Determining native resolutions of video sequences
In one embodiment of the present invention, a native resolution analyzer generates a log-magnitude spectrum that elucidates sampling operations that have been performed on a scene. In operation, the native resolution analyzer performs a transform operation of a color component associated with a frame included in the scene to generate a frame spectrum. The native resolution analyzer then normalizes the magnitudes associated with the frame spectrum and logarithmically scales the normalized magnitudes to create a log-magnitude frame spectrum. This two dimensional log-magnitude frame spectrum serves as a frequency signature for the frame. More specifically, patterns in the log-magnitude spectrum reflect re-sampling operations, such as a down-sampling and subsequent up-sampling, that may have been performed on the frame. By analyzing the log-magnitude spectrum, discrepancies between the display resolution of the scene and the lowest resolution with which the scene has been processed may be detected in an automated fashion.
1. A computer-implemented method for generating spectra for characterizing re-sampling operations that have been performed on a scene within a video sequence and having a given display resolution, the method comprising:
performing a transform operation on a color component associated with a first frame included in the scene to generate a first frame spectrum;
normalizing a plurality of magnitudes associated with the first frame spectrum to generate a normalized first frame spectrum;
performing at least one operation on the normalized first frame spectrum to generate a first log-magnitude frame spectrum;
computing a native resolution associated with the scene based on the first log-magnitude frame spectrum, wherein the native resolution corresponds to at least one sampling operation performed on the scene.
2. The method of claim 1 , wherein the transform operation comprises a Discrete Fourier Transform.
3. The method of claim 1 , further comprising detecting and removing one or more black bars included in the video sequence to generate the scene.
4. The method of claim 1 , wherein the color component comprises one of a Y component, a Cb component, and a Cr component.
5. The method of claim 1 , further comprising:
generating a second log-magnitude frame spectrum associated with a second frame including in the scene; and
averaging the first log-magnitude frame spectrum and the second log-magnitude frame spectrum to generate a first log-magnitude scene spectrum.
6. The method of claim 1 , further comprising performing one or more pattern recognition operations on the first log-magnitude frame spectrum to determine a lowest resolution at which the first frame has been previously stored.
7. The method of claim 5 , further comprising performing one or more pattern recognition operations on the first log-magnitude scene spectrum to characterize an up-sampling technique implemented when generating the first frame.
8. The method of claim 1 , further comprising mapping each of the values included in the first log-magnitude frame spectrum to a range of gray-scale values to generate a first gray-scale log-magnitude frame spectrum.
9. A non-transitory computer-readable storage medium including instructions that, when executed by a processor, cause the processor to perform the steps of:
performing a transform operation on a color component associated with a first frame included in a scene to generate a first frame spectrum;
performing at least one operation on a plurality of magnitudes associated with the first frame spectrum to generate a first log-magnitude frame spectrum;
generating a second log-magnitude frame spectrum associated with a second frame including in the scene;
averaging the first log-magnitude frame spectrum and the second log-magnitude frame spectrum to generate a log-magnitude scene spectrum;
computing a native resolution associated with the scene based on the log-magnitude scene spectrum, wherein the native resolution corresponds to at least one sampling operation performed on the scene.
10. The computer-readable storage medium of claim 9 , wherein the transform operation comprises a Fast Fourier Transform.
11. The computer-readable storage medium of claim 9 , further comprising partitioning the video sequence into one or more scenes that include the scene.
12. The computer-readable storage medium of claim 9 , wherein the color component comprises one of an R component, a G component, and a B component.
13. The computer-readable storage medium of claim 9 , wherein performing the at least one operation on the plurality of magnitudes comprises:
normalizing the plurality of magnitudes to generate a normalized first frame spectrum; and
logarithmically scaling the normalized first frame spectrum.
14. The computer-readable storage medium of claim 9 , further comprising performing one or more pattern recognition operations on the log-magnitude scene spectrum to determine a lowest resolution at which the scene has been previously stored.
15. The computer-readable storage medium of claim 9 , further comprising mapping each of the values included in the log-magnitude scene spectrum to a range of gray-scale values to generate a gray-scale log-magnitude scene spectrum.
16. The computer-readable storage medium of claim 15 , wherein the range of gray-scale values comprises the values zero through 255 inclusive, and further comprising displaying the gray-scale log-magnitude scene spectrum to facilitate identifying a pattern that is characteristic of an up-sampling technique implemented when generating the first scene.
17. A system configured to generate spectra for characterizing up-sampling operations that have been performed on a scene within a video sequence, the system comprising:
a memory storing a native resolution analyzer; and
a processor coupled to the memory, wherein, when executed by the processor, the native resolution analyzer configures the processor to:
perform a transform operation on a color component associated with a first frame included in the scene to generate a first frame spectrum,
discard a plurality of phases associated with the first frame spectrum and retain a plurality of magnitudes associated with the first frame spectrum,
normalize the plurality of magnitudes to generate a normalized first frame spectrum, and
logarithmically scale the normalized first frame spectrum to generate a first log-magnitude frame spectrum.
18. The system of claim 17 , wherein the transform operation comprises one of a Discrete Fourier Transform and a Fast Fourier Transform.
19. The system of claim 17 , wherein the color component comprises one of a Y component, a Cb component, a Cr component, an R component, a G component, and a B component.
20. The system of claim 17 , wherein the native resolution analyzer further configures the processor to:
generate a second log-magnitude frame spectrum associated with a second frame including in the scene, and
average the first log-magnitude frame spectrum and the second log-magnitude frame spectrum to generate a first log-magnitude scene spectrum.