25-08-2017, 09:32 PM
Digital Video Watermarking using Discrete Wavelet Transform and Principal Component Analysis
Digital Video.pptx (Size: 1.54 MB / Downloads: 22)
Objective:
A hybrid digital video watermarking scheme based on Discrete Wavelet Transform (DWT) and Principal Component Analysis (PCA) is proposed for copyright protection of digital video applications.
Watermarking:
Watermarking is the process that embeds data called a watermark or digital signature into a multimedia object such that watermark can be detected or extracted later to make an assertion about the object.
Video watermarking introduces a number of issues not present in image watermarking.
Due to inherent redundancy between video frames, video signals are highly susceptible to attacks such as frame averaging, frame dropping, frame swapping and statistical analysis.
DWT:
DWT is more computationally efficient than other transform methods like DFT and DCT.
DWT decomposes an image or a video frame into sub-images,3 details and 1 approximation.
It separates the frequency band of an image into a lower resolution approximation sub-band (LL) as well as horizontal (HL),vertical (LH) and diagonal (HH) detail components.
Embedding the watermark in low frequencies increases the robustness with respect to attacks that have low pass characteristics.
PCA:
PCA is basically used to hybridize the algorithm as it has the inherent property of removing the correlation amongst the data.
The number of principal components is less than or equal to the number of original variables.
PCA is a method of identifying patterns in data, and expressing the data in such a way so as to highlight their similarities and differences.
Frame dropping
Frame dropping means dropping one or more frames randomly from the watermarked video sequence.
If we drop too many frames, the quality of the watermarked video will decrease rapidly.
In our experiment, we only drop one frame randomly.
Frame swapping
Frame swapping means switching the order of frames randomly within a watermarked video sequence.
If we swap too many frames, it will degrade the video quality.
We have extracted all the watermarks from the video after frame swapping.
Frame averaging
Since the frames are watermarked with the same information, the watermarked videos are not subject to the risk of watermark estimation by frame averaging since the watermark signal gets amplified on averaging.
Conclusion
The algorithm implemented using DWT-PCA is robust and imperceptible in nature and embedding the binary watermark in the low LL sub band helps in increasing the robustness of the embedding procedure without much degradation in the video quality.
As a future work the video frames can be subject to scene change analysis to embed an independent watermark in the sequence of frames forming a scene, and repeating this procedure for all the scenes within a video.