Add JPEG parser for JPEG decode acceleration

media/filters/jpeg_parser.h

+// Copyright 2014 The Chromium Authors. All rights reserved.

[xhwang, 2015/01/12 18:08:58]

2015?

[kcwu, 2015/01/13 14:57:01]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+#ifndef MEDIA_FILTERS_JPEG_PARSER_H_
+#define MEDIA_FILTERS_JPEG_PARSER_H_
+
+#include <stdint.h>
+#include "base/macros.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+static const size_t kJpegMaxHuffmanTableNum_baseline = 2;

[xhwang, 2015/01/12 18:08:58]

s/_baseline/Baseline

[xhwang, 2015/01/12 18:08:58]

static not needed for consts.

[kcwu, 2015/01/13 14:57:00]

Done.

[kcwu, 2015/01/13 14:57:01]

Done.

+static const size_t kJpegMaxComponents = 4;
+static const size_t kJpegMaxQuantizationTableNum = 4;
+
+// Parsing result of JPEG DHT marker.
+struct JpegHuffmanTable {
+  bool valid;
+  uint8_t code_length[16];
+  uint8_t code_value[256];
+};
+
+// Parsing result of JPEG DQT marker.
+struct JpegQuantizationTable {
+  bool valid;
+  uint8_t value[64];  // baseline only supports 8 bits quantization table
+};
+
+// Parsing result of a JPEG component.
+struct JpegComponent {
+  uint8_t id;
+  uint8_t horizontal_sampling_factor;
+  uint8_t vertical_sampling_factor;
+  uint8_t quantization_table_selector;
+};
+
+// Parsing result of JPEG SOS marker.
+struct JpegScan {
+  uint8_t num_components;
+  struct Component {
+    uint8_t component_selector;
+    uint8_t dc_selector;
+    uint8_t ac_selector;
+  } components[kJpegMaxComponents];
+  const char* data;
+  size_t data_size;
+};
+
+struct JpegParseResult {
+  uint16_t visible_width;
+  uint16_t visible_height;
+  uint8_t num_components;
+  JpegComponent components[kJpegMaxComponents];
+  JpegHuffmanTable dc_table[kJpegMaxHuffmanTableNum_baseline];
+  JpegHuffmanTable ac_table[kJpegMaxHuffmanTableNum_baseline];
+  JpegQuantizationTable q_table[kJpegMaxQuantizationTableNum];
+  uint16_t restart_interval;
+  JpegScan scan;
+};
+
+// JpegParser parses JPEG header. It's not a full featured JPEG parser

[xhwang, 2015/01/12 18:08:58]

In this case, how about s/JpegParser/JpegHeaderParser?

[kcwu, 2015/01/13 14:57:00]

Now I named the function as ParseJpegPicture. Not naming it as ParseJpegHeader
because for typical usage, the input is whole JPEG picture, not header only.

+// implememtation. It only parses JPEG baseline sequential process.  For
+// explanations of each struct and its members, see JPEG specification at
+// http://www.w3.org/Graphics/JPEG/itu-t81.pdf.
+class MEDIA_EXPORT JpegParser {

[xhwang, 2015/01/12 18:08:58]

It seems we only need a Parse() function which is static. If so, you don't need
to use a class, you can just have a function declared here.

[kcwu, 2015/01/13 14:57:00]

Done.

+ public:
+  // Parses JPEG picture in |buffer| with |length|. Returns true iff header is
+  // valid and JPEG baseline sequential process is present. If parsed
+  // successfully, |result| is the parsed result.
+  static bool Parse(const uint8_t* buffer,
+                    size_t length,
+                    JpegParseResult* result);
+
+ private:
+  static bool ParseSOF(const char* buffer,

[xhwang, 2015/01/12 18:08:58]

Can you hide all these functions in the .cc file?

[kcwu, 2015/01/13 14:57:01]

Done.

+                       size_t length,
+                       JpegParseResult* result);
+  static bool ParseDQT(const char* buffer,
+                       size_t length,
+                       JpegParseResult* result);
+  static bool ParseDHT(const char* buffer,
+                       size_t length,
+                       JpegParseResult* result);
+  static bool ParseDRI(const char* buffer,
+                       size_t length,
+                       JpegParseResult* result);
+  static bool ParseSOS(const char* buffer,
+                       size_t length,
+                       JpegParseResult* result);
+  static bool ParseSOI(const char* buffer,
+                       size_t length,
+                       JpegParseResult* result);
+
+  DISALLOW_COPY_AND_ASSIGN(JpegParser);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_JPEG_PARSER_H_