MASTER THESIS Video Watermarking - Computer Graphics Group ...

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5.3 Time Consumption This section discusses time consumption of both the embedding and the detection pipelines. The time has been measured by standard Unix utility called time; the user-space time has been considered only. Average results of three iterations in Table 3 show that all the methods are basically equivalent in embedding but noise method is the worst in detection because of visual data decoding. The test has been executed on a machine with the following configuration: Intel Pentium M (Centrino) processor, 1.60GHz, 3200 bogomips 512MB DDR PC2700 memory, 333MHz openSUSE 10.1 operating system Table 3: Time consumption test results The test has proved that the plugin is applicable in practice. 5.4 Robustness Robustness test scripts simulate real attacks applied either intentionally or unintentionally to watermarked video sequences. In the simulations, they have been executed on pre-filtered watermarked sequences – the sequences have been remuxed in order to contain (besides parameter sets) intra coded slices only because the watermark is embedded into intra coded slices only. Most of the tests proceeds as follows. A watermarked pre-filtered sequence is converted using MPlayer to the raw video stream of single images, one image per frame. During the conversion, the video signal processing filter is applied eventually. Then, the raw stream is compressed by x264 encoder producing H.264 video stream at the former bit-rate with intra coded slices only, and muxed to the Matroska container format. The recompression at the former bit-rate obviously impairs the embedded watermark but the attacks are simulated more faithfully. The impairment rate of recompression is measured in Section 5.4.1. Finally, the detection process takes place in such an attacked sequence. The 40
probabilities of watermark detection success given by the detector are summarized in tables in the following sections. 5.4.1 Recompression This test uses MPlayer with no filter applied. Recompression is applied at four different bit-rates – at the former bit-rate (100%) and at 75%, 50% and 25% of the former bit-rate. The results are summarized in Table 4 where the bit-rate ratios are listed in column named BR. Table 4: Recompression test results All three methods are robust at similar level. Watermarks from all video sequences have been successfully detected after recompression at up to 50% of the former bit-rate; from some sequences even after recompression at 25% of the former bit-rate. Only the recompression of Wildlife using noise method with weight factor of 1 can be considered to be a successful attack. The watermark is impaired the most in Renaissance because of the greatest bit-rate growth during watermark embedding. Note that the watermark quite resists to recompression at the former bit-rate, thus the results of the other tests using recompression are distorted only a bit. 41
Page 1 and 2: Charles University in Prague Facult
Page 3 and 4: Table of Contents Abstract 5 1 Intr
Page 5 and 6: Název práce: Watermarking videa A
Page 7 and 8: information about copyright owner a
Page 9 and 10: Common geometric distortions - the
Page 11 and 12: watermark, i.e. values of the water
Page 13 and 14: Chapter 3 The H.264 Standard The H.
Page 15 and 16: There are three types of slices: I,
Page 17 and 18: frequency transform. The choice is
Page 19 and 20: Chapter 4 Implementation Details Th
Page 21 and 22: auxiliary coded pictures), Supplem
Page 23 and 24: an intra coded slice, content ID -
Page 25 and 26: samples is subtracted from the resi
Page 27 and 28: At the beginning of the entire proc
Page 29 and 30: file in order to provide detailed r
Page 31 and 32: as a part of the whole process. The
Page 33 and 34: coefficients are hardly set to non-
Page 35 and 36: Table 1 outlines characteristics of
Page 37 and 38: The third and the fourth row sets c
Page 39: Using block method, we cannot consi
Page 43 and 44: 5.4.3 Cropping In the cropping test
Page 45 and 46: 5.4.6 Blurring Blurring can be cons
Page 47 and 48: 5.4.8 Multiple Watermark Embedding
Page 49 and 50: Despite the expectations, all the m
Page 51 and 52: ecompression and noising, and to so
Page 53 and 54: Bibliography [1] Ingemar J. Cox, Jo
Page 55 and 56: Appendix A Enclosed CD & Installati
Page 57 and 58: Appendix B The plugin usage The wat
Page 59: length is the length of the list of

MASTER THESIS Video Watermarking - Computer Graphics Group ...

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