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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #include <algorithm> |
| 6 |
| 7 #include "base/logging.h" |
| 8 #include "media/filters/h264_parser.h" |
| 9 #include "media/video/h264_poc.h" |
| 10 |
| 11 namespace media { |
| 12 |
| 13 H264POC::H264POC() { |
| 14 Reset(); |
| 15 } |
| 16 |
| 17 H264POC::~H264POC() { |
| 18 } |
| 19 |
| 20 void H264POC::Reset() { |
| 21 // It shouldn't be necessary to reset these values, but doing so will improve |
| 22 // reproducibility for buggy streams. |
| 23 ref_pic_order_cnt_msb_ = 0; |
| 24 ref_pic_order_cnt_lsb_ = 0; |
| 25 prev_frame_num_ = 0; |
| 26 prev_frame_num_offset_ = 0; |
| 27 } |
| 28 |
| 29 // Check if a slice includes memory management control operation 5, which |
| 30 // results in some |pic_order_cnt| state being cleared. |
| 31 static bool HasMMCO5(const media::H264SliceHeader& slice_hdr) { |
| 32 // Require that the frame actually has memory management control operations. |
| 33 if (slice_hdr.nal_ref_idc == 0 || |
| 34 slice_hdr.idr_pic_flag || |
| 35 !slice_hdr.adaptive_ref_pic_marking_mode_flag) { |
| 36 return false; |
| 37 } |
| 38 |
| 39 for (size_t i = 0; i < arraysize(slice_hdr.ref_pic_marking); i++) { |
| 40 int32_t op = slice_hdr.ref_pic_marking[i].memory_mgmnt_control_operation; |
| 41 if (op == 5) |
| 42 return true; |
| 43 |
| 44 // Stop at the end of the list. |
| 45 if (op == 0) |
| 46 return false; |
| 47 } |
| 48 |
| 49 // Should not get here, the list is always zero terminated. |
| 50 return false; |
| 51 } |
| 52 |
| 53 bool H264POC::ComputePicOrderCnt( |
| 54 const H264SPS* sps, |
| 55 const H264SliceHeader& slice_hdr, |
| 56 int32_t *pic_order_cnt) { |
| 57 if (slice_hdr.field_pic_flag) { |
| 58 DLOG(ERROR) << "Interlaced frames are not supported"; |
| 59 return false; |
| 60 } |
| 61 |
| 62 // TODO(sandersd): Handle |gaps_in_frame_num_value|. |
| 63 if (prev_frame_num_ > 0 && prev_frame_num_ < slice_hdr.frame_num - 1) { |
| 64 DLOG(ERROR) << "Gaps in frame_num are not supported"; |
| 65 return false; |
| 66 } |
| 67 |
| 68 bool mmco5 = HasMMCO5(slice_hdr); |
| 69 int32_t max_frame_num = 1 << (sps->log2_max_frame_num_minus4 + 4); |
| 70 int32_t max_pic_order_cnt_lsb = |
| 71 1 << (sps->log2_max_pic_order_cnt_lsb_minus4 + 4); |
| 72 |
| 73 // Based on T-REC-H.264 8.2.1, "Decoding process for picture order |
| 74 // count", available from http://www.itu.int/rec/T-REC-H.264. |
| 75 // |
| 76 // Reorganized slightly from spec pseudocode to handle MMCO5 when storing |
| 77 // state instead of when loading it. |
| 78 switch (sps->pic_order_cnt_type) { |
| 79 case 0: { |
| 80 int32_t prev_pic_order_cnt_msb = ref_pic_order_cnt_msb_; |
| 81 int32_t prev_pic_order_cnt_lsb = ref_pic_order_cnt_lsb_; |
