sps_vui_rewriter.h

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/*

 *  Copyright (c) 2016 The WebRTC 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 in the root of the source

 *  tree. An additional intellectual property rights grant can be found

 *  in the file PATENTS.  All contributing project authors may

 *  be found in the AUTHORS file in the root of the source tree.

*/

#ifndef COMMON_VIDEO_H264_SPS_VUI_REWRITER_H_

#define COMMON_VIDEO_H264_SPS_VUI_REWRITER_H_

#include <stddef.h>

#include <stdint.h>

#include <optional>

#include "api/video/color_space.h"

#include "common_video/h264/sps_parser.h"

#include "rtc_base/buffer.h"

namespace webrtc {

// A class that can parse an SPS+VUI and if necessary creates a copy with

// updated parameters.

// The rewriter disables frame buffering. This should force decoders to deliver

// decoded frame immediately and, thus, reduce latency.

// The rewriter updates video signal type parameters if external parameters are

// provided.

class SpsVuiRewriter : private SpsParser {

 public:

  enum class ParseResult { kFailure, kVuiOk, kVuiRewritten };

  enum class Direction { kIncoming, kOutgoing };

  // Parses an SPS block and if necessary copies it and rewrites the VUI.

  // Returns kFailure on failure, kParseOk if parsing succeeded and no update

  // was necessary and kParsedAndModified if an updated copy of buffer was

  // written to destination. destination may be populated with some data even if

  // no rewrite was necessary, but the end offset should remain unchanged.

  // Unless parsing fails, the sps parameter will be populated with the parsed

  // SPS state. This function assumes that any previous headers

  // (NALU start, type, Stap-A, etc) have already been parsed and that RBSP

  // decoding has been performed.

  static ParseResult ParseAndRewriteSps(rtc::ArrayView<const uint8_t> buffer,

                                        std::optional<SpsParser::SpsState>* sps,

                                        const ColorSpace* color_space,

                                        rtc::Buffer* destination,

                                        Direction Direction);

  // Parses NAL units from `buffer`, strips AUD blocks and rewrites VUI in SPS

  // blocks if necessary.

  static rtc::Buffer ParseOutgoingBitstreamAndRewrite(

      rtc::ArrayView<const uint8_t> buffer,

      const ColorSpace* color_space);

 private:

  static ParseResult ParseAndRewriteSps(rtc::ArrayView<const uint8_t> buffer,

                                        std::optional<SpsParser::SpsState>* sps,

                                        const ColorSpace* color_space,

                                        rtc::Buffer* destination);

  static void UpdateStats(ParseResult result, Direction direction);

};

}  // namespace webrtc

#endif  // COMMON_VIDEO_H264_SPS_VUI_REWRITER_H_