Injectable audio encoders: BuiltinAudioEncoderFactory

webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc

Index: webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
diff --git a/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc b/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
index 515f6c0f4215cf21cb8f1491c1014493df243003..2eedb5285e4f6139495d99d02e7caf2ba8808f8f 100644
--- a/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
+++ b/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.cc
@@ -10,6 +10,8 @@
 
 #include "webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.h"
 
+#include <stdlib.h>
+
 #include <algorithm>
 #include <iterator>
 
@@ -17,6 +19,7 @@
 #include "webrtc/base/logging.h"
 #include "webrtc/base/numerics/exp_filter.h"
 #include "webrtc/base/safe_conversions.h"
+#include "webrtc/base/string_to_number.h"
 #include "webrtc/base/timeutils.h"
 #include "webrtc/common_types.h"
 #include "webrtc/modules/audio_coding/audio_network_adaptor/audio_network_adaptor_impl.h"
@@ -28,6 +31,28 @@ namespace webrtc {
 
 namespace {
 
+// Codec parameters for Opus.
+// draft-spittka-payload-rtp-opus-03
+
+// Recommended bitrates:
+// 8-12 kb/s for NB speech,
+// 16-20 kb/s for WB speech,
+// 28-40 kb/s for FB speech,
+// 48-64 kb/s for FB mono music, and
+// 64-128 kb/s for FB stereo music.
+// The current implementation applies the following values to mono signals,
+// and multiplies them by 2 for stereo.
+const int kOpusBitrateNbBps = 12000;
+const int kOpusBitrateWbBps = 20000;
+const int kOpusBitrateFbBps = 32000;
+
+// Opus bitrate should be in the range between 6000 and 510000.
+const int kOpusMinBitrateBps = 6000;
+const int kOpusMaxBitrateBps = 510000;
+
+// TODO(ossu): These are from kCodecPrefs in webrtcvoiceengine.cc
+const int kOpusSupportedFrameLengths[] = {10, 20, 40, 60};
+
 constexpr int kSampleRateHz = 48000;
 
 // Opus API allows a min bitrate of 500bps, but Opus documentation suggests
@@ -37,9 +62,9 @@ constexpr int kMinBitrateBps = 6000;
 constexpr int kMaxBitrateBps = 512000;
 
 #if WEBRTC_OPUS_SUPPORT_120MS_PTIME
-constexpr int kSupportedFrameLengths[] = {20, 60, 120};
+constexpr int kANASupportedFrameLengths[] = {20, 60, 120};
 #else
-constexpr int kSupportedFrameLengths[] = {20, 60};
+constexpr int kANASupportedFrameLengths[] = {20, 60};
 #endif
 
 // PacketLossFractionSmoother uses an exponential filter with a time constant
@@ -103,6 +128,151 @@ float OptimizePacketLossRate(float new_loss_rate, float old_loss_rate) {
 
