149 lines
6.2 KiB
C++
149 lines
6.2 KiB
C++
/*
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* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/common_video/h264/pps_parser.h"
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#include "webrtc/common_video/h264/h264_common.h"
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#include "webrtc/base/bitbuffer.h"
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#include "webrtc/base/buffer.h"
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#include "webrtc/base/logging.h"
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#define RETURN_EMPTY_ON_FAIL(x) \
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if (!(x)) { \
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return rtc::Optional<PpsParser::PpsState>(); \
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}
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namespace webrtc {
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// General note: this is based off the 02/2014 version of the H.264 standard.
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// You can find it on this page:
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// http://www.itu.int/rec/T-REC-H.264
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rtc::Optional<PpsParser::PpsState> PpsParser::ParsePps(const uint8_t* data,
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size_t length) {
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// First, parse out rbsp, which is basically the source buffer minus emulation
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// bytes (the last byte of a 0x00 0x00 0x03 sequence). RBSP is defined in
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// section 7.3.1 of the H.264 standard.
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std::unique_ptr<rtc::Buffer> unpacked_buffer = H264::ParseRbsp(data, length);
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rtc::BitBuffer bit_buffer(unpacked_buffer->data(), unpacked_buffer->size());
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return ParseInternal(&bit_buffer);
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}
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rtc::Optional<PpsParser::PpsState> PpsParser::ParseInternal(
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rtc::BitBuffer* bit_buffer) {
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PpsState pps;
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uint32_t bits_tmp;
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uint32_t golomb_ignored;
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// pic_parameter_set_id: ue(v)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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// seq_parameter_set_id: ue(v)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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// entropy_coding_mode_flag: u(1)
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uint32_t entropy_coding_mode_flag;
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&entropy_coding_mode_flag, 1));
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// TODO(pbos): Implement CABAC support if spotted in the wild.
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RTC_CHECK(entropy_coding_mode_flag == 0)
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<< "Don't know how to parse CABAC streams.";
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// bottom_field_pic_order_in_frame_present_flag: u(1)
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uint32_t bottom_field_pic_order_in_frame_present_flag;
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadBits(&bottom_field_pic_order_in_frame_present_flag, 1));
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pps.bottom_field_pic_order_in_frame_present_flag =
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bottom_field_pic_order_in_frame_present_flag != 0;
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// num_slice_groups_minus1: ue(v)
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uint32_t num_slice_groups_minus1;
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadExponentialGolomb(&num_slice_groups_minus1));
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if (num_slice_groups_minus1 > 0) {
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uint32_t slice_group_map_type;
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// slice_group_map_type: ue(v)
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadExponentialGolomb(&slice_group_map_type));
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if (slice_group_map_type == 0) {
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for (uint32_t i_group = 0; i_group <= num_slice_groups_minus1;
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++i_group) {
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// run_length_minus1[iGroup]: ue(v)
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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}
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} else if (slice_group_map_type == 1) {
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// TODO(sprang): Implement support for dispersed slice group map type.
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// See 8.2.2.2 Specification for dispersed slice group map type.
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} else if (slice_group_map_type == 2) {
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for (uint32_t i_group = 0; i_group <= num_slice_groups_minus1;
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++i_group) {
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// top_left[iGroup]: ue(v)
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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// bottom_right[iGroup]: ue(v)
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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}
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} else if (slice_group_map_type == 3 || slice_group_map_type == 4 ||
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slice_group_map_type == 5) {
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// slice_group_change_direction_flag: u(1)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&bits_tmp, 1));
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// slice_group_change_rate_minus1: ue(v)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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} else if (slice_group_map_type == 6) {
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// pic_size_in_map_units_minus1: ue(v)
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uint32_t pic_size_in_map_units_minus1;
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadExponentialGolomb(&pic_size_in_map_units_minus1));
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uint32_t slice_group_id_bits = 0;
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uint32_t num_slice_groups = num_slice_groups_minus1 + 1;
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// If num_slice_groups is not a power of two an additional bit is required
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// to account for the ceil() of log2() below.
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if ((num_slice_groups & (num_slice_groups - 1)) != 0)
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++slice_group_id_bits;
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while (num_slice_groups > 0) {
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num_slice_groups >>= 1;
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++slice_group_id_bits;
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}
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for (uint32_t i = 0; i <= pic_size_in_map_units_minus1; i++) {
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// slice_group_id[i]: u(v)
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// Represented by ceil(log2(num_slice_groups_minus1 + 1)) bits.
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadBits(&bits_tmp, slice_group_id_bits));
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}
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}
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}
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// num_ref_idx_l0_default_active_minus1: ue(v)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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// num_ref_idx_l1_default_active_minus1: ue(v)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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// weighted_pred_flag: u(1)
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uint32_t weighted_pred_flag;
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&weighted_pred_flag, 1));
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pps.weighted_pred_flag = weighted_pred_flag != 0;
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// weighted_bipred_idc: u(2)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&pps.weighted_bipred_idc, 2));
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// pic_init_qp_minus26: se(v)
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadSignedExponentialGolomb(&pps.pic_init_qp_minus26));
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// pic_init_qs_minus26: se(v)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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// chroma_qp_index_offset: se(v)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadExponentialGolomb(&golomb_ignored));
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// deblocking_filter_control_present_flag: u(1)
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// constrained_intra_pred_flag: u(1)
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RETURN_EMPTY_ON_FAIL(bit_buffer->ReadBits(&bits_tmp, 2));
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// redundant_pic_cnt_present_flag: u(1)
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RETURN_EMPTY_ON_FAIL(
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bit_buffer->ReadBits(&pps.redundant_pic_cnt_present_flag, 1));
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return rtc::Optional<PpsParser::PpsState>(pps);
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}
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} // namespace webrtc
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