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Diffstat (limited to 'third_party/libwebrtc/api/video_codecs/h264_profile_level_id.cc')
-rw-r--r-- | third_party/libwebrtc/api/video_codecs/h264_profile_level_id.cc | 257 |
1 files changed, 257 insertions, 0 deletions
diff --git a/third_party/libwebrtc/api/video_codecs/h264_profile_level_id.cc b/third_party/libwebrtc/api/video_codecs/h264_profile_level_id.cc new file mode 100644 index 0000000000..5844ca0e32 --- /dev/null +++ b/third_party/libwebrtc/api/video_codecs/h264_profile_level_id.cc @@ -0,0 +1,257 @@ +/* + * Copyright (c) 2021 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 "api/video_codecs/h264_profile_level_id.h" + +#include <cstdio> +#include <cstdlib> +#include <string> + +#include "rtc_base/arraysize.h" +#include "rtc_base/checks.h" + +namespace webrtc { + +namespace { + +const char kProfileLevelId[] = "profile-level-id"; + +// For level_idc=11 and profile_idc=0x42, 0x4D, or 0x58, the constraint set3 +// flag specifies if level 1b or level 1.1 is used. +const uint8_t kConstraintSet3Flag = 0x10; + +// Convert a string of 8 characters into a byte where the positions containing +// character c will have their bit set. For example, c = 'x', str = "x1xx0000" +// will return 0b10110000. constexpr is used so that the pattern table in +// kProfilePatterns is statically initialized. +constexpr uint8_t ByteMaskString(char c, const char (&str)[9]) { + return (str[0] == c) << 7 | (str[1] == c) << 6 | (str[2] == c) << 5 | + (str[3] == c) << 4 | (str[4] == c) << 3 | (str[5] == c) << 2 | + (str[6] == c) << 1 | (str[7] == c) << 0; +} + +// Class for matching bit patterns such as "x1xx0000" where 'x' is allowed to be +// either 0 or 1. +class BitPattern { + public: + explicit constexpr BitPattern(const char (&str)[9]) + : mask_(~ByteMaskString('x', str)), + masked_value_(ByteMaskString('1', str)) {} + + bool IsMatch(uint8_t value) const { return masked_value_ == (value & mask_); } + + private: + const uint8_t mask_; + const uint8_t masked_value_; +}; + +// Table for converting between profile_idc/profile_iop to H264Profile. +struct ProfilePattern { + const uint8_t profile_idc; + const BitPattern profile_iop; + const H264Profile profile; +}; + +// This is from https://tools.ietf.org/html/rfc6184#section-8.1. +constexpr ProfilePattern kProfilePatterns[] = { + {0x42, BitPattern("x1xx0000"), H264Profile::kProfileConstrainedBaseline}, + {0x4D, BitPattern("1xxx0000"), H264Profile::kProfileConstrainedBaseline}, + {0x58, BitPattern("11xx0000"), H264Profile::kProfileConstrainedBaseline}, + {0x42, BitPattern("x0xx0000"), H264Profile::kProfileBaseline}, + {0x58, BitPattern("10xx0000"), H264Profile::kProfileBaseline}, + {0x4D, BitPattern("0x0x0000"), H264Profile::kProfileMain}, + {0x64, BitPattern("00000000"), H264Profile::kProfileHigh}, + {0x64, BitPattern("00001100"), H264Profile::kProfileConstrainedHigh}, + {0xF4, BitPattern("00000000"), H264Profile::kProfilePredictiveHigh444}}; + +struct LevelConstraint { + const int max_macroblocks_per_second; + const int max_macroblock_frame_size; + const H264Level level; +}; + +// This is from ITU-T H.264 (02/2016) Table A-1 – Level limits. +static constexpr LevelConstraint kLevelConstraints[] = { + {1485, 99, H264Level::kLevel1}, + {1485, 99, H264Level::kLevel1_b}, + {3000, 396, H264Level::kLevel1_1}, + {6000, 396, H264Level::kLevel1_2}, + {11880, 396, H264Level::kLevel1_3}, + {11880, 396, H264Level::kLevel2}, + {19800, 792, H264Level::kLevel2_1}, + {20250, 1620, H264Level::kLevel2_2}, + {40500, 1620, H264Level::kLevel3}, + {108000, 3600, H264Level::kLevel3_1}, + {216000, 5120, H264Level::kLevel3_2}, + {245760, 8192, H264Level::kLevel4}, + {245760, 8192, H264Level::kLevel4_1}, + {522240, 8704, H264Level::kLevel4_2}, + {589824, 22080, H264Level::kLevel5}, + {983040, 36864, H264Level::kLevel5_1}, + {2073600, 36864, H264Level::kLevel5_2}, +}; + +} // anonymous namespace + +absl::optional<H264ProfileLevelId> ParseH264ProfileLevelId(const char* str) { + // The string should consist of 3 bytes in hexadecimal format. + if (strlen(str) != 6u) + return absl::nullopt; + const uint32_t profile_level_id_numeric = strtol(str, nullptr, 16); + if (profile_level_id_numeric == 0) + return absl::nullopt; + + // Separate into three bytes. + const uint8_t level_idc = + static_cast<uint8_t>(profile_level_id_numeric & 0xFF); + const uint8_t profile_iop = + static_cast<uint8_t>((profile_level_id_numeric >> 8) & 0xFF); + const uint8_t profile_idc = + static_cast<uint8_t>((profile_level_id_numeric >> 