hevc: Improve stream constraint values in common header

Add comments to describe the sources of the constraint values expressed here,
and add some more related values which will be used in following patches.

Fix the incorrect values for SPS and PPS count (they are not the same as those
used for H.264), and remove HEVC_MAX_CU_SIZE because it is not used anywhere.

(cherry picked from commit b88da98b34809dedf8882d43ed543632ed233538)

1 files changed, 53 insertions, 12 deletions

diff --git a/libavcodec/hevc.h b/libavcodec/hevc.h
index f0fb919a7f..2f20db8285 100644
--- a/libavcodec/hevc.h
+++ b/libavcodec/hevc.h
@@ -74,19 +74,60 @@ enum HEVCSliceType {
     HEVC_SLICE_I = 2,
 };
 
-/**
- * 7.4.2.1
- */
-#define HEVC_MAX_SUB_LAYERS 7
-#define HEVC_MAX_VPS_COUNT 16
-#define HEVC_MAX_SPS_COUNT 32
-#define HEVC_MAX_PPS_COUNT 256
-#define HEVC_MAX_SHORT_TERM_RPS_COUNT 64
-#define HEVC_MAX_CU_SIZE 128
+enum {
+    // 7.4.3.1: vps_max_layers_minus1 is in [0, 62].
+    HEVC_MAX_LAYERS     = 63,
+    // 7.4.3.1: vps_max_sub_layers_minus1 is in [0, 6].
+    HEVC_MAX_SUB_LAYERS = 7,
+    // 7.4.3.1: vps_num_layer_sets_minus1 is in [0, 1023].
+    HEVC_MAX_LAYER_SETS = 1024,
+
+    // 7.4.2.1: vps_video_parameter_set_id is u(4).
+    HEVC_MAX_VPS_COUNT = 16,
+    // 7.4.3.2.1: sps_seq_parameter_set_id is in [0, 15].
+    HEVC_MAX_SPS_COUNT = 16,
+    // 7.4.3.3.1: pps_pic_parameter_set_id is in [0, 63].
+    HEVC_MAX_PPS_COUNT = 64,
+
+    // A.4.2: MaxDpbSize is bounded above by 16.
+    HEVC_MAX_DPB_SIZE = 16,
+    // 7.4.3.1: vps_max_dec_pic_buffering_minus1[i] is in [0, MaxDpbSize - 1].
+    HEVC_MAX_REFS     = HEVC_MAX_DPB_SIZE,
+
+    // 7.4.3.2.1: num_short_term_ref_pic_sets is in [0, 64].
+    HEVC_MAX_SHORT_TERM_REF_PIC_SETS = 64,
+    // 7.4.3.2.1: num_long_term_ref_pics_sps is in [0, 32].
+    HEVC_MAX_LONG_TERM_REF_PICS      = 32,
 
-#define HEVC_MAX_REFS 16
-#define HEVC_MAX_DPB_SIZE 16 // A.4.1
+    // A.3: all profiles require that CtbLog2SizeY is in [4, 6].
+    HEVC_MIN_LOG2_CTB_SIZE = 4,
+    HEVC_MAX_LOG2_CTB_SIZE = 6,
+
+    // E.3.2: cpb_cnt_minus1[i] is in [0, 31].
+    HEVC_MAX_CPB_CNT = 32,
+
+    // A.4.1: in table A.6 the highest level allows a MaxLumaPs of 35 651 584.
+    HEVC_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.
+    HEVC_MAX_WIDTH  = 16888,
+    HEVC_MAX_HEIGHT = 16888,
+
+    // A.4.1: table A.6 allows at most 22 tile rows for any level.
+    HEVC_MAX_TILE_ROWS    = 22,
+    // A.4.1: table A.6 allows at most 20 tile columns for any level.
+    HEVC_MAX_TILE_COLUMNS = 20,
+
+    // 7.4.7.1: 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 4K video (at most 135 16x16 Ctb rows).
+    HEVC_MAX_ENTRY_POINT_OFFSETS = HEVC_MAX_TILE_COLUMNS * 135,
+};
 
-#define HEVC_MAX_LOG2_CTB_SIZE 6
 
 #endif /* AVCODEC_HEVC_H */