/* * 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. */ #include "webrtc/common_video/h264/pps_parser.h" #include "webrtc/common_video/h264/h264_common.h" #include "webrtc/base/bitbuffer.h" #include "webrtc/base/buffer.h" #include "webrtc/base/logging.h" #define RETURN_EMPTY_ON_FAIL(x) \ if (!(x)) { \ return rtc::Optional(); \ } namespace webrtc { // General note: this is based off the 02/2014 version of the H.264 standard. // You can find it on this page: // http://www.itu.int/rec/T-REC-H.264 rtc::Optional PpsParser::ParsePps(const uint8_t* data, size_t length) { // First, parse out rbsp, which is basically the source buffer minus emulation // bytes (the last byte of a 0x00 0x00 0x03 sequence). RBSP is defined in // section 7.3.1 of the H.264 standard. std::unique_ptr unpacked_buffer = H264::ParseRbsp(data, length); rtc::BitBuffer bit_buffer(unpacked_buffer->data(), unpacked_buffer->size()); return ParseInternal(&bit_buffer); } rtc::Optional PpsParser::ParseInternal( rtc::BitBuffer* bit_buffer) { PpsState pps; uint32_t bits_tmp; uint32_t golomb_ignored; // pic_parameter_set_id: ue(v) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored)); // seq_parameter_set_id: ue(v) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored)); // entropy_coding_mode_flag: u(1) uint32_t entropy_coding_mode_flag; RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&entropy_coding_mode_flag, 1)); // TODO(pbos): Implement CABAC support if spotted in the wild. RTC_CHECK(entropy_coding_mode_flag == 0) << "Don't know how to parse CABAC streams."; // bottom_field_pic_order_in_frame_present_flag: u(1) uint32_t bottom_field_pic_order_in_frame_present_flag; RETURN_EMPTY_ON_FAIL( bit_buffer->ReadBits(&bottom_field_pic_order_in_frame_present_flag, 1)); pps.bottom_field_pic_order_in_frame_present_flag = bottom_field_pic_order_in_frame_present_flag != 0; // num_slice_groups_minus1: ue(v) uint32_t num_slice_groups_minus1; RETURN_EMPTY_ON_FAIL( bit_buffer->ReadExponentialGolomb(&num_slice_groups_minus1)); if (num_slice_groups_minus1 > 0) { uint32_t slice_group_map_type; // slice_group_map_type: ue(v) RETURN_EMPTY_ON_FAIL( bit_buffer->ReadExponentialGolomb(&slice_group_map_type)); if (slice_group_map_type == 0) { for (uint32_t i_group = 0; i_group <= num_slice_groups_minus1; ++i_group) { // run_length_minus1[iGroup]: ue(v) RETURN_EMPTY_ON_FAIL( bit_buffer->ReadExponentialGolomb(&golomb_ignored)); } } else if (slice_group_map_type == 1) { // TODO(sprang): Implement support for dispersed slice group map type. // See 8.2.2.2 Specification for dispersed slice group map type. } else if (slice_group_map_type == 2) { for (uint32_t i_group = 0; i_group <= num_slice_groups_minus1; ++i_group) { // top_left[iGroup]: ue(v) RETURN_EMPTY_ON_FAIL( bit_buffer->ReadExponentialGolomb(&golomb_ignored)); // bottom_right[iGroup]: ue(v) RETURN_EMPTY_ON_FAIL( bit_buffer->ReadExponentialGolomb(&golomb_ignored)); } } else if (slice_group_map_type == 3 || slice_group_map_type == 4 || slice_group_map_type == 5) { // slice_group_change_direction_flag: u(1) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&bits_tmp, 1)); // slice_group_change_rate_minus1: ue(v) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored)); } else if (slice_group_map_type == 6) { // pic_size_in_map_units_minus1: ue(v) uint32_t pic_size_in_map_units_minus1; RETURN_EMPTY_ON_FAIL( bit_buffer->ReadExponentialGolomb(&pic_size_in_map_units_minus1)); uint32_t slice_group_id_bits = 0; uint32_t num_slice_groups = num_slice_groups_minus1 + 1; // If num_slice_groups is not a power of two an additional bit is required // to account for the ceil() of log2() below. if ((num_slice_groups & (num_slice_groups - 1)) != 0) ++slice_group_id_bits; while (num_slice_groups > 0) { num_slice_groups >>= 1; ++slice_group_id_bits; } for (uint32_t i = 0; i <= pic_size_in_map_units_minus1; i++) { // slice_group_id[i]: u(v) // Represented by ceil(log2(num_slice_groups_minus1 + 1)) bits. RETURN_EMPTY_ON_FAIL( bit_buffer->ReadBits(&bits_tmp, slice_group_id_bits)); } } } // num_ref_idx_l0_default_active_minus1: ue(v) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored)); // num_ref_idx_l1_default_active_minus1: ue(v) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored)); // weighted_pred_flag: u(1) uint32_t weighted_pred_flag; RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&weighted_pred_flag, 1)); pps.weighted_pred_flag = weighted_pred_flag != 0; // weighted_bipred_idc: u(2) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&pps.weighted_bipred_idc, 2)); // pic_init_qp_minus26: se(v) RETURN_EMPTY_ON_FAIL( bit_buffer->ReadSignedExponentialGolomb(&pps.pic_init_qp_minus26)); // pic_init_qs_minus26: se(v) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored)); // chroma_qp_index_offset: se(v) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored)); // deblocking_filter_control_present_flag: u(1) // constrained_intra_pred_flag: u(1) RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&bits_tmp, 2)); // redundant_pic_cnt_present_flag: u(1) RETURN_EMPTY_ON_FAIL( bit_buffer->ReadBits(&pps.redundant_pic_cnt_present_flag, 1)); return rtc::Optional(pps); } } // namespace webrtc