16) & 0xFF); + + // Parse level based on level_idc and constraint set 3 flag. + H264Level level_casted = static_cast<H264Level>(level_idc); + H264Level level; + + switch (level_casted) { + case H264Level::kLevel1_1: + level = (profile_iop & kConstraintSet3Flag) != 0 ? H264Level::kLevel1_b + : H264Level::kLevel1_1; + break; + case H264Level::kLevel1: + case H264Level::kLevel1_2: + case H264Level::kLevel1_3: + case H264Level::kLevel2: + case H264Level::kLevel2_1: + case H264Level::kLevel2_2: + case H264Level::kLevel3: + case H264Level::kLevel3_1: + case H264Level::kLevel3_2: + case H264Level::kLevel4: + case H264Level::kLevel4_1: + case H264Level::kLevel4_2: + case H264Level::kLevel5: + case H264Level::kLevel5_1: + case H264Level::kLevel5_2: + level = level_casted; + break; + default: + // Unrecognized level_idc. + return absl::nullopt; + } + + // Parse profile_idc/profile_iop into a Profile enum. + for (const ProfilePattern& pattern : kProfilePatterns) { + if (profile_idc == pattern.profile_idc && + pattern.profile_iop.IsMatch(profile_iop)) { + return H264ProfileLevelId(pattern.profile, level); + } + } + + // Unrecognized profile_idc/profile_iop combination. + return absl::nullopt; +} + +absl::optional<H264Level> H264SupportedLevel(int max_frame_pixel_count, + float max_fps) { + static const int kPixelsPerMacroblock = 16 * 16; + + for (int i = arraysize(kLevelConstraints) - 1; i >= 0; --i) { + const LevelConstraint& level_constraint = kLevelConstraints[i]; + if (level_constraint.max_macroblock_frame_size * kPixelsPerMacroblock <= + max_frame_pixel_count && + level_constraint.max_macroblocks_per_second <= + max_fps * level_constraint.max_macroblock_frame_size) { + return level_constraint.level; + } + } + + // No level supported. + return absl::nullopt; +} + +absl::optional<H264ProfileLevelId> ParseSdpForH264ProfileLevelId( + const SdpVideoFormat::Parameters& params) { + // TODO(magjed): The default should really be kProfileBaseline and kLevel1 + // according to the spec: https://tools.ietf.org/html/rfc6184#section-8.1. In + // order to not break backwards compatibility with older versions of WebRTC + // where external codecs don't have any parameters, use + // kProfileConstrainedBaseline kLevel3_1 instead. This workaround will only be + // done in an interim period to allow external clients to update their code. + // http://crbug/webrtc/6337. + static const H264ProfileLevelId kDefaultProfileLevelId( + H264Profile::kProfileConstrainedBaseline, H264Level::kLevel3_1); + + const auto profile_level_id_it = params.find(kProfileLevelId); + return (profile_level_id_it == params.end()) + ? kDefaultProfileLevelId + : ParseH264ProfileLevelId(profile_level_id_it->second.c_str()); +} + +absl::optional<std::string> H264ProfileLevelIdToString( + const H264ProfileLevelId& profile_level_id) { + // Handle special case level == 1b. + if (profile_level_id.level == H264Level::kLevel1_b) { + switch (profile_level_id.profile) { + case H264Profile::kProfileConstrainedBaseline: + return {"42f00b"}; + case H264Profile::kProfileBaseline: + return {"42100b"}; + case H264Profile::kProfileMain: + return {"4d100b"}; + // Level 1b is not allowed for other profiles. + default: + return absl::nullopt; + } + } + + const char* profile_idc_iop_string; + switch (profile_level_id.profile) { + case H264Profile::kProfileConstrainedBaseline: + profile_idc_iop_string = "42e0"; + break; + case H264Profile::kProfileBaseline: + profile_idc_iop_string = "4200"; + break; + case H264Profile::kProfileMain: + profile_idc_iop_string = "4d00"; + break; + case H264Profile::kProfileConstrainedHigh: + profile_idc_iop_string = "640c"; + break; + case H264Profile::kProfileHigh: + profile_idc_iop_string = "6400"; + break; + case H264Profile::kProfilePredictiveHigh444: + profile_idc_iop_string = "f400"; + break; + // Unrecognized profile. + default: + return absl::nullopt; + } + + char str[7]; + snprintf(str, 7u, "%s%02x", profile_idc_iop_string, + static_cast<unsigned>(profile_level_id.level)); + return {str}; +} + +bool H264IsSameProfile(const SdpVideoFormat::Parameters& params1, + const SdpVideoFormat::Parameters& params2) { + const absl::optional<H264ProfileLevelId> profile_level_id = + ParseSdpForH264ProfileLevelId(params1); + const absl::optional<H264ProfileLevelId> other_profile_level_id = + ParseSdpForH264ProfileLevelId(params2); + // Compare H264 profiles, but not levels. + return profile_level_id && other_profile_level_id && + profile_level_id->profile == other_profile_level_id->profile; +} + +} // namespace webrtc |