Adjusting method for video playback rate and video processing apparatus

Abstract

This invention provides a method and apparatus for adjusting video speed. In the method, a source video is provided. The source video consists of a continuous image of multiple frames. An adjustment instruction is received, and based on the adjustment instruction, multiple key frames and their corresponding playback speeds are determined from the continuous image of these frames. The input indices of the multiple key frames are mapped to a target function. The target function represents the mapping relationship between the input indices and the output indices. The target function forms a differentiable curve on a coordinate system, and the playback speed of the key frames corresponds to the slope of the corresponding point on the curve. The source video is sampled according to the input and output index relationship defined by the target function to generate an output video. This achieves a smooth video speed adjustment effect with precise control over the speed changes.

Claims

1. A method for adjusting video rate, implemented via a processor, the method comprising: A source video is provided, wherein the source video has a series of frames; an adjustment instruction is received, and a series of key frames and their corresponding playback rates are determined from the series of frames according to the adjustment instruction, wherein the series of frames in the source video are sorted according to their capture time points and are respectively assigned an index; the input indices of the key frames are mapped to an objective function, wherein the objective function represents the mapping relationship between the input indices and the output indices of the key frames, the objective function forms a curve on a coordinate system, each point on the curve is differentiable, the input indices of the key frames correspond to the first axis in the coordinate system, the output indices of the key frames correspond to the second axis in the coordinate system, and the playback rates corresponding to the key frames correspond to the slopes of the corresponding points on the curve; and the source video is sampled according to the input and output indices of the key frames to generate an output video; The sampling of the source video based on the input and output indices of the key frames includes: sampling the continuous image of the key frames in the source video in the direction of the previous capture time if the playback rate corresponding to one of the key frames is less than a first rate threshold; and sampling the continuous image of the key frames in the source video in the direction of the subsequent capture time if the playback rate corresponding to one of the key frames is not less than the first rate threshold.

2. The method for adjusting the video rate as described in claim 1, wherein the objective function is a quadratic function, and mapping the input indices of the key frames to the objective function includes: Determine the multiple coefficients in the quadratic function corresponding to these key image frames; And the input index of multiple cells in two adjacent keyframes is determined based on the univariate quadratic function with determined coefficients.

3. The video rate adjustment method as described in claim 1, wherein sampling the source video based on the input and output indices of the keyframes includes: If the playback rate corresponding to one of the key frames is not less than the first rate threshold and not greater than a second rate threshold, a new image is inserted between consecutive images of the frames in the source video, wherein the second rate threshold is greater than the first rate threshold.

4. The method for adjusting the video rate as described in claim 3, wherein inserting the new image between consecutive images of the frames in the source video comprises: The new image is generated by the weighted average of the pixels in consecutive images of two adjacent frames.

5. A video processing apparatus, comprising: A memory module used to store a piece of code; The system also includes a processor coupled to the memory and configured to load and execute the code: providing a source video having a series of frames; receiving an adjustment instruction and determining, according to the adjustment instruction, a series of keyframes and their corresponding playback rates from the series of frames, wherein the series of frames in the source video are ordered according to their capture time points and are assigned indices; mapping the input indices of the keyframes to an objective function, wherein the objective function represents the mapping relationship between the input indices and the output indices of the keyframes, the objective function forming a curve on a coordinate system, each point on the curve being differentiable, the input indices of the keyframes corresponding to a first axis in the coordinate system, the output indices of the keyframes corresponding to a second axis in the coordinate system, and the playback rates corresponding to the keyframes corresponding to the slopes of the corresponding points on the curve; and sampling the source video according to the input and output indices of the keyframes to generate an output video. The processor is further configured to: sample the continuous image of the frames in the source video in the direction of the previous capture time when the playback rate corresponding to one of the key frames is less than a first rate threshold; and sample the continuous image of the frames in the source video in the direction of the subsequent capture time when the playback rate corresponding to one of the key frames is not less than the first rate threshold.

6. The video processing apparatus of claim 5, wherein the objective function is a quadratic function, and the processor is further configured to: determine a plurality of coefficients in the quadratic function corresponding to the keyframes; and determine, based on the quadratic function having the determined coefficients, the input index of a plurality of frames in two adjacent keyframes among the keyframes.

7. The video processing apparatus of claim 5, wherein the processor is further configured to: insert a new image between consecutive images of the frames in the source video in response to a playback rate corresponding to one of the key frames not being less than the first rate threshold and not greater than a second rate threshold, wherein the second rate threshold is greater than the first rate threshold.

8. The video processing apparatus of claim 7, wherein the processor is further configured to: generate the new image based on a weighted average of pixels in consecutive images of two adjacent frames in the frames.

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