# Data Embedding in SHVC Video Using Threshold-Controlled Block Splitting
## 4 Experimental Results
### Comparison with Conventional Methods
In addition, it is observed that the quality degradation for coefficient-based methods [25; 39] and coding block structure-based methods [22; 23; 24] falls in the range of \([0.2,4.8]\) dB and \([1.0,2.3]\) dB, respectively. Since the quality is slightly inferior in comparison to the former, it is labeled'M' for these methods. Subsequently, we analyze the impact of data embedding on the bit rate based on these works. Generally, when more bits are embedded into a video sequence, the bit rate overhead will be higher. Besides that, more bits are required to code the non-optimal block structure or predicted values, as well as additional syntax elements resulting from data embedding. Therefore, when more changes to the syntax elements or more syntax elements are coded due to data embedding, the bit rate overhead increases accordingly. These findings are consistent with the observation. Specifically, it is observed that the number of MVD is relatively low as compared to other syntax elements, and the bit rate overhead incurred is less than 1% [19]. A coding block and its neighboring blocks are usually correlated with each other and they contain the same moving object with similar motion. The MV after mapping the merging block to the payload bit is likely to be maintained. Therefore, the bit rate overhead after manipulating merge mode can be maintained at a relatively low value (e.g., 2.3% as reported in [43]). Since the bit rate overhead is maintained at a minimum level, these methods are labeled as 'L'. On the other hand, the bit rate overhead caused by using the intra prediction mode to embed data in [15] is capped at 4%, while the bit rate overhead caused by manipulating coding block structure falls in the range of [5; 5.5] in [PERSON] et al. 's method [24]. In addition, the bit rate overhead caused by manipulating coefficient falls in the range of [1.4, 5.0] in [PERSON] et al. 's method [39] and [PERSON] et al. 's method [25]. Since the bit rate overhead for these methods is relatively higher in comparison to the former methods, they are labeled as 'M'. In general, all considered methods embed data during the encoding process. However, depending on the eventual mode of encoding of a block (i.e., MB in H.264 or CU in HEVC/SHVC), most existing methods may or may not be able to embed data. For example, the intra picture prediction-based method will not be able to embed data into a block when the inter picture prediction mode turns out to be more cost effective (hence the block is coded by the using inter prediction mode), and vice versa. On the other hand, the proposed method is able to embed data into both intra and inter predicted blocks. In other words, eventually one mode will be chosen (i.e., intra or inter), and in any case, data can be embedded by the proposed method. Similar to the proposed method, [PERSON] et al. 's method [22] can embed data in each CU since block size is exploited, while Shanableh [23] offers the same capability by exploiting the block-splitting flag. Since technology constantly advances to newer standards, we also evaluate the feasibility of applying the conventional data embedding methods to the SHVC standard. The MVD in [19] is not feasible for data embedding in EL when an inter-layer reference picture is utilized in EL, because all MVs are set to _zero_ to fulfil the requirement of bit stream conformance in EL(s) [44]. On the other hand, when the fast encoder mode setting is enabled, only blocks with size \(2N\times 2N\) are coded, hence any method that is based on block partitioning (e.g., [23]) can only be applied to BL, unless the fast encoder mode is disabled. Likewise, although a coefficient-based method can be easily adopted in SHVC, propagation of error should be handled carefully to avoid poor perceptual quality for inter-layer predicted picture.