IEC 62330-2-2003 pdf – Helical-scan digital video cassette recording system using 12,65 mm (0,5 in) magnetic tape – Format HD-D5 – Part 2: Compression format.
4 Video processing 4.1 Overview Luminance (Y) and colour difference components (C B and C R ) from 1 080i or 720p video signal are sampled by 74,25/1,001 MHz and 37,125/1,001 MHz respectively. After discarding samples in vertical and horizontal blanking periods, active video samples are divided into four super macro block groups (SMBG) per field (1 080i) or per frame (720p). Each SMBG consists of 1 080 super macro blocks (SMB). Each SMB consists of two MBs. Each MB consists of four luminance DCT blocks (8 × 4 pixel matrix) and one each of C B DCT block (8 × 8 pixel matrix) and C R DCT block (8 × 8 pixel matrix). As described later, two horizontally adjacent luminance DCT blocks are overlapped by one pixel column at their junction. Two horizontally adjacent chrominance DCT blocks are overlapped by one pixel column at their junction when they are formed into SMB. Each DCT block is transformed to represent DC and AC coefficients. Coefficients are weighted through the prearranged categories prior to shuffling, then formed into rearranged MBs (RMB). DCT coefficients within one rearranged MB group (RMBG) are quantized, and made into a fixed length data set through VLC. The VLC output code words from one RMBG are formed into 360 DIF blocks. The compressed video data for one 1 080i field or one 720p frame consists of 5 760 DIF blocks. The block diagram of the outline about video processing is shown in Figure 1.
4.3 Block formation 4.3.1 DCT block, macro block (MB) and super macro block (SMB) 126.96.36.199 DCT block The Y pixels in a field (1 080i system) and in a frame (720p system) shall be divided into rectangular areas of 15 horizontal pixels and 4 lines. Two Y DCT blocks (one Y DCT block pair) are made from each one of the rectangular areas as shown in Figure 4. In each Y DCT block pair, the rightmost pixel in the left DCT block is overlapped with the leftmost pixel in the right DCT block (overlapped blocking). The C B /C R pixels in a field (1 080i) and in a frame (720p) shall be divided into rectangular areas of 15 horizontal pixels and 8 lines. Two C DCT blocks (one C DCT block pair) are made from each one of the rectangular areas as shown in Figure 5. In each C DCT block pair, the rightmost pixel in the left block is overlapped with the leftmost pixel in the right block (overlapped blocking). Overlapped blocking is used for the robustness of error (see Annex A). Let r be the horizontal pixel position number in Y/C DCT block r = 0, 1, 2, …, 7. Let s be the vertical pixel position number in Y/C DCT block For Y block s = 0, 1, 2, 3 For C block s = 0, 1, 2, …, 7. Let P(r, s) be the value of the pixel at the position (r, s) 188.8.131.52 Macro block (MB) Each macro block (MB) in the 1 080i system and the 720p system consists of two Y DCT block pairs, one C B DCT block and one C R DCT block. Two Y DCT block pairs are vertically adjacent. C B DCT block and C R DCT block spatially correspond to the two Y DCT block pairs. Four Y DCT blocks (Ya, Yb, Yc, Yd), one C B DCT block and one C R DCT block are shown in Figure 6.