Offload QR detector to external process to retain good FPS

latency_measure.py

@@ -5,6 +5,8 @@ From: https://github.com/perrytsao/Webcam-Latency-Measurement/blob/master/Camera
 """
 
 from collections import deque
+from multiprocessing import Process, Queue
+import queue
 import time
 import timeit
 import numpy as np
@@ -34,10 +36,9 @@ class Source:
 class GigE(Source):
     def __init__(self):
         self.camera = neoapi.Cam()
-        # self.camera.Connect('-B127')   
-        self.camera.Connect('-B105')   
+        self.camera.Connect()
         # Default buffer mode, streaming, always returns latest frame
-        self.camera.SetImageBufferCount(10)
+        self.camera.SetImageBufferCount(2)
         # neoAPI docs: Setting the neoapi.Cam.SetImageBufferCycleCount()to one ensures that all buffers but one are given back to the neoAPI to be re-cycled and never given to the user by the neoapi.Cam.GetImage() method.
         self.camera.SetImageBufferCycleCount(1) 
         if self.camera.IsConnected(): 
@@ -45,9 +46,18 @@ class GigE(Source):
             self.camera.f.BinningHorizontal.Set(2)
             self.camera.f.BinningVertical.Set(2)
         self.pixfmt = self.camera.f.PixelFormat.Get()
+        self._last_timestamp = None
     
     def recv(self):
-        i = self.camera.GetImage(0)    
+        i = self.camera.GetImage(0)
+
+        # check that we're not getting an older image from the buffer
+        # because buffer is LIFO
+        ts = i.GetTimestamp()
+        if self._last_timestamp is not None and self._last_timestamp > ts:
+            return None
+        self._last_timestamp = ts
+
         if i.IsEmpty():
             return None
 
@@ -61,13 +71,32 @@ class GigE(Source):
             img = cv2.convertScaleAbs(img, alpha=(255.0/65535.0))
         return img
 
+def qr_detector(frame_q: Queue, intervals_q: Queue):
+    while True:
+        now, img_for_qr = frame_q.get()
+
+        code,bbox,rectifiedImage = qrDecoder.detectAndDecode(img_for_qr)
+        if len(code) > 0:
+            detected_t = float(code)
+            try:
+                intervals_q.put_nowait(now-detected_t)
+            except queue.Full as e:
+                pass
+            # latencies.append(now-detected_t)
+
+
 source = GigE()
 
+# pass frames to QR detector process
+frame_q = Queue(2)
+# pass detected intervals back from detector process
+intervals_q = Queue(20)
+
 
 
 config = pyglet.gl.Config(sample_buffers=1, samples=4)
 
-display = pyglet.canvas.get_display()
+display = pyglet.display.get_display()
 screen = display.get_screens()[0]
 print(screen)
 window = pyglet.window.Window(width=screen.width, height=screen.height, config=config, fullscreen=True, screen=screen)
@@ -92,20 +121,12 @@ def check_frames(dt: float):
     img = cv2.flip(cv2.cvtColor(img, cv2.COLOR_BGR2RGB), 0)
 
     # TODO: offload to queue and multiprocessing
-    img_for_qr = cv2.resize(img, (0,0), fx=.1, fy=.1)
-    retval, codes,bboxes,rectifiedImages = qrDecoder.detectAndDecodeMulti(img)
+    # img_for_qr = cv2.resize(img, (0,0), fx=.1, fy=.1)
+    try:
+        frame_q.put_nowait((now, img))
+    except queue.Full as e:
+        pass
     
-    if retval:
-        # print(retval, codes)
-        for code in codes:
-            if len(code) == 0:
-                continue
-                
-            # TODO)) Handle/filter/sort multiple QRs
-            # I.e. filter out newest, and only go for single most new.
-            # In that case we should verify there's >=2 QRs in sight.
-            detected_t = float(code)
-            latencies.append(now - detected_t)
         
 
     img_data = pyglet.image.ImageData(img.shape[1], img.shape[0], 'RGB', img.tobytes())
@@ -121,6 +142,12 @@ def on_refresh(dt):
     
     if qr_sprite is not None:
         qr_sprite.delete() # clear texture from memory
+
+    try:
+        latency = intervals_q.get_nowait()
+        latencies.append(latency)
+    except queue.Empty as e:
+        pass
     
     intervals = [video_fps[i] - video_fps[i-1] for i in range(1, len(video_fps))]
     
@@ -187,6 +214,7 @@ window.set_handler('on_draw', on_draw)
 try:
     event_loop = pyglet.app.EventLoop()
     pyglet.clock.schedule(check_frames)
+    Process(target=qr_detector, args=(frame_q, intervals_q), daemon=True).start()
     event_loop.run()
 finally:
     window.close()