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obu: ignore operating_parameter_info in new sequence check

The operating_parameter_info is allowed to change in a single sequence.
Reorder Dav1dSequenceHeader so the check for new sequence can still be
done with memcmp and pffsetof.

--- a/include/dav1d/headers.h

+++ b/include/dav1d/headers.h

@@ -215,9 +215,6 @@

         int idc;

         int tier;

         int decoder_model_param_present;

-        int decoder_buffer_delay;

-        int encoder_buffer_delay;

-        int low_delay_mode;

         int display_model_param_present;

     } operating_points[DAV1D_MAX_OPERATING_POINTS];

@@ -258,6 +255,18 @@

     int color_description_present;

     int separate_uv_delta_q;

     int film_grain_present;

+

+    // Dav1dSequenceHeaders of the same sequence are required to be

+    // bit-identical until this offset. See 7.5 "Ordering of OBUs":

+    //   Within a particular coded video sequence, the contents of

+    //   sequence_header_obu must be bit-identical each time the

+    //   sequence header appears except for the contents of

+    //   operating_parameters_info.

+    struct Dav1dSequenceHeaderOperatingParameterInfo {

+        int decoder_buffer_delay;

+        int encoder_buffer_delay;

+        int low_delay_mode;

+    } operating_parameter_info[DAV1D_MAX_OPERATING_POINTS];

 } Dav1dSequenceHeader;

 typedef struct Dav1dSegmentationData {

--- a/src/obu.c

+++ b/src/obu.c

@@ -112,6 +112,8 @@

         for (int i = 0; i < hdr->num_operating_points; i++) {

             struct Dav1dSequenceHeaderOperatingPoint *const op =

                 &hdr->operating_points[i];

+            struct Dav1dSequenceHeaderOperatingParameterInfo *const opi =

+                &hdr->operating_parameter_info[i];

             op->idc = dav1d_get_bits(gb, 12);

             op->major_level = 2 + dav1d_get_bits(gb, 3);

             op->minor_level = dav1d_get_bits(gb, 2);

@@ -119,11 +121,11 @@

             op->decoder_model_param_present =

                 hdr->decoder_model_info_present && dav1d_get_bits(gb, 1);

             if (op->decoder_model_param_present) {

-                op->decoder_buffer_delay =

+                opi->decoder_buffer_delay =

                     dav1d_get_bits(gb, hdr->encoder_decoder_buffer_delay_length);

-                op->encoder_buffer_delay =

+                opi->encoder_buffer_delay =

                     dav1d_get_bits(gb, hdr->encoder_decoder_buffer_delay_length);

-                op->low_delay_mode = dav1d_get_bits(gb, 1);

+                opi->low_delay_mode = dav1d_get_bits(gb, 1);

             }

             op->display_model_param_present =

                 hdr->display_model_info_present && dav1d_get_bits(gb, 1);

@@ -1241,7 +1243,9 @@

         // previous state. Free that state.

         if (!c->seq_hdr)

             c->frame_hdr = NULL;

-        else if (memcmp(seq_hdr, c->seq_hdr, sizeof(*seq_hdr))) {

+        // see 7.5, operating_parameter_info is allowed to change in

+        // sequence headers of a single sequence

+        else if (memcmp(seq_hdr, c->seq_hdr, offsetof(Dav1dSequenceHeader, operating_parameter_info))) {

             c->frame_hdr = NULL;

             c->mastering_display = NULL;

             c->content_light = NULL;