# Data Embedding in SHVC Video Using Threshold-Controlled Block Splitting
## 4 Experimental Results
### Comparison with Conventional Methods  
For the purposes of fair comparison and analysis, the experiment environment and data set should be exactly the same, viz., using the same video encoder settings and the same video test sequences. However, we face three major challenges: (a) different video test sequences are used in the literature; (b) most experiments reported in the literature are conducted by using earlier video coding standards, and; (c) incomplete information about the parameter settings used for conducting experiments. These challenges prevent us from conducting and furnishing a thorough, fair and meaningful experiment using the conventional methods. Despite these challenges, we do however still provide a comparative analysis based on the available information for the completion of discussion. Specifically, for performance comparison, we define the embedding cost \(\gamma=(n_{e}-n_{o})/\rho\) as the number of bits spent on the video test sequence for encoding one payload bit, where \(n_{o}\) and \(n_{e}\) are the numbers of bits spent on coding (bit stream size) the original and processed video sequences, respectively, and \(\rho\) is number of payload bits embedded into the video sequence of interest. Based on the results, for \(\tau_{0}\), on average, 1.65 and 1.40 bits are required to embed 1 bit for the LDP and AI configurations, respectively. In comparison, to embed one payload bit into the video, [PERSON] et al's method for MPEG-2 video requires 5.36 bits, while [PERSON] et al. 's method for H.264 video requires 1.50 bits [39]. On the other hand, [PERSON] et al. 's embedding method implemented by using HEVC requires 1.69 bits [15]. When \(\tau\) is increased, more bits are spent to embed each payload bit because split blocks might be coded (instead of a bigger block), which required some signaling to the decoder. In other words, the increase in bit stream size is due to data embedding (i.e., a sub-optimal mode is selected hence larger prediction error) as well as additional signaling to the decoder. For example, for \(\tau_{5}\), the embedding cost falls in the range of \([3.09,6.75]\) and \([1.96,3.28]\) for the LDP and AI configurations, respectively. Similarly, for \(\tau_{10}\), the ranges are \([4.06,6.84]\) and \([2.30,3.43]\) for the LDP and AI configurations, respectively. Tables 6 and 7 record the embedding capacity for the proposed and conventional methods [15; 20; 21; 30] using the same QP settings. It is observed that the proposed method (which uses multiple syntax elements) achieves higher embedding capacity in comparison to the conventional methods (which uses a single syntax element) considered. The embedding capacity is doubled for LDP when both MVP and intra prediction mode are utilized for data embedding. It is also observed that higher embedding capacity is achieved for AI configuration. This is because more prediction modes are manipulated for data embedding in the proposed method. A relative functional comparison is conducted by considering the conventional methods proposed for MPEG-2 [19], H.264/AVC [39; 40], H.264/SVC [25; 31], and HEVC [15; 16; 20; 22; 23; 24; 41]. Table 8 compares the aforementioned methods in terms of embedding venue, applicability to intra/inter picture prediction, embedding capacity, video quality and bit rate overhead. Here, a relative comparison is performed because the results and values reported by the respective authors in the existing works are collected by using different test videos, video coding standards, parameter settings, etc. The labels of high (H), moderate (M)and low (L) are context-dependent and they are relative in nature. Firstly, for embedding capacity, we assign one of the three labels depending on the number of available syntax elements in a video. Specifically, more syntax elements provide more venues for data embedding, and vice versa [42]. While classical venues such as the coefficient offer high embedding capacity, recently identified venues (e.g., MVD in HEVC) will, in general, offer less embedding capacity.