 }  // namespace
 
+rtc::Optional<AudioFormatInfo> AudioEncoderOpus::QueryAudioFormat(
+    const SdpAudioFormat& format) {
+  if (STR_CASE_CMP(format.name.c_str(), GetPayloadName()) == 0 &&
+      format.clockrate_hz == 48000 && format.num_channels == 2) {
+    int num_channels = 1;
+    const auto stereo_param = format.parameters.find("stereo");
+    if (stereo_param != format.parameters.end()) {
+      if (stereo_param->second == "1") {
+        num_channels = 2;
+      } else if (stereo_param->second != "0") {
+        return rtc::Optional<AudioFormatInfo>();
+      }
+    }
+
+    int max_playback_rate = 48000;
+    const auto maxplaybackrate_param =
+        format.parameters.find("maxplaybackrate");
+    if (maxplaybackrate_param != format.parameters.end()) {
+      const auto opt_max_playback_rate =
+          rtc::StringToNumber<int>(maxplaybackrate_param->second);
+      if (opt_max_playback_rate) {
+        max_playback_rate = *opt_max_playback_rate;
+        if (max_playback_rate <= 0) {
+          return rtc::Optional<AudioFormatInfo>();
+        }
+      }
+    }
+
+    int bitrate;
+    if (max_playback_rate && max_playback_rate <= 8000) {
+      bitrate = kOpusBitrateNbBps * num_channels;
+    } else if (max_playback_rate && max_playback_rate <= 16000) {
+      bitrate = kOpusBitrateWbBps * num_channels;
+    } else {
+      bitrate = kOpusBitrateFbBps * num_channels;
+    }
+
+    AudioFormatInfo info(48000, num_channels, bitrate, kOpusMinBitrateBps,
+                         kOpusMaxBitrateBps);
+    info.allow_comfort_noise = false;
+    info.supports_network_adaption = true;
+
+    return rtc::Optional<AudioFormatInfo>(info);
+  }
+  return rtc::Optional<AudioFormatInfo>();
+}
+
+AudioEncoderOpus::Config AudioEncoderOpus::CreateConfig(
+    int payload_type,
+    const SdpAudioFormat& format) {
+  auto get_param_int =
+      [&format] (const std::string& param) {
+        auto it = format.parameters.find(param);
+        if (it != format.parameters.end()) {
+          return rtc::StringToNumber<int>(it->second.c_str());
+        }
+        return rtc::Optional<int>();
+      };
+
+  auto get_param =
+      [&format] (const std::string& param) {
+        auto it = format.parameters.find(param);
+        return (it == format.parameters.end())
+            ? std::string()
+            : it->second;
+      };
+
+  AudioEncoderOpus::Config config;
+  config.num_channels = (get_param("stereo") == "1") ? 2 : 1;
+  config.fec_enabled = (get_param("useinbandfec") == "1");
+  config.dtx_enabled = (get_param("usedtx") == "1");
+  const auto max_playback_rate = get_param_int("maxplaybackrate");
+  if (max_playback_rate && *max_playback_rate > 0) {
+    config.max_playback_rate_hz = *max_playback_rate;
+  }
+  const auto max_average_bitrate = get_param_int("maxaveragebitrate");
+  bool use_param = true;
+  int bitrate = 0;
+  if (max_average_bitrate && *max_average_bitrate > 0) {
+    bitrate = *max_average_bitrate;
+  } else {
+    if (max_playback_rate && *max_playback_rate <= 8000) {
+      bitrate = kOpusBitrateNbBps * config.num_channels;
+    } else if (max_playback_rate && *max_playback_rate <= 16000) {
+      bitrate = kOpusBitrateWbBps * config.num_channels;
+    } else {
+      bitrate = kOpusBitrateFbBps * config.num_channels;
+    }
+    use_param = false;
+  }
+
+  if (bitrate < kOpusMinBitrateBps || bitrate > kOpusMaxBitrateBps) {
+    bitrate = (bitrate < kOpusMinBitrateBps) ? kOpusMinBitrateBps
+        : kOpusMaxBitrateBps;
+    std::string rate_source =
+        use_param ? "Codec parameter \"maxaveragebitrate\""
+        : "Default Opus bitrate";
+    LOG(LS_WARNING) << rate_source
+                    << " is invalid and is replaced by: " << bitrate;
+  }
+  config.bitrate_bps = rtc::Optional<int>(bitrate);
+  config.payload_type = payload_type;
+  config.application = config.num_channels == 1 ? AudioEncoderOpus::kVoip
+                                                : AudioEncoderOpus::kAudio;
+#if WEBRTC_OPUS_VARIABLE_COMPLEXITY
+  config.low_rate_complexity = 9;
+#endif
+
+  // TODO(ossu): What to do if ptime is not between minptime and maxptime?
+  const auto ptime = get_param_int("ptime");
+  if (ptime) {
+    // Expects kOpusSupportedFrameLengths to be sorted.
+    for (const int supported_frame_length : kOpusSupportedFrameLengths) {
+      if (supported_frame_length >= *ptime) {
+        config.frame_size_ms = *ptime;
+      }
+    }
+  }
+
+  const int min_frame_length_ms =
+      std::min(std::max(get_param_int("minptime").value_or(10), 10), 60);
+  const int max_frame_length_ms =
+      std::min(std::max(get_param_int("maxptime").value_or(60), 10), 60);
+  if (min_frame_length_ms <= max_frame_length_ms) {
+    for (const int frame_length_ms : kANASupportedFrameLengths) {
+      if (frame_length_ms >= min_frame_length_ms &&
+          frame_length_ms <= max_frame_length_ms) {
+        config.supported_frame_lengths_ms.push_back(frame_length_ms);
+      }
+    }
+  }
+
+  // As a fallback, just pick the whole set of supported frame lengths.
+  if (config.supported_frame_lengths_ms.empty()) {
+    for (const int frame_length_ms : kANASupportedFrameLengths) {
+      config.supported_frame_lengths_ms.push_back(frame_length_ms);
+    }
+  }
+
+  RTC_DCHECK(std::is_sorted(config.supported_frame_lengths_ms.begin(),
+                            config.supported_frame_lengths_ms.end()));
+
+  return config;
+}
+
 class AudioEncoderOpus::PacketLossFractionSmoother {
  public:
   explicit PacketLossFractionSmoother(const Clock* clock)
@@ -206,7 +376,11 @@ AudioEncoderOpus::AudioEncoderOpus(
 }
 
 AudioEncoderOpus::AudioEncoderOpus(const CodecInst& codec_inst)
-    : AudioEncoderOpus(CreateConfig(codec_inst), nullptr) {}
+    : AudioEncoderOpus(webrtc::CreateConfig(codec_inst), nullptr) {}
+
+AudioEncoderOpus::AudioEncoderOpus(int payload_type,
+                                   const SdpAudioFormat& format)
+    : AudioEncoderOpus(CreateConfig(payload_type, format), nullptr) {}
 
 AudioEncoderOpus::~AudioEncoderOpus() {
   RTC_CHECK_EQ(0, WebRtcOpus_EncoderFree(inst_));
@@ -367,8 +541,8 @@ void AudioEncoderOpus::SetReceiverFrameLengthRange(int min_frame_length_ms,
   RTC_DCHECK(!audio_network_adaptor_);
 
   config_.supported_frame_lengths_ms.clear();
-  std::copy_if(std::begin(kSupportedFrameLengths),
-               std::end(kSupportedFrameLengths),
+  std::copy_if(std::begin(kANASupportedFrameLengths),
+               std::end(kANASupportedFrameLengths),
                std::back_inserter(config_.supported_frame_lengths_ms),
                [&](int frame_length_ms) {
                  return frame_length_ms >= min_frame_length_ms &&