mirror of https://github.com/NekoX-Dev/NekoX.git
253 lines
8.9 KiB
C++
253 lines
8.9 KiB
C++
/*
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* Copyright (c) 2021 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 "api/video_codecs/h264_profile_level_id.h"
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#include <cstdio>
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#include <cstdlib>
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#include <string>
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#include "rtc_base/arraysize.h"
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#include "rtc_base/checks.h"
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namespace webrtc {
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namespace {
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const char kProfileLevelId[] = "profile-level-id";
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// For level_idc=11 and profile_idc=0x42, 0x4D, or 0x58, the constraint set3
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// flag specifies if level 1b or level 1.1 is used.
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const uint8_t kConstraintSet3Flag = 0x10;
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// Convert a string of 8 characters into a byte where the positions containing
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// character c will have their bit set. For example, c = 'x', str = "x1xx0000"
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// will return 0b10110000. constexpr is used so that the pattern table in
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// kProfilePatterns is statically initialized.
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constexpr uint8_t ByteMaskString(char c, const char (&str)[9]) {
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return (str[0] == c) << 7 | (str[1] == c) << 6 | (str[2] == c) << 5 |
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(str[3] == c) << 4 | (str[4] == c) << 3 | (str[5] == c) << 2 |
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(str[6] == c) << 1 | (str[7] == c) << 0;
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}
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// Class for matching bit patterns such as "x1xx0000" where 'x' is allowed to be
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// either 0 or 1.
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class BitPattern {
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public:
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explicit constexpr BitPattern(const char (&str)[9])
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: mask_(~ByteMaskString('x', str)),
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masked_value_(ByteMaskString('1', str)) {}
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bool IsMatch(uint8_t value) const { return masked_value_ == (value & mask_); }
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private:
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const uint8_t mask_;
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const uint8_t masked_value_;
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};
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// Table for converting between profile_idc/profile_iop to H264Profile.
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struct ProfilePattern {
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const uint8_t profile_idc;
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const BitPattern profile_iop;
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const H264Profile profile;
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};
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// This is from https://tools.ietf.org/html/rfc6184#section-8.1.
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constexpr ProfilePattern kProfilePatterns[] = {
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{0x42, BitPattern("x1xx0000"), H264Profile::kProfileConstrainedBaseline},
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{0x4D, BitPattern("1xxx0000"), H264Profile::kProfileConstrainedBaseline},
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{0x58, BitPattern("11xx0000"), H264Profile::kProfileConstrainedBaseline},
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{0x42, BitPattern("x0xx0000"), H264Profile::kProfileBaseline},
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{0x58, BitPattern("10xx0000"), H264Profile::kProfileBaseline},
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{0x4D, BitPattern("0x0x0000"), H264Profile::kProfileMain},
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{0x64, BitPattern("00000000"), H264Profile::kProfileHigh},
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{0x64, BitPattern("00001100"), H264Profile::kProfileConstrainedHigh}};
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struct LevelConstraint {
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const int max_macroblocks_per_second;
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const int max_macroblock_frame_size;
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const H264Level level;
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};
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// This is from ITU-T H.264 (02/2016) Table A-1 – Level limits.
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static constexpr LevelConstraint kLevelConstraints[] = {
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{1485, 99, H264Level::kLevel1},
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{1485, 99, H264Level::kLevel1_b},
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{3000, 396, H264Level::kLevel1_1},
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{6000, 396, H264Level::kLevel1_2},
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{11880, 396, H264Level::kLevel1_3},
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{11880, 396, H264Level::kLevel2},
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{19800, 792, H264Level::kLevel2_1},
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{20250, 1620, H264Level::kLevel2_2},
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{40500, 1620, H264Level::kLevel3},
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{108000, 3600, H264Level::kLevel3_1},
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{216000, 5120, H264Level::kLevel3_2},
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{245760, 8192, H264Level::kLevel4},
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{245760, 8192, H264Level::kLevel4_1},
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{522240, 8704, H264Level::kLevel4_2},
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{589824, 22080, H264Level::kLevel5},
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{983040, 36864, H264Level::kLevel5_1},
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{2073600, 36864, H264Level::kLevel5_2},
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};
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} // anonymous namespace
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absl::optional<H264ProfileLevelId> ParseH264ProfileLevelId(const char* str) {
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// The string should consist of 3 bytes in hexadecimal format.
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if (strlen(str) != 6u)
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return absl::nullopt;
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const uint32_t profile_level_id_numeric = strtol(str, nullptr, 16);
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if (profile_level_id_numeric == 0)
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return absl::nullopt;
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// Separate into three bytes.
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const uint8_t level_idc =
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static_cast<uint8_t>(profile_level_id_numeric & 0xFF);
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const uint8_t profile_iop =
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static_cast<uint8_t>((profile_level_id_numeric >> 8) & 0xFF);
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const uint8_t profile_idc =
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static_cast<uint8_t>((profile_level_id_numeric >> 16) & 0xFF);
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// Parse level based on level_idc and constraint set 3 flag.
