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// Copyright 2012 The Cobalt Authors. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include "base/basictypes.h"
namespace cobalt {
namespace media {
// ISO 14496-10 describes a byte encoding format for NALUs (network abstraction
// layer units) and rules to convert it into a RBSP stream, which is the format
// that some other atoms are defined. This class takes a non-owning reference
// to a buffer and extract various types from the stream while silently
// consuming the extra encoding bytes and advancing a bit stream pointer.
class RBSPStream {
// NON-OWNING pointer to buffer. It is assumed the client will dispose of
// this buffer.
RBSPStream(const uint8* nalu_buffer, size_t nalu_buffer_size);
// all Read/Skip methods return the value by reference and return true
// on success, false on read error/EOB. Once the object has returned
// false the consistency of the data is not guaranteed.
// read unsigned Exp-Golomb coded integer, ISO 14496-10 Section 9.1
bool ReadUEV(uint32* uev_out);
// read signed Exp-Golomb coded integer, ISO 14496-10 Section 9.1
bool ReadSEV(int32* sev_out);
// read and return up to 32 bits, filling from the right, meaning that
// ReadBits(17) on a stream of all 1s would return 0x01ffff
bool ReadBits(size_t bits, uint32* bits_out);
bool ReadByte(uint8* byte_out) { return ReadRBSPByte(byte_out); }
bool ReadBit(uint8* bit_out) { return ReadRBSPBit(bit_out); }
// jump over bytes in the RBSP stream
bool SkipBytes(size_t bytes);
// jump over bits in the RBSP stream
bool SkipBits(size_t bits);
// advance by one byte through the NALU buffer, respecting the encoding of
// 00 00 03 => 00 00. Updates the state of current_nalu_byte_ to the new
// value.
// returns fale if we have moved past the end of the buffer.
bool ConsumeNALUByte();
// return single bit in the LSb from the RBSP stream. Bits are read from MSb
// to LSb in the stream.
bool ReadRBSPBit(uint8* bit_out);
bool ReadRBSPByte(uint8* byte_out);
const uint8* nalu_buffer_;
size_t nalu_buffer_size_;
size_t nalu_buffer_byte_offset_;
uint8 current_nalu_byte_;
int number_consecutive_zeros_;
// location of rbsp bit cursor within current_nalu_byte_
size_t rbsp_bit_offset_;
} // namespace media
} // namespace cobalt