| 82 |
| 83 // For an IDR picture, clear the state. |
| 84 if (slice_hdr.idr_pic_flag) { |
| 85 prev_pic_order_cnt_msb = 0; |
| 86 prev_pic_order_cnt_lsb = 0; |
| 87 } |
| 88 |
| 89 // 8-3. Derive |pic_order_cnt_msb|, accounting for wrapping which is |
| 90 // detected when |pic_order_cnt_lsb| increases or decreases by at |
| 91 // least half of its maximum. |
| 92 int32_t pic_order_cnt_msb; |
| 93 if ((slice_hdr.pic_order_cnt_lsb < prev_pic_order_cnt_lsb) && |
| 94 (prev_pic_order_cnt_lsb - slice_hdr.pic_order_cnt_lsb >= |
| 95 max_pic_order_cnt_lsb / 2)) { |
| 96 pic_order_cnt_msb = prev_pic_order_cnt_msb + max_pic_order_cnt_lsb; |
| 97 } else if ((slice_hdr.pic_order_cnt_lsb > prev_pic_order_cnt_lsb) && |
| 98 (slice_hdr.pic_order_cnt_lsb - prev_pic_order_cnt_lsb > |
| 99 max_pic_order_cnt_lsb / 2)) { |
| 100 pic_order_cnt_msb = prev_pic_order_cnt_msb - max_pic_order_cnt_lsb; |
| 101 } else { |
| 102 pic_order_cnt_msb = prev_pic_order_cnt_msb; |
| 103 } |
| 104 |
| 105 // 8-4, 8-5. Derive |top_field_order_count| and |bottom_field_order_cnt| |
| 106 // (assuming no interlacing). |
| 107 int32_t top_foc = pic_order_cnt_msb + slice_hdr.pic_order_cnt_lsb; |
| 108 int32_t bottom_foc = top_foc + slice_hdr.delta_pic_order_cnt_bottom; |
| 109 *pic_order_cnt = std::min(top_foc, bottom_foc); |
| 110 |
| 111 // Store state. |
| 112 prev_frame_num_ = slice_hdr.frame_num; |
| 113 if (slice_hdr.nal_ref_idc != 0) { |
| 114 if (mmco5) { |
| 115 ref_pic_order_cnt_msb_ = 0; |
| 116 ref_pic_order_cnt_lsb_ = top_foc; |
| 117 } else { |
| 118 ref_pic_order_cnt_msb_ = pic_order_cnt_msb; |
| 119 ref_pic_order_cnt_lsb_ = slice_hdr.pic_order_cnt_lsb; |
| 120 } |
| 121 } |
| 122 |
| 123 break; |
| 124 } |
| 125 |
| 126 case 1: { |
| 127 // 8-6. Derive |frame_num_offset|. |
| 128 int32_t frame_num_offset; |
| 129 if (slice_hdr.idr_pic_flag) |
| 130 frame_num_offset = 0; |
| 131 else if (prev_frame_num_ > slice_hdr.frame_num) |
| 132 frame_num_offset = prev_frame_num_offset_ + max_frame_num; |
| 133 else |
| 134 frame_num_offset = prev_frame_num_offset_; |
| 135 |
| 136 // 8-7. Derive |abs_frame_num|. |
| 137 int32_t abs_frame_num; |
| 138 if (sps->num_ref_frames_in_pic_order_cnt_cycle != 0) |
| 139 abs_frame_num = frame_num_offset + slice_hdr.frame_num; |
| 140 else |
| 141 abs_frame_num = 0; |
| 142 |
| 143 if (slice_hdr.nal_ref_idc == 0 && abs_frame_num > 0) |
| 144 abs_frame_num--; |
| 145 |
| 146 // 8-9. Derive |expected_pic_order_cnt| (the |pic_order_cnt| indicated |
| 147 // by the cycle described in the SPS). |
| 148 int32_t expected_pic_order_cnt = 0; |
| 149 if (abs_frame_num > 0) { |
| 150 // 8-8. Derive pic_order_cnt_cycle_cnt and |
| 151 // frame_num_in_pic_order_cnt_cycle. |
| 152 // Moved inside 8-9 to avoid division when this check is not done. |