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H264Level level_casted = static_cast<H264Level>(level_idc);
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H264Level level;
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switch (level_casted) {
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case H264Level::kLevel1_1:
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level = (profile_iop & kConstraintSet3Flag) != 0 ? H264Level::kLevel1_b
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: H264Level::kLevel1_1;
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break;
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case H264Level::kLevel1:
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case H264Level::kLevel1_2:
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case H264Level::kLevel1_3:
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case H264Level::kLevel2:
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case H264Level::kLevel2_1:
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case H264Level::kLevel2_2:
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case H264Level::kLevel3:
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case H264Level::kLevel3_1:
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case H264Level::kLevel3_2:
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case H264Level::kLevel4:
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case H264Level::kLevel4_1:
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case H264Level::kLevel4_2:
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case H264Level::kLevel5:
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case H264Level::kLevel5_1:
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case H264Level::kLevel5_2:
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level = level_casted;
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break;
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default:
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// Unrecognized level_idc.
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return absl::nullopt;
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}
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// Parse profile_idc/profile_iop into a Profile enum.
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for (const ProfilePattern& pattern : kProfilePatterns) {
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if (profile_idc == pattern.profile_idc &&
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pattern.profile_iop.IsMatch(profile_iop)) {
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return H264ProfileLevelId(pattern.profile, level);
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}
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}
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// Unrecognized profile_idc/profile_iop combination.
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return absl::nullopt;
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}
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absl::optional<H264Level> H264SupportedLevel(int max_frame_pixel_count,
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float max_fps) {
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static const int kPixelsPerMacroblock = 16 * 16;
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for (int i = arraysize(kLevelConstraints) - 1; i >= 0; --i) {
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const LevelConstraint& level_constraint = kLevelConstraints[i];
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if (level_constraint.max_macroblock_frame_size * kPixelsPerMacroblock <=
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max_frame_pixel_count &&
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level_constraint.max_macroblocks_per_second <=
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max_fps * level_constraint.max_macroblock_frame_size) {
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return level_constraint.level;
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}
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}
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// No level supported.
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return absl::nullopt;
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}
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absl::optional<H264ProfileLevelId> ParseSdpForH264ProfileLevelId(
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const SdpVideoFormat::Parameters& params) {
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// TODO(magjed): The default should really be kProfileBaseline and kLevel1
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// according to the spec: https://tools.ietf.org/html/rfc6184#section-8.1. In
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// order to not break backwards compatibility with older versions of WebRTC
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// where external codecs don't have any parameters, use
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// kProfileConstrainedBaseline kLevel3_1 instead. This workaround will only be
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// done in an interim period to allow external clients to update their code.
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// http://crbug/webrtc/6337.
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static const H264ProfileLevelId kDefaultProfileLevelId(
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H264Profile::kProfileConstrainedBaseline, H264Level::kLevel3_1);
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const auto profile_level_id_it = params.find(kProfileLevelId);
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return (profile_level_id_it == params.end())
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? kDefaultProfileLevelId
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: ParseH264ProfileLevelId(profile_level_id_it->second.c_str());
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}
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absl::optional<std::string> H264ProfileLevelIdToString(
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const H264ProfileLevelId& profile_level_id) {
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// Handle special case level == 1b.
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if (profile_level_id.level == H264Level::kLevel1_b) {
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switch (profile_level_id.profile) {
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case H264Profile::kProfileConstrainedBaseline:
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return {"42f00b"};
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case H264Profile::kProfileBaseline:
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return {"42100b"};
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case H264Profile::kProfileMain:
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return {"4d100b"};
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// Level 1b is not allowed for other profiles.
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default:
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return absl::nullopt;
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}
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}
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const char* profile_idc_iop_string;
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switch (profile_level_id.profile) {
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case H264Profile::kProfileConstrainedBaseline:
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profile_idc_iop_string = "42e0";
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break;
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case H264Profile::kProfileBaseline:
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profile_idc_iop_string = "4200";
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break;
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case H264Profile::kProfileMain:
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profile_idc_iop_string = "4d00";
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break;
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case H264Profile::kProfileConstrainedHigh:
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profile_idc_iop_string = "640c";
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break;
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case H264Profile::kProfileHigh:
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profile_idc_iop_string = "6400";
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break;
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// Unrecognized profile.
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default:
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return absl::nullopt;
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}
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char str[7];
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snprintf(str, 7u, "%s%02x", profile_idc_iop_string, profile_level_id.level);
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return {str};
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}
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bool H264IsSameProfile(const SdpVideoFormat::Parameters& params1,
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const SdpVideoFormat::Parameters& params2) {
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const absl::optional<H264ProfileLevelId> profile_level_id =
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ParseSdpForH264ProfileLevelId(params1);
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const absl::optional<H264ProfileLevelId> other_profile_level_id =
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ParseSdpForH264ProfileLevelId(params2);
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// Compare H264 profiles, but not levels.
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return profile_level_id && other_profile_level_id &&
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profile_level_id->profile == other_profile_level_id->profile;
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}
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} // namespace webrtc
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