1 /*
2 * Copyright 2019 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "rtc_base/experiments/min_video_bitrate_experiment.h"
12
13 #include <string>
14
15 #include "rtc_base/checks.h"
16 #include "rtc_base/experiments/field_trial_parser.h"
17 #include "rtc_base/logging.h"
18 #include "system_wrappers/include/field_trial.h"
19
20 namespace webrtc {
21
22 const int kDefaultMinVideoBitrateBps = 30000;
23
24 namespace {
25 const char kForcedFallbackFieldTrial[] =
26 "WebRTC-VP8-Forced-Fallback-Encoder-v2";
27 const char kMinVideoBitrateExperiment[] = "WebRTC-Video-MinVideoBitrate";
28
GetFallbackMinBpsFromFieldTrial(VideoCodecType type)29 absl::optional<int> GetFallbackMinBpsFromFieldTrial(VideoCodecType type) {
30 if (type != kVideoCodecVP8) {
31 return absl::nullopt;
32 }
33
34 if (!webrtc::field_trial::IsEnabled(kForcedFallbackFieldTrial)) {
35 return absl::nullopt;
36 }
37
38 const std::string group =
39 webrtc::field_trial::FindFullName(kForcedFallbackFieldTrial);
40 if (group.empty()) {
41 return absl::nullopt;
42 }
43
44 int min_pixels; // Ignored.
45 int max_pixels; // Ignored.
46 int min_bps;
47 if (sscanf(group.c_str(), "Enabled-%d,%d,%d", &min_pixels, &max_pixels,
48 &min_bps) != 3) {
49 return absl::nullopt;
50 }
51
52 if (min_bps <= 0) {
53 return absl::nullopt;
54 }
55
56 return min_bps;
57 }
58 } // namespace
59
GetExperimentalMinVideoBitrate(VideoCodecType type)60 absl::optional<DataRate> GetExperimentalMinVideoBitrate(VideoCodecType type) {
61 const absl::optional<int> fallback_min_bitrate_bps =
62 GetFallbackMinBpsFromFieldTrial(type);
63 if (fallback_min_bitrate_bps) {
64 return DataRate::BitsPerSec(*fallback_min_bitrate_bps);
65 }
66
67 if (webrtc::field_trial::IsEnabled(kMinVideoBitrateExperiment)) {
68 webrtc::FieldTrialFlag enabled("Enabled");
69
70 // Backwards-compatibility with an old experiment - a generic minimum which,
71 // if set, applies to all codecs.
72 webrtc::FieldTrialOptional<webrtc::DataRate> min_video_bitrate("br");
73
74 // New experiment - per-codec minimum bitrate.
75 webrtc::FieldTrialOptional<webrtc::DataRate> min_bitrate_vp8("vp8_br");
76 webrtc::FieldTrialOptional<webrtc::DataRate> min_bitrate_vp9("vp9_br");
77 webrtc::FieldTrialOptional<webrtc::DataRate> min_bitrate_av1("av1_br");
78 webrtc::FieldTrialOptional<webrtc::DataRate> min_bitrate_h264("h264_br");
79
80 webrtc::ParseFieldTrial(
81 {&enabled, &min_video_bitrate, &min_bitrate_vp8, &min_bitrate_vp9,
82 &min_bitrate_av1, &min_bitrate_h264},
83 webrtc::field_trial::FindFullName(kMinVideoBitrateExperiment));
84
85 if (min_video_bitrate) {
86 if (min_bitrate_vp8 || min_bitrate_vp9 || min_bitrate_av1 ||
87 min_bitrate_h264) {
88 // "br" is mutually-exclusive with the other configuration possibilites.
89 RTC_LOG(LS_WARNING) << "Self-contradictory experiment config.";
90 }
91 return *min_video_bitrate;
92 }
93
94 switch (type) {
95 case kVideoCodecVP8:
96 return min_bitrate_vp8.GetOptional();
97 case kVideoCodecVP9:
98 return min_bitrate_vp9.GetOptional();
99 case kVideoCodecAV1:
100 return min_bitrate_av1.GetOptional();
101 case kVideoCodecH264:
102 return min_bitrate_h264.GetOptional();
103 case kVideoCodecGeneric:
104 case kVideoCodecMultiplex:
105 return absl::nullopt;
106 }
107
108 RTC_NOTREACHED();
109 }
110
111 return absl::nullopt;
112 }
113
114 } // namespace webrtc
115