sdp_video_format_utils.cc

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/*

 *  Copyright (c) 2019 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 "media/base/sdp_video_format_utils.h"

#include <cstring>

#include <map>

#include <string>

#include <utility>

#include "api/video_codecs/h264_profile_level_id.h"

#ifdef RTC_ENABLE_H265

#include "api/video_codecs/h265_profile_tier_level.h"

#endif

#include "absl/algorithm/container.h"

#include "media/base/media_constants.h"

#include "rtc_base/checks.h"

#include "rtc_base/string_to_number.h"

namespace webrtc {

namespace {

const char kProfileLevelId[] = "profile-level-id";

const char kH264LevelAsymmetryAllowed[] = "level-asymmetry-allowed";

// Max frame rate for VP8 and VP9 video.

const char kVPxFmtpMaxFrameRate[] = "max-fr";

// Max frame size for VP8 and VP9 video.

const char kVPxFmtpMaxFrameSize[] = "max-fs";

const int kVPxFmtpFrameSizeSubBlockPixels = 256;

#ifdef RTC_ENABLE_H265

constexpr char kH265ProfileId[] = "profile-id";

constexpr char kH265TierFlag[] = "tier-flag";

constexpr char kH265LevelId[] = "level-id";

#endif

bool IsH264LevelAsymmetryAllowed(const CodecParameterMap& params) {

  const auto it = params.find(kH264LevelAsymmetryAllowed);

  return it != params.end() && strcmp(it->second.c_str(), "1") == 0;

// Compare H264 levels and handle the level 1b case.

bool H264LevelIsLess(H264Level a, H264Level b) {

  if (a == H264Level::kLevel1_b)

    return b != H264Level::kLevel1 && b != H264Level::kLevel1_b;

  if (b == H264Level::kLevel1_b)

    return a == H264Level::kLevel1;

  return a < b;

H264Level H264LevelMin(H264Level a, H264Level b) {

  return H264LevelIsLess(a, b) ? a : b;

absl::optional<int> ParsePositiveNumberFromParams(

    const CodecParameterMap& params,

    const char* parameter_name) {

  const auto max_frame_rate_it = params.find(parameter_name);

  if (max_frame_rate_it == params.end())

    return absl::nullopt;

  const absl::optional<int> i =

      rtc::StringToNumber<int>(max_frame_rate_it->second);

  if (!i.has_value() || i.value() <= 0)

    return absl::nullopt;

  return i;

#ifdef RTC_ENABLE_H265

// Compares two H265Level and return the smaller.

H265Level H265LevelMin(H265Level a, H265Level b) {

  return a <= b ? a : b;

// Returns true if none of profile-id/tier-flag/level-id is specified

// explicitly in the param.

bool IsDefaultH265PTL(const CodecParameterMap& params) {

  return !params.count(kH265ProfileId) && !params.count(kH265TierFlag) &&

         !params.count(kH265LevelId);

#endif

}  // namespace

#ifdef RTC_ENABLE_H265

// Set level according to https://tools.ietf.org/html/rfc7798#section-7.1

void H265GenerateProfileTierLevelForAnswer(

    const CodecParameterMap& local_supported_params,

    const CodecParameterMap& remote_offered_params,

    CodecParameterMap* answer_params) {

  // If local and remote haven't set profile-id/tier-flag/level-id, they

  // are both using the default PTL In this case, don't set PTL in answer

  // either.

  if (IsDefaultH265PTL(local_supported_params) &&

      IsDefaultH265PTL(remote_offered_params)) {

    return;

  // Parse profile-tier-level.

  const absl::optional<H265ProfileTierLevel> local_profile_tier_level =

      ParseSdpForH265ProfileTierLevel(local_supported_params);

  const absl::optional<H265ProfileTierLevel> remote_profile_tier_level =

      ParseSdpForH265ProfileTierLevel(remote_offered_params);

  // Profile and tier for local and remote codec must be valid and equal.

  RTC_DCHECK(local_profile_tier_level);

  RTC_DCHECK(remote_profile_tier_level);

  RTC_DCHECK_EQ(local_profile_tier_level->profile,

                remote_profile_tier_level->profile);

  RTC_DCHECK_EQ(local_profile_tier_level->tier,

                remote_profile_tier_level->tier);

  const H265Level answer_level = H265LevelMin(local_profile_tier_level->level,

                                              remote_profile_tier_level->level);

  // Level-id in answer is changable as long as the highest level indicated by

  // the answer is not higher than that indicated by the offer. See

  // https://tools.ietf.org/html/rfc7798#section-7.2.2, sub-clause 2.

  (*answer_params)[kH265LevelId] = H265LevelToString(answer_level);

#endif

// Set level according to https://tools.ietf.org/html/rfc6184#section-8.2.2.

void H264GenerateProfileLevelIdForAnswer(

    const CodecParameterMap& local_supported_params,

    const CodecParameterMap& remote_offered_params,

    CodecParameterMap* answer_params) {

  // If both local and remote haven't set profile-level-id, they are both using

  // the default profile. In this case, don't set profile-level-id in answer

  // either.

  if (!local_supported_params.count(kProfileLevelId) &&

      !remote_offered_params.count(kProfileLevelId)) {

    return;

  // Parse profile-level-ids.

  const absl::optional<H264ProfileLevelId> local_profile_level_id =

      ParseSdpForH264ProfileLevelId(local_supported_params);

  const absl::optional<H264ProfileLevelId> remote_profile_level_id =

      ParseSdpForH264ProfileLevelId(remote_offered_params);

  // The local and remote codec must have valid and equal H264 Profiles.

  RTC_DCHECK(local_profile_level_id);

  RTC_DCHECK(remote_profile_level_id);

  RTC_DCHECK_EQ(local_profile_level_id->profile,

                remote_profile_level_id->profile);

  // Parse level information.

  const bool level_asymmetry_allowed =

      IsH264LevelAsymmetryAllowed(local_supported_params) &&

      IsH264LevelAsymmetryAllowed(remote_offered_params);

  const H264Level local_level = local_profile_level_id->level;

  const H264Level remote_level = remote_profile_level_id->level;

  const H264Level min_level = H264LevelMin(local_level, remote_level);

  // Determine answer level. When level asymmetry is not allowed, level upgrade

  // is not allowed, i.e., the level in the answer must be equal to or lower

  // than the level in the offer.

  const H264Level answer_level =

      level_asymmetry_allowed ? local_level : min_level;

  // Set the resulting profile-level-id in the answer parameters.

  (*answer_params)[kProfileLevelId] = *H264ProfileLevelIdToString(

      H264ProfileLevelId(local_profile_level_id->profile, answer_level));

absl::optional<int> ParseSdpForVPxMaxFrameRate(

    const CodecParameterMap& params) {

  return ParsePositiveNumberFromParams(params, kVPxFmtpMaxFrameRate);

absl::optional<int> ParseSdpForVPxMaxFrameSize(

    const CodecParameterMap& params) {

  const absl::optional<int> i =

      ParsePositiveNumberFromParams(params, kVPxFmtpMaxFrameSize);

  return i ? absl::make_optional(i.value() * kVPxFmtpFrameSizeSubBlockPixels)

           : absl::nullopt;

bool SupportsPerLayerPictureLossIndication(const CodecParameterMap& params) {

  return absl::c_find_if(

             params, [](const std::pair<std::string, std::string>& kv) {

               return kv.first ==

                          cricket::kCodecParamPerLayerPictureLossIndication &&

                      kv.second == "1";

             }) != params.end();

}  // namespace webrtc