Dynamic synchronization of frame rate to a detected cadence in a time lapse image sequence
A frame rate is synchronized to a detected cadence in order to generate an output image sequence that is substantially stabilized. In an in-camera process, a camera receives motion data of the camera while the camera captures the sequence of image frames. A dominant frequency of motion is determined and the capture frame rate is dynamically adjusted to match the frequency of detected motion so that each image frame is captured when the camera is at approximately the same position along the axis of motion. Alternatively, in a post-processing process, frames of a captured image sequence are selectively sampled at a sampling rate corresponding to the dominant frequency of motion so that each sampled frame corresponds to an image capture that occurred when the camera is at approximately the same position along the axis of motion.
1. A method, comprising:
determining motion data of a camera during capture of a time lapse image sequence according to an initial frame rate, the motion data determined using one or more sensors tracking motion of the camera while the camera captures the time lapse image sequence;
determining a frequency of oscillation of the camera based on the motion data;
determining a modified frame rate based on the frequency of oscillation of the camera; and
capturing the time lapse image sequence according to the modified frame rate such that images of the time lapse image sequence are captured at an approximate same position of the camera.
2. The method of claim 1 , wherein determining the frequency of oscillation based on the motion data comprises:
converting the motion data from time domain data to frequency domain data; and
determining a dominant frequency in the frequency domain data.
3. The method of claim 2 , wherein the motion data is converted from the time domain data to the frequency domain data in a predefined time window.
4. The method of claim 2 , wherein the motion data is converted from the time domain data to the frequency domain data using Fast Fourier Transform.
5. The method of claim 2 , wherein determining the dominant frequency in the frequency domain data comprises:
determining a frequency value in the frequency domain data that has a largest amplitude of a plurality of frequency values in the frequency domain data; and
selecting the frequency value as the dominant frequency.
6. The method of claim 1 , wherein determining the modified frame rate based on the frequency of oscillation comprises:
setting the modified frame rate to match the frequency of oscillation.
7. The method of claim 1 , further comprising:
storing the time lapse image sequence to a storage medium.
8. The method of claim 1 , wherein the motion data comprises position data along an axis of oscillation.
9. A non-transitory computer-readable storage medium storing instructions, the instructions when executed by one or more processors cause the one or more processors to:
determine motion data of a camera during capture of a time lapse image sequence according to an initial frame rate, the motion data determined using one or more sensors of the camera;
determine information based on the motion data, the information comprising oscillation information of the camera by instructions to:
convert the motion data from time domain data to frequency domain data; and
determine frequency information in the frequency domain data;
determine a modified frame rate based on the information; and
capture the time lapse image sequence according to the modified frame rate such that images of the time lapse image sequence are captured at an approximate same position of the camera.
10. The non-transitory computer-readable storage medium of claim 9 , wherein the motion data is converted from the time domain data to the frequency domain data in a predefined time window.
11. The non-transitory computer-readable storage medium of claim 9 , wherein the motion data is converted from the time domain data to the frequency domain data using Fast Fourier Transform.
12. The non-transitory computer-readable storage medium of claim 9 , wherein to determine the frequency information in the frequency domain data comprises to:
determine a frequency value in the frequency domain data that has a largest amplitude of a plurality of frequency values in the frequency domain data; and
select the frequency value as the frequency information.
13. The non-transitory computer-readable storage medium of claim 9 , wherein to determine the modified frame rate based on the information comprises to:
set the modified frame rate to match the frequency information.
14. The non-transitory computer-readable storage medium of claim 9 , storing further instructions that when executed by the one or more processors cause the one or more processors to:
store the time lapse image sequence to a storage medium.
15. The non-transitory computer-readable storage medium of claim 9 , wherein the motion data comprises position data along an axis of oscillation.
16. The non-transitory computer-readable storage medium of claim 9 , wherein the modified frame rate is determined based on a dominant frequency of the frequency information.
17. An imaging device, comprising:
one or more processors; and
a non-transitory computer-readable storage medium storing instructions, the instructions when executed by the one or more processors causing the one or more processors to:
determine camera motion of a camera during capture of a time lapse image sequence, the camera motion comprising a cadence of motion of the camera;
determine a modified frame interval based on the cadence of the motion of the camera by converting the camera motion from time information to frequency information; and
continue capture of the time lapse image sequence according to the modified frame interval.
18. The imaging device of claim 17 , wherein the camera motion is converted from time information to frequency information using Fast Fourier Transform.
19. The imaging device of claim 17 , wherein the camera motion includes position data along an axis of oscillation.
20. The imaging device of claim 17 , wherein to continue capture of the time lapse image sequence according to the modified frame interval comprises to:
incrementally adjust a current capture frame to bring an initial capture frame rate closer to a dominant frequency of the frequency information.