Method and system for video processing to determine digital pulse recognition tones
In one aspect, the present disclosure relates to a method for isolating a broadcast digital pulse recognition tone of a beacon light source in a digital video sequence. In some embodiments, the method includes receiving a digital video sequence of a scene, the digital video sequence including a sequence of frames and the scene including both modulated illumination broadcast by a beacon light source and un-modulated illumination, calculating a background value of the digital video sequence, the background value including a portion of the digital video sequence corresponding to the un-modulated illumination of the scene, subtracting the background value of the digital video sequence to obtain an isolated digital video sequence of the modulated illumination of the scene, calculating a frequency content of a frame of the isolated digital video sequence, and determining a particular tone broadcast by the beacon light source based on the frequency content.
1. A method for isolating a broadcast digital pulse recognition tone of a beacon light source in a digital video sequence, the method comprising:
electronically receiving, by an image sensor of a mobile device, a digital video sequence of a scene, wherein the digital video sequence comprises a sequence of frames and the scene comprises both modulated illumination broadcast by a beacon light source and un-modulated illumination;
calculating a background value of the digital video sequence, wherein the background value comprises a portion of the digital video sequence corresponding to the un-modulated illumination of the scene;
subtracting the background value of the digital video sequence from the digital video sequence to obtain an isolated digital video sequence of the modulated illumination of the scene;
calculating a frequency content of a frame of the isolated digital video sequence; and
determining a particular symbol broadcast by the beacon light source based on the frequency content; wherein each frame of the sequence of frames comprises a plurality of pixel values, each of the plurality of pixel values having a given point in the frame, and calculating the background value comprises analyzing the plurality of pixel values of each given point of a subset of the sequence of frames.
2. The method of claim 1 , comprising accumulating the subset of the frames in a frame buffer.
3. The method of claim 1 , wherein the averaging is performed using a technique comprising one of calculating a simple numerical average, calculating a normalized average, calculating a Gaussian average, or calculating the frame difference between subsequent frames.
4. The method of claim 1 , comprising applying a motion compensation technique to transform each frame prior to calculating the background value.
5. The method of claim 4 , wherein the motion compensation technique comprises one of shifting or transforming each frame of the sequence of frames to substantially overlie the previous frame.
6. The method of claim 4 , wherein the motion compensation technique comprises one of kernel density estimation, Eigenbackground, or mean-shift based estimation.
7. An image detection apparatus for isolating a broadcast digital pulse recognition tone of a beacon light source in a digital video sequence comprising:
an imaging sensor; and
a processor in communication with the imaging sensor configured to receive a digital video sequence comprising a sequence of frames of a scene comprising both modulated illumination broadcast by the beacon light source and un-modulated illumination, calculate a background value comprising a portion of the digital video sequence corresponding to the un-modulated illumination of the scene of the digital video sequence, subtract the background value of the digital video sequence from the digital video sequence to obtain an isolated digital video sequence of the modulated illumination of the scene, calculate a frequency content of a frame of the isolated digital video sequence, and determine a particular symbol broadcast by the beacon light source based on the frequency content; wherein each frame of the sequence of frames comprises a plurality of pixel values, each of the plurality of pixel values having a given point in the frame and the processor is configured to calculate the background value by analyzing the plurality of pixel values of each given point of a subset of the sequence of frames.
8. The image detection apparatus of claim 7 , further comprising a frame buffer accessible by the processor, wherein the processor is configured to accumulate the subset of the frames in a frame buffer.
9. The image detection apparatus of claim 7 , wherein the processor is configured to perform the averaging using a technique comprising one of calculating a simple numerical average, calculating a normalized average, calculating a Gaussian average, or calculating the frame difference between subsequent frames.
10. The image detection apparatus of claim 7 , wherein the processor is configured to apply a motion compensation technique to transform each frame prior to calculating the background value.
11. The image detection apparatus of claim 10 , wherein the motion compensation technique comprises one of shifting or transforming each frame of the sequence of frames to substantially overlie the previous frame.
12. The image detection apparatus of claim 10 , wherein the motion compensation technique comprises one of using kernel density estimation, Eigenbackground, or mean-shift based estimation.