Description: Don't update sps if they are only repeated
Origin: https://github.com/strukturag/libde265/pull/372
From 51f07f132f29832e025a8b913b61cbd20257c5fc Mon Sep 17 00:00:00 2001
From: Tobias Frost <tobi@debian.org>
Date: Fri, 13 Jan 2023 12:22:45 +0100
Subject: [PATCH] Don't update sps if they are only repeated

This is an attempt to improve the mitigations from #365 and #366 and picks up an idea I described at #345:

> One way would be just to look at the pointers of the SPS (fast and easy, but
> may reject more than required), or investigate if the SPS used for the image
> generations are "compatible".

This changes do exactly this: It (very conservativly) checks if the old and new sps have
identical information -- except the reference picture set, which I believe is supposed
to be updated by new sps'). If they are basically identical, the old sps will be
used instead of the new one, (of course, reference image set is updated from the new one)

I'm using standalone operator== and helper functions to avoid changing ABI of the library;
if an ABI bump would be done, of course this should go to the respective classes.
---
 libde265/decctx.cc | 273 +++++++++++++++++++++++++++++++++++++++++++++
 libde265/sps.cc    |   6 +
 2 files changed, 279 insertions(+)

diff --git a/libde265/decctx.cc b/libde265/decctx.cc
index 6701725f..0000b25d 100644
--- a/libde265/decctx.cc
+++ b/libde265/decctx.cc
@@ -545,6 +545,263 @@ de265_error decoder_context::read_vps_NAL(bitreader& reader)
   return DE265_OK;
 }
 
