v1.1.6

build/lib/pcv/examples/cam_video_switch.py

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+#!/usr/bin/env python
+
+from pcv.vidIO import VideoReader, OutOfFrames
+import cv2
+
+class VideoSwitcher:
+    ''' A class for switching between multiple videos. '''
+    def __init__(self, *filenames, track_along=True):
+        ''' Opens multiple videos for switching between.
+
+        When iterating, if a video completes it is re-started.
+
+        'track_along' is a boolean specifying if all the videos track along
+            together. Defaults to True, so when swapping to the next video it
+            gets jumped ahead to the number of frames that were covered since
+            it was last active. If set to False, swapping back to a video
+            resumes where it left off.
+
+        '''
+        self.filenames   = filenames
+        self.track_along = track_along
+        self.readers     = [self._initialise(video) for video in filenames]
+        self._counts     = [0 for video in filenames] # position of each video
+        self._count      = 0 # total frames processed
+        self.active      = 0 # current active video index
+
+    def _initialise(self, video):
+        ''' Initialise a video and its iterator. '''
+        reader = VideoReader(video, destroy=None, verbose=False)
+        iter(reader)
+        return reader
+
+    @property
+    def active(self):
+        return self._active
+
+    @active.setter
+    def active(self, value):
+        ''' Set a new reader as active. Track frames as required. '''
+        self._active = value
+        new_reader = self.readers[self._active]
+        if self.track_along:
+            extra = self._count - self._counts[self._active]
+            new_frame = (new_reader.frame + extra) % new_reader._end
+            new_reader.set_frame(new_frame)
+        new_reader.reset_delay() # avoid pause jump/negative delay
+
+    @property
+    def video(self):
+        return self.readers[self.active]
+
+    @video.setter
+    def video(self, replacement):
+        self.readers[self.active] = replacement
+
+    def __enter__(self):
+        ''' Ensure all VideoReaders are '''
+        for reader in self.readers:
+            reader.__enter__()
+
+        return self
+
+    def __exit__(self, *args):
+        ''' Clean up all the VideoReaders at context end. '''
+        for reader in self.readers:
+            try:
+                reader.__exit__(*args)
+            except:
+                continue
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        ''' Get the next video frame from the active video.
+
+        Restarts the active video first if it was finished.
+
+        '''
+        self._count += 1
+        self._counts[self.active] += 1
+        try:
+            return next(self.video)
+        except OutOfFrames:
+            return self._reinitialise_active_video()
+
+    def _reinitialise_active_video(self):
+        ''' Close and re-open the currently active video. '''
+        self.video.__exit__(None, None, None)
+        filename = self.filenames[self.active]
+        self.video = self._initialise(filename)
+        return next(self.video)
+
+    def next_video(self):
+        ''' Switch to the next video (circular buffer). '''
+        self.active = (self.active + 1) % len(self.readers)
+
+    def prev_video(self):
+        ''' Switch to the previous video (circular buffer). '''
+        self.active = (self.active - 1) % len(self.readers)
+
+    def set_active(self, index):
+        ''' Switch to a specified video index, modulo the number of videos. '''
+        self.active = index % len(self.readers)
+
+
+if __name__ == '__main__':
+    from os import listdir
+    from pcv.vidIO import Camera
+
+    class CoverAnalyser:
+        ''' Analyses a camera feed and switches videos when un/covered. '''
+        def __init__(self, video_switcher):
+            ''' Cycles through 'video_switcher' videos based on frame data. '''
+            self._video_switcher = video_switcher
+            self._covered = False
+
+        def analyse(self, frame):
+            ''' Switches to the next video if the camera is un/covered.
+
+            Switches on both camera cover and un-cover events.
+
+            Mean values of 40 and 60 were relevant for my camera when testing,
+                and may need to be different depending on camera and lighting.
+
+            '''
+            mean = frame.mean()
+            if (mean < 40 and not self._covered) \
+               or (mean > 50 and self._covered):
+                # switch to next video and toggle state
+                self._video_switcher.next_video()
+                self._covered ^= True # toggle state using boolean xor
+
+    videos = (file for file in listdir() if file.endswith('.mp4'))
+
+    print("press space to pause, 'q' to quit")
+    with VideoSwitcher(*videos) as video_switcher:
+        analyser = CoverAnalyser(video_switcher)
+        with Camera(0) as cam:
+            # zip together the videos and camera to progress in sync
+            for (_, v_frame), (_, c_frame) in zip(video_switcher, cam):
+                analyser.analyse(c_frame)
+                cv2.imshow('video', v_frame)