As hardware for reproducing and storing high resolution or high quality video content is being developed and supplied, a need for a video codec for effectively encoding or decoding the high resolution or high quality video content is increasing. According to a conventional video codec, a video is encoded according to a limited encoding method based on a macroblock having a predetermined size.
Image data of a spatial region is transformed into coefficients of a frequency region via frequency transformation. According to a video codec, an image is split into blocks having a predetermined size, discrete cosine transformation (DCT) is performed on each block, and frequency coefficients are encoded in block units, for rapid calculation of frequency transformation. Compared with image data of a spatial region, coefficients of a frequency region are easily compressed. In particular, since an image pixel value of a spatial region is expressed according to a prediction error via inter prediction or intra prediction of a video codec, when frequency transformation is performed on the prediction error, a large amount of data may be transformed to 0. According to a video codec, an amount of data may be reduced by replacing data that is consecutively and repeatedly generated with small-sized data.
A multi-layer video codec encodes and decodes a first layer video and at least one second layer video. Amounts of data of the first layer video and the second layer video may be reduced by removing temporal/spatial redundancy and layer redundancy of the first layer video and the second layer video.
Meanwhile, when subblock-based inter-layer prediction is performed, subblock size information is signaled. Here, since the subblock size information is signaled without considering at all a case in which the subblock size is less than a minimum size of a coding unit or is greater than a maximum size of the coding unit, realization/operation complexity of encoding and decoding apparatuses unnecessarily increases. Also, the signaled subblock size information includes information about a block having a size that is not used as a prediction unit, and thus the number of bits may be unnecessarily wasted.
Also, when the subblock-based inter-layer prediction is performed, since a subblock is determined without considering a prediction unit allowed in an existing codec, compatibility with the existing codec is low.