool
 mp_camera_control_try_int32(MPCamera *camera, uint32_t id, int32_t *v)
 {


@@ 1221,3 1246,10 @@ mp_camera_control_get_bool(MPCamera *camera, uint32_t id)
 	control_impl_int32(camera, id, VIDIOC_G_EXT_CTRLS, &v);
 	return v;
 }
+
+void
+mp_camera_control_set_bool_bg(MPCamera *camera, uint32_t id, bool v)
+{
+	int32_t value = v;
+	return mp_camera_control_set_int32_bg(camera, id, value);
+}

@@ 111,7 111,11 @@ bool mp_camera_query_control(MPCamera *camera, uint32_t id, MPControl *control);
 bool mp_camera_control_try_int32(MPCamera *camera, uint32_t id, int32_t *v);
 bool mp_camera_control_set_int32(MPCamera *camera, uint32_t id, int32_t v);
 int32_t mp_camera_control_get_int32(MPCamera *camera, uint32_t id);
+// set the value in the background, discards result
+void mp_camera_control_set_int32_bg(MPCamera *camera, uint32_t id, int32_t v);
 
 bool mp_camera_control_try_bool(MPCamera *camera, uint32_t id, bool *v);
 bool mp_camera_control_set_bool(MPCamera *camera, uint32_t id, bool v);
 bool mp_camera_control_get_bool(MPCamera *camera, uint32_t id);
+// set the value in the background, discards result
+void mp_camera_control_set_bool_bg(MPCamera *camera, uint32_t id, bool v);

@@ 199,7 199,7 @@ setup_camera(MPDeviceList **device_list, const struct mp_camera_config *config)
 		if (mp_camera_query_control(info->camera, V4L2_CID_FOCUS_AUTO,
 					    NULL)) {
 			info->has_auto_focus_continuous = true;
-			mp_camera_control_set_bool(info->camera, V4L2_CID_FOCUS_AUTO,
+			mp_camera_control_set_bool_bg(info->camera, V4L2_CID_FOCUS_AUTO,
 						   true);
 		}
 		if (mp_camera_query_control(info->camera, V4L2_CID_AUTO_FOCUS_START,


@@ 362,10 362,10 @@ update_controls()
 
 	if (want_focus) {
 		if (info->has_auto_focus_continuous) {
-			mp_camera_control_set_bool(info->camera, V4L2_CID_FOCUS_AUTO,
+			mp_camera_control_set_bool_bg(info->camera, V4L2_CID_FOCUS_AUTO,
 						   1);
 		} else if (info->has_auto_focus_start) {
-			mp_camera_control_set_bool(info->camera,
+			mp_camera_control_set_bool_bg(info->camera,
 						   V4L2_CID_AUTO_FOCUS_START, 1);
 		}
 


@@ 373,19 373,19 @@ update_controls()
 	}
 
 	if (current_controls.gain_is_manual != desired_controls.gain_is_manual) {
-		mp_camera_control_set_bool(info->camera, V4L2_CID_AUTOGAIN,
+		mp_camera_control_set_bool_bg(info->camera, V4L2_CID_AUTOGAIN,
 					   !desired_controls.gain_is_manual);
 	}
 
 	if (desired_controls.gain_is_manual &&
 	    current_controls.gain != desired_controls.gain) {
-		mp_camera_control_set_int32(info->camera, info->gain_ctrl,
+		mp_camera_control_set_int32_bg(info->camera, info->gain_ctrl,
 					    desired_controls.gain);
 	}
 
 	if (current_controls.exposure_is_manual !=
 	    desired_controls.exposure_is_manual) {
-		mp_camera_control_set_int32(info->camera, V4L2_CID_EXPOSURE_AUTO,
+		mp_camera_control_set_int32_bg(info->camera, V4L2_CID_EXPOSURE_AUTO,
 					    desired_controls.exposure_is_manual ?
 						    V4L2_EXPOSURE_MANUAL :
 						    V4L2_EXPOSURE_AUTO);


@@ 393,7 393,7 @@ update_controls()
 
 	if (desired_controls.exposure_is_manual &&
 	    current_controls.exposure != desired_controls.exposure) {
-		mp_camera_control_set_int32(info->camera, V4L2_CID_EXPOSURE,
+		mp_camera_control_set_int32_bg(info->camera, V4L2_CID_EXPOSURE,
 					    desired_controls.exposure);
 	}
 


@@ 444,13 444,13 @@ on_frame(MPBuffer buffer, void * _data)
 
 			// Restore the auto exposure and gain if needed
 			if (!current_controls.exposure_is_manual) {
-				mp_camera_control_set_int32(info->camera,
+				mp_camera_control_set_int32_bg(info->camera,
 							    V4L2_CID_EXPOSURE_AUTO,
 							    V4L2_EXPOSURE_AUTO);
 			}
 
 			if (!current_controls.gain_is_manual) {
-				mp_camera_control_set_bool(info->camera,
+				mp_camera_control_set_bool_bg(info->camera,
 							   V4L2_CID_AUTOGAIN, true);
 			}