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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
| 4 | 4 |
| 5 #include "content/common/gpu/media/h264_bit_reader.h" | |
| 6 #include "base/logging.h" | 5 #include "base/logging.h" |
| 6 #include "media/filters/h264_bit_reader.h" |
| 7 | 7 |
| 8 namespace content { | 8 namespace media { |
| 9 | 9 |
| 10 H264BitReader::H264BitReader() | 10 H264BitReader::H264BitReader() |
| 11 : data_(NULL), bytes_left_(0), curr_byte_(0), | 11 : data_(NULL), |
| 12 num_remaining_bits_in_curr_byte_(0), prev_two_bytes_(0), | 12 bytes_left_(0), |
| 13 emulation_prevention_bytes_(0) { | 13 curr_byte_(0), |
| 14 } | 14 num_remaining_bits_in_curr_byte_(0), |
| 15 prev_two_bytes_(0), |
| 16 emulation_prevention_bytes_(0) {} |
| 15 | 17 |
| 16 H264BitReader::~H264BitReader() {} | 18 H264BitReader::~H264BitReader() {} |
| 17 | 19 |
| 18 bool H264BitReader::Initialize(const uint8* data, off_t size) { | 20 bool H264BitReader::Initialize(const uint8* data, off_t size) { |
| 19 DCHECK(data); | 21 DCHECK(data); |
| 20 | 22 |
| 21 if (size < 1) | 23 if (size < 1) |
| 22 return false; | 24 return false; |
| 23 | 25 |
| 24 data_ = data; | 26 data_ = data; |
| (...skipping 30 matching lines...) Expand all Loading... |
| 55 num_remaining_bits_in_curr_byte_ = 8; | 57 num_remaining_bits_in_curr_byte_ = 8; |
| 56 | 58 |
| 57 prev_two_bytes_ = (prev_two_bytes_ << 8) | curr_byte_; | 59 prev_two_bytes_ = (prev_two_bytes_ << 8) | curr_byte_; |
| 58 | 60 |
| 59 return true; | 61 return true; |
| 60 } | 62 } |
| 61 | 63 |
| 62 // Read |num_bits| (1 to 31 inclusive) from the stream and return them | 64 // Read |num_bits| (1 to 31 inclusive) from the stream and return them |
| 63 // in |out|, with first bit in the stream as MSB in |out| at position | 65 // in |out|, with first bit in the stream as MSB in |out| at position |
| 64 // (|num_bits| - 1). | 66 // (|num_bits| - 1). |
| 65 bool H264BitReader::ReadBits(int num_bits, int *out) { | 67 bool H264BitReader::ReadBits(int num_bits, int* out) { |
| 66 int bits_left = num_bits; | 68 int bits_left = num_bits; |
| 67 *out = 0; | 69 *out = 0; |
| 68 DCHECK(num_bits <= 31); | 70 DCHECK(num_bits <= 31); |
| 69 | 71 |
| 70 while (num_remaining_bits_in_curr_byte_ < bits_left) { | 72 while (num_remaining_bits_in_curr_byte_ < bits_left) { |
| 71 // Take all that's left in current byte, shift to make space for the rest. | 73 // Take all that's left in current byte, shift to make space for the rest. |
| 72 *out |= (curr_byte_ << (bits_left - num_remaining_bits_in_curr_byte_)); | 74 *out |= (curr_byte_ << (bits_left - num_remaining_bits_in_curr_byte_)); |
| 73 bits_left -= num_remaining_bits_in_curr_byte_; | 75 bits_left -= num_remaining_bits_in_curr_byte_; |
| 74 | 76 |
| 75 if (!UpdateCurrByte()) | 77 if (!UpdateCurrByte()) |
| 76 return false; | 78 return false; |
| 77 } | 79 } |
| 78 | 80 |
| 79 *out |= (curr_byte_ >> (num_remaining_bits_in_curr_byte_ - bits_left)); | 81 *out |= (curr_byte_ >> (num_remaining_bits_in_curr_byte_ - bits_left)); |
| 80 *out &= ((1 << num_bits) - 1); | 82 *out &= ((1 << num_bits) - 1); |
| 81 num_remaining_bits_in_curr_byte_ -= bits_left; | 83 num_remaining_bits_in_curr_byte_ -= bits_left; |
| 82 | 84 |
| 83 return true; | 85 return true; |
| 84 } | 86 } |
| 85 | 87 |
| 86 off_t H264BitReader::NumBitsLeft() { | 88 off_t H264BitReader::NumBitsLeft() { |
| 87 return (num_remaining_bits_in_curr_byte_ + bytes_left_ * 8); | 89 return (num_remaining_bits_in_curr_byte_ + bytes_left_ * 8); |
| 88 } | 90 } |
| 89 | 91 |
| 90 bool H264BitReader::HasMoreRBSPData() { | 92 bool H264BitReader::HasMoreRBSPData() { |
| 91 // Make sure we have more bits, if we are at 0 bits in current byte | 93 // Make sure we have more bits, if we are at 0 bits in current byte |
| 92 // and updating current byte fails, we don't have more data anyway. | 94 // and updating current byte fails, we don't have more data anyway. |
| 93 if (num_remaining_bits_in_curr_byte_ == 0 && !UpdateCurrByte()) | 95 if (num_remaining_bits_in_curr_byte_ == 0 && !UpdateCurrByte()) |
| 94 return false; | 96 return false; |
| 95 | 97 |
| 96 // On last byte? | 98 // On last byte? |
| 97 if (bytes_left_) | 99 if (bytes_left_) |
| 98 return true; | 100 return true; |
| 99 | 101 |
| 100 // Last byte, look for stop bit; | 102 // Last byte, look for stop bit; |
| 101 // We have more RBSP data if the last non-zero bit we find is not the | 103 // We have more RBSP data if the last non-zero bit we find is not the |
| 102 // first available bit. | 104 // first available bit. |
| 103 return (curr_byte_ & | 105 return (curr_byte_ & |
| 104 ((1 << (num_remaining_bits_in_curr_byte_ - 1)) - 1)) != 0; | 106 ((1 << (num_remaining_bits_in_curr_byte_ - 1)) - 1)) != 0; |
| 105 } | 107 } |
| 106 | 108 |
| 107 size_t H264BitReader::NumEmulationPreventionBytesRead() | 109 size_t H264BitReader::NumEmulationPreventionBytesRead() { |
| 108 { | |
| 109 return emulation_prevention_bytes_; | 110 return emulation_prevention_bytes_; |
| 110 } | 111 } |
| 111 | 112 |
| 112 } // namespace content | 113 } // namespace media |
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