+// implemented as freestanding functions to avoid changing API
+
+bool operator==(const profile_data &lhs, const profile_data &rhs) {
+	if(&lhs == &rhs) return true;
+	if(lhs.profile_present_flag != rhs.profile_present_flag ) return false;
+	if(lhs.profile_present_flag) {
+		if(lhs.profile_space != rhs.profile_space ) return false;
+		if(lhs.tier_flag != rhs.tier_flag ) return false;
+		if(lhs.profile_idc != rhs.profile_idc ) return false;
+
+		if(memcmp(lhs.profile_compatibility_flag, rhs.profile_compatibility_flag, sizeof(rhs.profile_compatibility_flag)) ) return false;
+
+		if(lhs.progressive_source_flag != rhs.progressive_source_flag ) return false;
+		if(lhs.interlaced_source_flag != rhs.interlaced_source_flag ) return false;
+		if(lhs.non_packed_constraint_flag != rhs.non_packed_constraint_flag ) return false;
+		if(lhs.frame_only_constraint_flag != rhs.frame_only_constraint_flag ) return false;
+	}
+
+	if(lhs.level_present_flag != rhs.level_present_flag) return false;
+	if(lhs.level_present_flag && lhs.level_idc != rhs.level_idc ) return false;
+
+	return true;
+}
+
+bool operator!=(const profile_data &lhs, const profile_data &rhs) {
+	if(&lhs == &rhs) return false;
+	return (!(lhs==rhs));
+}
+
+// class does not store max_sub_layers, so operator == cannot be done.
+bool isEqual(const profile_tier_level &lhs , const profile_tier_level &rhs,  int sps_max_sub_layers ) {
+	if(&lhs == &rhs) return true;
+
+	if(lhs.general != rhs.general ) return false;
+	for(int i = 0 ; i < sps_max_sub_layers; i++ ) {
+		if(lhs.sub_layer[i] != rhs.sub_layer[i]) return false;
+	}
+	return true;
+}
+
+bool isEqual(const video_usability_information &lhs, const video_usability_information &rhs, const seq_parameter_set &sps) {
+	if(&lhs == &rhs) return true;
+
+	// not seen yet if(lhs.nal_hrd_parameters_present_flag != rhs.nal_hrd_parameters_present_flag ) return false;
+
+	// populated by video_usability_information::read()
+	if(lhs.aspect_ratio_info_present_flag != rhs.aspect_ratio_info_present_flag ) return false;
+	if(lhs.aspect_ratio_info_present_flag) {
+		if(lhs.sar_width != rhs.sar_width ) return false;
+		if(lhs.sar_height != rhs.sar_height ) return false;
+	}
+
+	if(lhs.overscan_info_present_flag != rhs.overscan_info_present_flag ) return false;
+	if(lhs.overscan_info_present_flag) {
+		if(lhs.overscan_appropriate_flag != rhs.overscan_appropriate_flag ) return false;
+	}
+
+	if(lhs.video_signal_type_present_flag != rhs.video_signal_type_present_flag ) return false;
+	if(lhs.video_signal_type_present_flag) {
+		if(lhs.video_format != rhs.video_format ) return false;
+		if(lhs.video_full_range_flag != rhs.video_full_range_flag) return false;
+		if(lhs.colour_description_present_flag != rhs.colour_description_present_flag) return false;
+		if(lhs.colour_primaries != rhs.colour_primaries ) return false;
+		if(lhs.transfer_characteristics != rhs.transfer_characteristics ) return false;
+		if(lhs.matrix_coeffs != rhs.matrix_coeffs ) return false;
+	}
+
+	if(lhs.chroma_loc_info_present_flag != rhs.chroma_loc_info_present_flag ) return false;
+	if(lhs.chroma_loc_info_present_flag) {
+		if(lhs.chroma_sample_loc_type_top_field != rhs.chroma_sample_loc_type_top_field ) return false;
+		if(lhs.chroma_sample_loc_type_bottom_field != rhs.chroma_sample_loc_type_bottom_field ) return false;
+	}
+	if(lhs.neutral_chroma_indication_flag != rhs.neutral_chroma_indication_flag ) return false;
+	if(lhs.field_seq_flag != rhs.field_seq_flag ) return false;
+	if(lhs.frame_field_info_present_flag != rhs.frame_field_info_present_flag ) return false;
+
+	if(lhs.default_display_window_flag != rhs.default_display_window_flag ) return false;
+	if(lhs.default_display_window_flag) {
+		if(lhs.def_disp_win_left_offset != rhs.def_disp_win_left_offset ) return false;
+		if(lhs.def_disp_win_right_offset != rhs.def_disp_win_right_offset ) return false;
+		if(lhs.def_disp_win_top_offset != rhs.def_disp_win_top_offset ) return false;
+		if(lhs.def_disp_win_bottom_offset != rhs.def_disp_win_bottom_offset ) return false;
+	}
+
+	if(lhs.vui_timing_info_present_flag != rhs.vui_timing_info_present_flag ) return false;
+	if(lhs.vui_timing_info_present_flag) {
+		if(lhs.vui_num_units_in_tick != rhs.vui_num_units_in_tick ) return false;
+		if(lhs.vui_time_scale != rhs.vui_time_scale ) return false;
+		if(lhs.vui_timing_info_present_flag != rhs.vui_timing_info_present_flag ) return false;
+		if(lhs.vui_timing_info_present_flag) {
+			if(lhs.vui_num_ticks_poc_diff_one != rhs.vui_num_ticks_poc_diff_one ) return false;
+		}
+	}
+
