diff --git a/libavcodec/h266.h b/libavcodec/h266.h
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+++ b/libavcodec/h266.h
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+/*
+ * H.266 shared code
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_H266_H
+#define AVCODEC_H266_H
+
+/**
+ * Table 5 – NAL unit type codes and NAL unit type classes in
+ * T-REC-H.266-202008
+ */
+enum H266NALUnitType {
+    H266_NAL_TRAIL       = 0,
+    H266_NAL_STSA        = 1,
+    H266_NAL_RADL        = 2,
+    H266_NAL_RASL        = 3,
+    H266_NAL_RSV_VCL_4   = 4,
+    H266_NAL_RSV_VCL_5   = 5,
+    H266_NAL_RSV_VCL_6   = 6,
+    H266_NAL_IDR_W_RADL  = 7,
+    H266_NAL_IDR_N_LP    = 8,
+    H266_NAL_CRA_NUT     = 9,
+    H266_NAL_GDR_NUT     = 10,
+    H266_NAL_RSV_IRAP_11 = 11,
+    H266_NAL_OPI         = 12,
+    H266_NAL_DCI         = 13,
+    H266_NAL_VPS         = 14,
+    H266_NAL_SPS         = 15,
+    H266_NAL_PPS         = 16,
+    H266_NAL_PREFIX_APS  = 17,
+    H266_NAL_SUFFIX_APS  = 18,
+    H266_NAL_PH          = 19,
+    H266_NAL_AUD         = 20,
+    H266_NAL_EOS_NUT     = 21,
+    H266_NAL_EOB_NUT     = 22,
+    H266_NAL_PREFIX_SEI  = 23,
+    H266_NAL_SUFFIX_SEI  = 24,
+    H266_NAL_FD_NUT      = 25,
+    H266_NAL_RSV_NVCL_26 = 26,
+    H266_NAL_RSV_NVCL_27 = 27,
+    H266_NAL_UNSPEC_28   = 28,
+    H266_NAL_UNSPEC_29   = 29,
+    H266_NAL_UNSPEC_30   = 30,
+    H266_NAL_UNSPEC_31   = 31,
+};
+
+enum H266SliceType {
+    H266_SLICE_B = 0,
+    H266_SLICE_P = 1,
+    H266_SLICE_I = 2,
+};
+
+enum {
+    H266_MAX_PLANES = 3,
+    //7.4.3.3 The value of vps_max_sublayers_minus1 shall be in the range of 0 to 6, inclusive
+    H266_MAX_SUB_LAYERS = 7,
+
+    // 7.3.2.3: vps_video_parameter_set_id is u(4).
+    H266_MAX_VPS_COUNT = 16,
+    // 7.3.2.4: sps_seq_parameter_set_id is in [0, 15].
+    H266_MAX_SPS_COUNT = 16,
+    // 7.3.2.5: pps_pic_parameter_set_id is in [0, 63].
+    H266_MAX_PPS_COUNT = 64,
+
+    // A.4.2: MaxDpbSize is bounded above by 16.
+    H266_MAX_DPB_SIZE = 16,
+
+    //7.4.3.4 sps_num_ref_pic_lists in range [0, 64]
+    H266_MAX_REF_PIC_LISTS = 64,
+
+    //7.4.3.3 sps_num_points_in_qp_table_minus1[i] in range [0, 36 − sps_qp_table_start_minus26[i]],
+    //sps_qp_table_start_minus26[i] in range [sps_qp_table_start_minus26[i] −26 − QpBdOffset, 36]
+    //for 10 bitsQpBdOffset is 12, so sps_num_points_in_qp_table_minus1[i] in range [0, 74]
+    H266_MAX_POINTS_IN_QP_TABLE = 75,
+
+    // 7.4.6.1: hrd_cpb_cnt_minus1 is in [0, 31].
+    H266_MAX_CPB_CNT = 32,
+
+    // A.4.1: in table A.6 the highest level allows a MaxLumaPs of 35 651 584.
+    H266_MAX_LUMA_PS = 35651584,
+    // A.4.1: pic_width_in_luma_samples and pic_height_in_luma_samples are
+    // constrained to be not greater than sqrt(MaxLumaPs * 8).  Hence height/
+    // width are bounded above by sqrt(8 * 35651584) = 16888.2 samples.
+    H266_MAX_WIDTH  = 16888,
+    H266_MAX_HEIGHT = 16888,
+
+    // A.4.1: table A.1 allows at most 20 tile rows for any level.
+    H266_MAX_TILE_ROWS    = 20,
+    // A.4.1: table A.1 allows at most 20 tile columns for any level.
+    H266_MAX_TILE_COLUMNS = 20,
+
+    // A.4.1 table A.1 allows at most 600 slice for any level.
+    H266_MAX_SLICES = 600,
+
+    // 7.4.8: in the worst case (tiles_enabled_flag and
+    // entropy_coding_sync_enabled_flag are both set), entry points can be
+    // placed at the beginning of every Ctb row in every tile, giving an
+    // upper bound of (num_tile_columns_minus1 + 1) * PicHeightInCtbsY - 1.
+    // Only a stream with very high resolution and perverse parameters could
+    // get near that, though, so set a lower limit here with the maximum
+    // possible value for 8K video (at most 135 32x32 Ctb rows).
+    H266_MAX_ENTRY_POINT_OFFSETS = H266_MAX_TILE_COLUMNS * 135,
+};
+
+#endif /* AVCODEC_H266_H */
