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/*
* 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 "common_video/h264/pps_parser.h"
#include <cstdint>
#include <vector>
#include "common_video/h264/h264_common.h"
#include "rtc_base/bit_buffer.h"
#include "rtc_base/checks.h"
#define RETURN_EMPTY_ON_FAIL(x) \
if (!(x)) { \
return absl::nullopt; \
}
namespace {
const int kMaxPicInitQpDeltaValue = 25;
const int kMinPicInitQpDeltaValue = -26;
} // namespace
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
absl::optional<PpsParser::PpsState> 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::vector<uint8_t> unpacked_buffer = H264::ParseRbsp(data, length);
rtc::BitBuffer bit_buffer(unpacked_buffer.data(), unpacked_buffer.size());
return ParseInternal(&bit_buffer);
}
bool PpsParser::ParsePpsIds(const uint8_t* data,
size_t length,
uint32_t* pps_id,
uint32_t* sps_id) {
RTC_DCHECK(pps_id);
RTC_DCHECK(sps_id);
// 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::vector<uint8_t> unpacked_buffer = H264::ParseRbsp(data, length);
rtc::BitBuffer bit_buffer(unpacked_buffer.data(), unpacked_buffer.size());
return ParsePpsIdsInternal(&bit_buffer, pps_id, sps_id);
}
absl::optional<uint32_t> PpsParser::ParsePpsIdFromSlice(const uint8_t* data,
size_t length) {
std::vector<uint8_t> unpacked_buffer = H264::ParseRbsp(data, length);
rtc::BitBuffer slice_reader(unpacked_buffer.data(), unpacked_buffer.size());
uint32_t golomb_tmp;
// first_mb_in_slice: ue(v)
if (!slice_reader.ReadExponentialGolomb(&golomb_tmp))
return absl::nullopt;
// slice_type: ue(v)
if (!slice_reader.ReadExponentialGolomb(&golomb_tmp))
return absl::nullopt;
// pic_parameter_set_id: ue(v)
uint32_t slice_pps_id;
if (!slice_reader.ReadExponentialGolomb(&slice_pps_id))
return absl::nullopt;
return slice_pps_id;
}
absl::optional<PpsParser::PpsState> PpsParser::ParseInternal(
rtc::BitBuffer* bit_buffer) {
PpsState pps;
RETURN_EMPTY_ON_FAIL(ParsePpsIdsInternal(bit_buffer, &pps.id, &pps.sps_id));
uint32_t bits_tmp;
uint32_t 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));
pps.entropy_coding_mode_flag = entropy_coding_mode_flag != 0;
// 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));
// Sanity-check parsed value
if (pps.pic_init_qp_minus26 > kMaxPicInitQpDeltaValue ||
pps.pic_init_qp_minus26 < kMinPicInitQpDeltaValue) {
RETURN_EMPTY_ON_FAIL(false);
}
// 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 pps;
}
bool PpsParser::ParsePpsIdsInternal(rtc::BitBuffer* bit_buffer,
uint32_t* pps_id,
uint32_t* sps_id) {
// pic_parameter_set_id: ue(v)
if (!bit_buffer->ReadExponentialGolomb(pps_id))
return false;
// seq_parameter_set_id: ue(v)
if (!bit_buffer->ReadExponentialGolomb(sps_id))
return false;
return true;
}
} // namespace webrtc
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