are finished and the picture goes through the loop filters, the final picture representation is stored in the decoded picture buffer. Pictures stored in the decoded picture buffer can be used for the prediction of other pictures. HEVC was designed with the idea that progressive scan video would be used and no coding tools were added specifically for interlaced video. Interlace specific coding tools, such as MBAFF and PAFF, are not supported in HEVC. HEVC instead sends metadata that tells how the interlaced video was sent. Interlaced video may be sent either by coding each frame as a separate picture or by coding each field as a separate picture. For interlaced video HEVC can change between frame coding and field coding using Sequence Adaptive Frame Field (SAFF), which allows the coding mode to be changed for each video sequence. This allows interlaced video to be sent with HEVC without needing special interlaced decoding processes to be added to HEVC decoders. Color spaces The HEVC standard supports color spaces such as generic film, NTSC, PAL, Rec. 601, Rec. 709, Rec. 2020, Rec. 2100, SMPTE 170M, SMPTE 240M, sRGB, sYCC, xvYCC, XYZ, and externally specified color spaces. HEVC supports color encoding representations such as RGB, YCbCr, and YCoCg. Coding tools Coding tree unit HEVC replaces 16×16 pixel macroblocks, which were used with previous standards, with coding tree units (CTUs) which can use larger block structures of up to 64×64 samples and can better sub-partition the picture into variable sized structures. HEVC initially divides the picture into CTUs which can be 64×64, 32×32, or 16×16 with a larger pixel block size usually increasing the coding efficiency. Inverse transforms HEVC specifies four transform units (TUs) sizes of 4×4, 8×8, 16×16, and 32×32 to code the prediction residual. A CTB may be recursively partitioned into 4 or more TUs. TUs use integer basis functions based on the discrete cosine transform (DCT). In addition, 4×4 luma transform blocks that belong to an intra coded region are transformed using an integer transform that is derived from discrete sine transform (DST). This provides a 1% bit rate reduction but was restricted to 4×4 luma transform blocks due to marginal benefits for the other transform cases. Chroma uses the same TU sizes as luma so there is no 2×2 transform for chroma. Parallel processing tools Tiles allow for the picture to be divided into a grid of rectangular regions