MASTER THESIS Video Watermarking - Computer Graphics Group ...

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partitioning into slices (see Section 3.1.2) and entropy coding (see Section 3.2). Usually, there is only one SPS and one PPS in the stream at the beginning. A set of NAL units compounding exactly one picture of the video sequence is called access unit, as depicted in Figure 2. A picture is either the whole frame of the video sequence or one of two frame fields. One field contains odd rows of the frame while the other contains even ones. 3.1.2 Slices Figure 2: NAL units sequence One picture can be partitioned into several slices, each coded in separate NAL unit. The shape of slices is basically arbitrary, slices can even blend together, but usually they form almost the same horizontal strips, as in Figure 3. Figure 3: Partitioning of a picture into slices 14
There are three types of slices: I, P and B. I slices are completely intra coded (no reference pictures are used for prediction) while P and B slices use inter coding, i.e. previous pictures in display order (and in case of B slices, following pictures as well) are used for prediction. Intra coding may provide access points to the video sequence where decoding can begin and continue correctly, but typically gains only moderate compression efficiency in comparison with inter coding. The intra prediction process consist in exploiting of spatial statistical dependencies in a single picture while the inter prediction process exploits temporal statistical dependencies between different pictures. The prediction processes are thoroughly described in Section 3.2. Only the pictures that go in the stream before the current slice can be used for prediction. Thus, even following pictures in display order used for prediction should go before the current slice. The reason is simple: decoders need those pictures to be able to decode predicted slices on-the-fly. Let us assume that each picture consists of a single slice, then the difference between display and stream order is illustrated in Figure 4 and Figure 5 (prediction dependencies are indicated by arrows). 3.1.3 Macroblocks Figure 4: Display order of pictures Figure 5: Stream order of pictures A slice is a sequence of macroblocks, as depicted in Figure 3. A macroblock, consisting of a 16×16 block of luma samples and two corresponding blocks of chroma samples, is used as the basic processing unit. Luma samples represent luminance of pixels while chroma samples represent chromatic components. 15
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: Chapter 3 The H.264 Standard The H.
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 and 40: Using block method, we cannot consi
Page 41 and 42: probabilities of watermark detectio
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

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