+	if(lhs.vui_hrd_parameters_present_flag != rhs.vui_hrd_parameters_present_flag ) return false;
+
+
+	if(lhs.vui_hrd_parameters_present_flag) {
+		// check things made by hrd_parametes
+
+		if(lhs.vui_hrd_parameters_present_flag != rhs.vui_hrd_parameters_present_flag ) return false;
+		if(lhs.vcl_hrd_parameters_present_flag != rhs.vcl_hrd_parameters_present_flag ) return false;
+
+		if(lhs.nal_hrd_parameters_present_flag || lhs.vcl_hrd_parameters_present_flag) {
+			if(lhs.sub_pic_hrd_params_present_flag != rhs.sub_pic_hrd_params_present_flag ) return false;
+			if(lhs.sub_pic_hrd_params_present_flag) {
+				if(lhs.tick_divisor_minus2 != rhs.tick_divisor_minus2 ) return false;
+				if(lhs.du_cpb_removal_delay_increment_length_minus1 != rhs.du_cpb_removal_delay_increment_length_minus1 ) return false;
+				if(lhs.sub_pic_cpb_params_in_pic_timing_sei_flag != rhs.sub_pic_cpb_params_in_pic_timing_sei_flag ) return false;
+				if(lhs.dpb_output_delay_du_length_minus1 != rhs.dpb_output_delay_du_length_minus1 ) return false;
+			}
+			if(lhs.bit_rate_scale != rhs.bit_rate_scale ) return false;
+			if(lhs.cpb_size_scale != rhs.cpb_size_scale ) return false;
+			if(lhs.sub_pic_hrd_params_present_flag) {
+				if(lhs.cpb_size_du_scale != rhs.cpb_size_du_scale ) return false;
+			}
+			if(lhs.initial_cpb_removal_delay_length_minus1 != rhs.initial_cpb_removal_delay_length_minus1 ) return false;
+			if(lhs.au_cpb_removal_delay_length_minus1 != rhs.au_cpb_removal_delay_length_minus1 ) return false;
+			if(lhs.dpb_output_delay_length_minus1 != rhs.dpb_output_delay_length_minus1 ) return false;
+		}
+
+		int  i;
+		unsigned int  j, nalOrVcl;
+
+		for (i = 0; i < sps.sps_max_sub_layers; i++) {
+			if(lhs.fixed_pic_rate_general_flag[i] != rhs.fixed_pic_rate_general_flag[i] ) return false;
+			if(lhs.fixed_pic_rate_general_flag[i]) {
+				if(lhs.elemental_duration_in_tc_minus1[i] != rhs.elemental_duration_in_tc_minus1[i] ) return false;
+			}
+			if(lhs.low_delay_hrd_flag[i] != rhs.low_delay_hrd_flag[i] ) return false;
+			if(lhs.cpb_cnt_minus1[i] != rhs.cpb_cnt_minus1[i] ) return false;
+
+			for (nalOrVcl = 0; nalOrVcl < 2; nalOrVcl++) {
+				if (((nalOrVcl == 0) && lhs.nal_hrd_parameters_present_flag) || ((nalOrVcl == 1) && lhs.vcl_hrd_parameters_present_flag)) {
+					for (j = 0; j <= lhs.cpb_cnt_minus1[i]; j++) {
+						if(lhs.bit_rate_value_minus1[i][j][nalOrVcl] != rhs.bit_rate_value_minus1[i][j][nalOrVcl]) return false;
+						if(lhs.cpb_size_value_minus1[i][j][nalOrVcl] != rhs.cpb_size_value_minus1[i][j][nalOrVcl]) return false;
+
+						if (lhs.sub_pic_hrd_params_present_flag) {
+							if(lhs.cpb_size_du_value_minus1[i][j][nalOrVcl] != rhs.cpb_size_du_value_minus1[i][j][nalOrVcl]) return false;
+							if(lhs.bit_rate_du_value_minus1[i][j][nalOrVcl] != rhs.bit_rate_du_value_minus1[i][j][nalOrVcl]) return false;
+						}
+						if( lhs.cbr_flag[i][j][nalOrVcl] != rhs.cbr_flag[i][j][nalOrVcl]) return false;
+					}
+				}
+			}
+		}
+	}
+	return true;
+}
+
+bool operator==(const sps_range_extension &lhs, const sps_range_extension &rhs) {
+	if(&lhs == &rhs) return true;
+    if(lhs.transform_skip_rotation_enabled_flag != rhs.transform_skip_rotation_enabled_flag ) return false;
+    if(lhs.transform_skip_context_enabled_flag != rhs.transform_skip_context_enabled_flag ) return false;
+    if(lhs.implicit_rdpcm_enabled_flag != rhs.implicit_rdpcm_enabled_flag ) return false;
+    if(lhs.explicit_rdpcm_enabled_flag != rhs.explicit_rdpcm_enabled_flag ) return false;
+    if(lhs.extended_precision_processing_flag != rhs.extended_precision_processing_flag ) return false;
+    if(lhs.intra_smoothing_disabled_flag != rhs.intra_smoothing_disabled_flag ) return false;
+    if(lhs.high_precision_offsets_enabled_flag != rhs.high_precision_offsets_enabled_flag ) return false;
+    if(lhs.persistent_rice_adaptation_enabled_flag != rhs.persistent_rice_adaptation_enabled_flag ) return false;
+    if(lhs.cabac_bypass_alignment_enabled_flag != rhs.cabac_bypass_alignment_enabled_flag ) return false;
+	return true;
+}
+
+bool operator!=(const sps_range_extension &lhs, const sps_range_extension &rhs) {
+	if(&lhs == &rhs) return false;
+	return !(lhs==rhs);
+}
+
+
+bool operator==(const seq_parameter_set &lhs, const seq_parameter_set &rhs) {
+
+	if(&lhs== &rhs) return true;
+
+	if(lhs.sps_read != rhs.sps_read) return false;
+
+	if(lhs.video_parameter_set_id != rhs.video_parameter_set_id) return false;
+	if(lhs.sps_max_sub_layers != rhs.sps_max_sub_layers) return false;
+	if(lhs.sps_temporal_id_nesting_flag != rhs.sps_temporal_id_nesting_flag) return false;
+
