15d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles)// Copyright 2014 The Chromium Authors. All rights reserved. 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// found in the LICENSE file. 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "base/logging.h" 65d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles)#include "media/filters/h264_bit_reader.h" 75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 85d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles)namespace media { 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)H264BitReader::H264BitReader() 115d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles) : data_(NULL), 125d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles) bytes_left_(0), 135d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles) curr_byte_(0), 145d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles) num_remaining_bits_in_curr_byte_(0), 155d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles) prev_two_bytes_(0), 165d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles) emulation_prevention_bytes_(0) {} 175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)H264BitReader::~H264BitReader() {} 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)bool H264BitReader::Initialize(const uint8* data, off_t size) { 215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DCHECK(data); 225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (size < 1) 245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) data_ = data; 275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bytes_left_ = size; 285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) num_remaining_bits_in_curr_byte_ = 0; 295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Initially set to 0xffff to accept all initial two-byte sequences. 305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) prev_two_bytes_ = 0xffff; 314e180b6a0b4720a9b8e9e959a882386f690f08ffTorne (Richard Coles) emulation_prevention_bytes_ = 0; 325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)bool H264BitReader::UpdateCurrByte() { 375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (bytes_left_ < 1) 385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Emulation prevention three-byte detection. 415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If a sequence of 0x000003 is found, skip (ignore) the last byte (0x03). 425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (*data_ == 0x03 && (prev_two_bytes_ & 0xffff) == 0) { 435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Detected 0x000003, skip last byte. 445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ++data_; 455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) --bytes_left_; 464e180b6a0b4720a9b8e9e959a882386f690f08ffTorne (Richard Coles) ++emulation_prevention_bytes_; 475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Need another full three bytes before we can detect the sequence again. 485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) prev_two_bytes_ = 0xffff; 495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (bytes_left_ < 1) 515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Load a new byte and advance pointers. 555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) curr_byte_ = *data_++ & 0xff; 565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) --bytes_left_; 575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) num_remaining_bits_in_curr_byte_ = 8; 585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) prev_two_bytes_ = (prev_two_bytes_ << 8) | curr_byte_; 605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Read |num_bits| (1 to 31 inclusive) from the stream and return them 655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// in |out|, with first bit in the stream as MSB in |out| at position 665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// (|num_bits| - 1). 675d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles)bool H264BitReader::ReadBits(int num_bits, int* out) { 685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) int bits_left = num_bits; 695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *out = 0; 705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DCHECK(num_bits <= 31); 715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) while (num_remaining_bits_in_curr_byte_ < bits_left) { 735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Take all that's left in current byte, shift to make space for the rest. 745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *out |= (curr_byte_ << (bits_left - num_remaining_bits_in_curr_byte_)); 755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bits_left -= num_remaining_bits_in_curr_byte_; 765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!UpdateCurrByte()) 785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *out |= (curr_byte_ >> (num_remaining_bits_in_curr_byte_ - bits_left)); 825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *out &= ((1 << num_bits) - 1); 835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) num_remaining_bits_in_curr_byte_ -= bits_left; 845821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)off_t H264BitReader::NumBitsLeft() { 895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return (num_remaining_bits_in_curr_byte_ + bytes_left_ * 8); 905821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 915821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 925821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)bool H264BitReader::HasMoreRBSPData() { 935821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Make sure we have more bits, if we are at 0 bits in current byte 945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // and updating current byte fails, we don't have more data anyway. 955821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (num_remaining_bits_in_curr_byte_ == 0 && !UpdateCurrByte()) 965d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles) return false; 975821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 985821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // On last byte? 995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (bytes_left_) 1005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 1015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Last byte, look for stop bit; 1035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // We have more RBSP data if the last non-zero bit we find is not the 1045821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // first available bit. 1055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return (curr_byte_ & 1065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ((1 << (num_remaining_bits_in_curr_byte_ - 1)) - 1)) != 0; 1075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 1085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1095d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles)size_t H264BitReader::NumEmulationPreventionBytesRead() { 1104e180b6a0b4720a9b8e9e959a882386f690f08ffTorne (Richard Coles) return emulation_prevention_bytes_; 1114e180b6a0b4720a9b8e9e959a882386f690f08ffTorne (Richard Coles)} 1124e180b6a0b4720a9b8e9e959a882386f690f08ffTorne (Richard Coles) 1135d1f7b1de12d16ceb2c938c56701a3e8bfa558f7Torne (Richard Coles)} // namespace media 114