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diff --git a/media/libjxl/src/lib/jxl/headers.h b/media/libjxl/src/lib/jxl/headers.h
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+++ b/media/libjxl/src/lib/jxl/headers.h
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+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#ifndef LIB_JXL_HEADERS_H_
+#define LIB_JXL_HEADERS_H_
+
+// Codestream headers, also stored in CodecInOut.
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "lib/jxl/aux_out_fwd.h"
+#include "lib/jxl/base/compiler_specific.h"
+#include "lib/jxl/base/status.h"
+#include "lib/jxl/dec_bit_reader.h"
+#include "lib/jxl/enc_bit_writer.h"
+#include "lib/jxl/field_encodings.h"
+
+namespace jxl {
+
+// Reserved by ISO/IEC 10918-1. LF causes files opened in text mode to be
+// rejected because the marker changes to 0x0D instead. The 0xFF prefix also
+// ensures there were no 7-bit transmission limitations.
+static constexpr uint8_t kCodestreamMarker = 0x0A;
+
+// Compact representation of image dimensions (best case: 9 bits) so decoders
+// can preallocate early.
+class SizeHeader : public Fields {
+ public:
+  // All fields are valid after reading at most this many bits. WriteSizeHeader
+  // verifies this matches Bundle::MaxBits(SizeHeader).
+  static constexpr size_t kMaxBits = 78;
+
+  SizeHeader();
+  JXL_FIELDS_NAME(SizeHeader)
+
+  Status VisitFields(Visitor* JXL_RESTRICT visitor) override;
+
+  Status Set(size_t xsize, size_t ysize);
+
+  size_t xsize() const;
+  size_t ysize() const {
+    return small_ ? ((ysize_div8_minus_1_ + 1) * 8) : ysize_;
+  }
+
+ private:
+  bool small_;  // xsize and ysize <= 256 and divisible by 8.
+
+  uint32_t ysize_div8_minus_1_;
+  uint32_t ysize_;
+
+  uint32_t ratio_;
+  uint32_t xsize_div8_minus_1_;
+  uint32_t xsize_;
+};
+
+// (Similar to SizeHeader but different encoding because previews are smaller)
+class PreviewHeader : public Fields {
+ public:
+  PreviewHeader();
+  JXL_FIELDS_NAME(PreviewHeader)
+
+  Status VisitFields(Visitor* JXL_RESTRICT visitor) override;
+
+  Status Set(size_t xsize, size_t ysize);
+
+  size_t xsize() const;
+  size_t ysize() const { return div8_ ? (ysize_div8_ * 8) : ysize_; }
+
+ private:
+  bool div8_;  // xsize and ysize divisible by 8.
+
+  uint32_t ysize_div8_;
+  uint32_t ysize_;
+
+  uint32_t ratio_;
+  uint32_t xsize_div8_;
+  uint32_t xsize_;
+};
+
+struct AnimationHeader : public Fields {
+  AnimationHeader();
+  JXL_FIELDS_NAME(AnimationHeader)
+
+  Status VisitFields(Visitor* JXL_RESTRICT visitor) override;
+
+  // Ticks per second (expressed as rational number to support NTSC)
+  uint32_t tps_numerator;
+  uint32_t tps_denominator;
+
+  uint32_t num_loops;  // 0 means to repeat infinitely.
+
+  bool have_timecodes;
+};
+
+Status ReadSizeHeader(BitReader* JXL_RESTRICT reader,
+                      SizeHeader* JXL_RESTRICT size);
+
+Status WriteSizeHeader(const SizeHeader& size, BitWriter* JXL_RESTRICT writer,
+                       size_t layer, AuxOut* aux_out);
+
+}  // namespace jxl
+
+#endif  // LIB_JXL_HEADERS_H_