+	if(!isEqual(lhs.profile_tier_level_, rhs.profile_tier_level_, lhs.sps_max_sub_layers)) return false;
+
+	if(lhs.seq_parameter_set_id != rhs.seq_parameter_set_id) return false;
+	if(lhs.chroma_format_idc != rhs.chroma_format_idc) return false;
+
+	if(lhs.separate_colour_plane_flag != rhs.separate_colour_plane_flag) return false;
+	if(lhs.pic_width_in_luma_samples != rhs.pic_width_in_luma_samples) return false;
+	if(lhs.pic_height_in_luma_samples != rhs.pic_height_in_luma_samples) return false;
+	if(lhs.conformance_window_flag != rhs.conformance_window_flag) return false;
+
+	if(lhs.conformance_window_flag) {
+		if(lhs.conf_win_left_offset != rhs.conf_win_left_offset) return false;
+		if(lhs.conf_win_right_offset != rhs.conf_win_right_offset) return false;
+		if(lhs.conf_win_top_offset != rhs.conf_win_top_offset) return false;
+		if(lhs.conf_win_bottom_offset != rhs.conf_win_bottom_offset) return false;
+	}
+
+	if(lhs.bit_depth_luma != rhs.bit_depth_luma) return false;
+	if(lhs.bit_depth_chroma != rhs.bit_depth_chroma) return false;
+
+	if(lhs.log2_max_pic_order_cnt_lsb != rhs.log2_max_pic_order_cnt_lsb) return false;
+	if(lhs.sps_sub_layer_ordering_info_present_flag != rhs.sps_sub_layer_ordering_info_present_flag) return false;
+
+	if(memcmp(lhs.sps_max_dec_pic_buffering, rhs.sps_max_dec_pic_buffering, sizeof(rhs.sps_max_dec_pic_buffering))) return false;
+	if(memcmp(lhs.sps_max_num_reorder_pics, rhs.sps_max_num_reorder_pics,  sizeof(rhs.sps_max_num_reorder_pics))) return false;
+	if(memcmp(lhs.sps_max_latency_increase_plus1, rhs.sps_max_latency_increase_plus1,  sizeof(rhs.sps_max_latency_increase_plus1))) return false;
+
+	if(lhs.log2_min_luma_coding_block_size != rhs.log2_min_luma_coding_block_size) return false;
+	if(lhs.log2_diff_max_min_luma_coding_block_size != rhs.log2_diff_max_min_luma_coding_block_size) return false;
+	if(lhs.log2_min_transform_block_size != rhs.log2_min_transform_block_size) return false;
+	if(lhs.log2_diff_max_min_transform_block_size != rhs.log2_diff_max_min_transform_block_size) return false;
+	if(lhs.max_transform_hierarchy_depth_inter != rhs.max_transform_hierarchy_depth_inter) return false;
+	if(lhs.max_transform_hierarchy_depth_intra != rhs.max_transform_hierarchy_depth_intra) return false;
+
+	if(lhs.scaling_list_enable_flag != rhs.scaling_list_enable_flag) return false;
+	if(lhs.scaling_list_enable_flag) {
+		if(lhs.sps_scaling_list_data_present_flag != rhs.sps_scaling_list_data_present_flag) return false;
+		if(lhs.sps_scaling_list_data_present_flag) {
+			// compare only needed if present, otherwise it is the default scaling list.
+			if(memcmp(&lhs.scaling_list, &rhs.scaling_list, sizeof(rhs.scaling_list))) return false;
+		}
+	}
+
+	if(lhs.amp_enabled_flag != rhs.amp_enabled_flag) return false;
+	if(lhs.sample_adaptive_offset_enabled_flag != rhs.sample_adaptive_offset_enabled_flag) return false;
+	if(lhs.pcm_enabled_flag != rhs.pcm_enabled_flag) return false;
+
+	if(lhs.pcm_enabled_flag) {
+		if(lhs.pcm_sample_bit_depth_luma != rhs.pcm_sample_bit_depth_luma) return false;
+		if(lhs.pcm_sample_bit_depth_chroma != rhs.pcm_sample_bit_depth_chroma) return false;
+		if(lhs.log2_min_pcm_luma_coding_block_size != rhs.log2_min_pcm_luma_coding_block_size) return false;
+		if(lhs.log2_diff_max_min_pcm_luma_coding_block_size != rhs.log2_diff_max_min_pcm_luma_coding_block_size) return false;
+		if(lhs.pcm_loop_filter_disable_flag != rhs.pcm_loop_filter_disable_flag) return false;
+	}
+
+	// (longterm) reference pics likely to change with a new sps, so ignored here.
+
+	if(lhs.sps_temporal_mvp_enabled_flag != rhs.sps_temporal_mvp_enabled_flag) return false;
+	if(lhs.strong_intra_smoothing_enable_flag != rhs.strong_intra_smoothing_enable_flag) return false;
+
+	if(lhs.vui_parameters_present_flag != rhs.vui_parameters_present_flag) return false;
+	if(lhs.vui_parameters_present_flag) {
+		if(!isEqual(lhs.vui, rhs.vui, lhs )) return false;
+	}
+
+	if(lhs.sps_extension_present_flag != rhs.sps_extension_present_flag ) return false;
+	if(lhs.sps_extension_present_flag) {
+		if(lhs.sps_range_extension_flag != rhs.sps_range_extension_flag ) return false;
+		if(lhs.sps_multilayer_extension_flag != rhs.sps_multilayer_extension_flag ) return false;
+		if(lhs.sps_extension_6bits != rhs.sps_extension_6bits ) return false;
+		if(lhs.range_extension != rhs.range_extension) return false;
+	}
+
+	return true;
+}
+
 de265_error decoder_context::read_sps_NAL(bitreader& reader)
 {
   logdebug(LogHeaders,"----> read SPS\n");
@@ -560,6 +817,22 @@ de265_error decoder_context::read_sps_NAL(bitreader& reader)
     new_sps->dump(param_sps_headers_fd);
   }
 