| 153 if (sps->num_ref_frames_in_pic_order_cnt_cycle == 0) { |
| 154 DLOG(ERROR) << "Invalid num_ref_frames_in_pic_order_cnt_cycle"; |
| 155 return false; |
| 156 } |
| 157 |
| 158 // H264Parser checks that num_ref_frames_in_pic_order_cnt_cycle < 255. |
| 159 int32_t pic_order_cnt_cycle_cnt = |
| 160 (abs_frame_num - 1) / sps->num_ref_frames_in_pic_order_cnt_cycle; |
| 161 int32_t frame_num_in_pic_order_cnt_cycle = |
| 162 (abs_frame_num - 1) % sps->num_ref_frames_in_pic_order_cnt_cycle; |
| 163 |
| 164 // 8-9 continued. |
| 165 expected_pic_order_cnt = pic_order_cnt_cycle_cnt * |
| 166 sps->expected_delta_per_pic_order_cnt_cycle; |
| 167 for (int32_t i = 0; i <= frame_num_in_pic_order_cnt_cycle; i++) |
| 168 expected_pic_order_cnt += sps->offset_for_ref_frame[i]; |
| 169 } |
| 170 if (slice_hdr.nal_ref_idc == 0) |
| 171 expected_pic_order_cnt += sps->offset_for_non_ref_pic; |
| 172 |
| 173 // 8-10. Derive |top_field_order_cnt| and |bottom_field_order_cnt| |
| 174 // (assuming no interlacing). |
| 175 int32_t top_foc = expected_pic_order_cnt + |
| 176 slice_hdr.delta_pic_order_cnt[0]; |
| 177 int32_t bottom_foc = top_foc + sps->offset_for_top_to_bottom_field + |
| 178 slice_hdr.delta_pic_order_cnt[1]; |
| 179 *pic_order_cnt = std::min(top_foc, bottom_foc); |
| 180 |
| 181 // Store state. |
| 182 prev_frame_num_ = slice_hdr.frame_num; |
| 183 prev_frame_num_offset_ = frame_num_offset; |
| 184 if (mmco5) |
| 185 prev_frame_num_offset_ = 0; |
| 186 |
| 187 break; |
| 188 } |
| 189 |
| 190 case 2: { |
| 191 // 8-11. Derive |frame_num_offset|. |
| 192 int32_t frame_num_offset; |
| 193 if (slice_hdr.idr_pic_flag) |
| 194 frame_num_offset = 0; |
| 195 else if (prev_frame_num_ > slice_hdr.frame_num) |
| 196 frame_num_offset = prev_frame_num_offset_ + max_frame_num; |
| 197 else |
| 198 frame_num_offset = prev_frame_num_offset_; |
| 199 |
| 200 // 8-12, 8-13. Derive |temp_pic_order_count| (it's always the |
| 201 // |pic_order_cnt|, regardless of interlacing). |
| 202 if (slice_hdr.idr_pic_flag) |
| 203 *pic_order_cnt = 0; |
| 204 else if (slice_hdr.nal_ref_idc == 0) |
| 205 *pic_order_cnt = 2 * (frame_num_offset + slice_hdr.frame_num) - 1; |
| 206 else |
| 207 *pic_order_cnt = 2 * (frame_num_offset + slice_hdr.frame_num); |
| 208 |
| 209 // Store state. |
| 210 prev_frame_num_ = slice_hdr.frame_num; |
| 211 prev_frame_num_offset_ = frame_num_offset; |
| 212 if (mmco5) |
| 213 prev_frame_num_offset_ = 0; |
| 214 |
| 215 break; |
| 216 } |
| 217 |
| 218 default: |
| 219 DLOG(ERROR) << "Invalid pic_order_cnt_type: " << sps->pic_order_cnt_type; |
| 220 return false; |
| 221 } |
| 222 |
| 223 return true; |
| 224 } |
| 225 |
| 226 } // namespace media |
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