+  if ( sps[ new_sps->seq_parameter_set_id ] ) {
+	  auto old_sps = sps[ new_sps->seq_parameter_set_id ].get();
+	  if ( *old_sps == *new_sps ) {
+		  // printf(" **** keeping sps *****\n");
+		  // the new sps is identical to the old one, so no replacing needed.
+		  // however, reference pics and long-term reference pics might need updating.
+		  old_sps->ref_pic_sets = new_sps->ref_pic_sets;
+		  old_sps->long_term_ref_pics_present_flag = new_sps->long_term_ref_pics_present_flag;
+		  memcpy(old_sps->lt_ref_pic_poc_lsb_sps, new_sps->lt_ref_pic_poc_lsb_sps,  sizeof(old_sps->lt_ref_pic_poc_lsb_sps));
+		  memcpy(old_sps->used_by_curr_pic_lt_sps_flag, new_sps->used_by_curr_pic_lt_sps_flag,  sizeof(old_sps->used_by_curr_pic_lt_sps_flag));
+		  return DE265_OK;
+	  }
+	  //printf(" **** replacing sps *****\n");
+
+  }
+
   sps[ new_sps->seq_parameter_set_id ] = new_sps;
 
   // Remove the all PPS that referenced the old SPS because parameters may have changed and we do not want to
diff --git a/libde265/sps.cc b/libde265/sps.cc
index f1c28255..31ce9470 100644
--- a/libde265/sps.cc
+++ b/libde265/sps.cc
@@ -287,6 +287,11 @@ de265_error seq_parameter_set::read(error_queue* errqueue, bitreader* br)
   int firstLayer = (sps_sub_layer_ordering_info_present_flag ?
                     0 : sps_max_sub_layers-1 );
 
+  // zero out so that comparing is easier.
+  memset(sps_max_dec_pic_buffering, 0 , sizeof(sps_max_dec_pic_buffering));
+  memset(sps_max_num_reorder_pics, 0 , sizeof(sps_max_num_reorder_pics));
+  memset(sps_max_latency_increase_plus1, 0 , sizeof(sps_max_latency_increase_plus1));
+
   for (int i=firstLayer ; i <= sps_max_sub_layers-1; i++ ) {
 
     // sps_max_dec_pic_buffering[i]
@@ -347,6 +352,7 @@ de265_error seq_parameter_set::read(error_queue* errqueue, bitreader* br)
     if (sps_scaling_list_data_present_flag) {
 
       de265_error err;
+      memset(&scaling_list, 0 , sizeof(scaling_list));  // zero out, so that memcmp will do it to check for equality.
       if ((err=read_scaling_list(br,this, &scaling_list, false)) != DE265_OK) {
         return err;
       }