add jitter buffer for voice

3 files changed, 100 insertions, 7 deletions

diff --git a/src/audio/jitterbuffer.hpp b/src/audio/jitterbuffer.hpp
new file mode 100644
index 0000000..3da3594
--- /dev/null
+++ b/src/audio/jitterbuffer.hpp
@@ -0,0 +1,82 @@
+#pragma once
+#include <chrono>
+#include <cstdint>
+#include <deque>
+
+// very simple non-RTP-based jitter buffer. does not handle out-of-order
+template<typename SampleFormat>
+class JitterBuffer {
+public:
+    /*
+     * desired_latency: how many milliseconds before audio can be drawn from buffer
+     * maximum_latency: how many milliseconds before old audio starts to be discarded
+     */
+    JitterBuffer(int desired_latency, int maximum_latency, int channels, int sample_rate)
+        : m_desired_latency(desired_latency)
+        , m_maximum_latency(maximum_latency)
+        , m_channels(channels)
+        , m_sample_rate(sample_rate)
+        , m_last_push(std::chrono::steady_clock::now()) {
+    }
+
+    [[nodiscard]] size_t Available() const noexcept {
+        return m_samples.size();
+    }
+
+    bool PopSamples(SampleFormat *ptr, size_t amount) {
+        CheckBuffering();
+        if (m_buffering || Available() < amount) return false;
+        std::copy(m_samples.begin(), m_samples.begin() + amount, ptr);
+        m_samples.erase(m_samples.begin(), m_samples.begin() + amount);
+        return true;
+    }
+
+    void PushSamples(SampleFormat *ptr, size_t amount) {
+        m_samples.insert(m_samples.end(), ptr, ptr + amount);
+        m_last_push = std::chrono::steady_clock::now();
+        const auto buffered = MillisBuffered();
+        if (buffered > m_maximum_latency) {
+            const auto overflow_ms = MillisBuffered() - m_maximum_latency;
+            const auto overflow_samples = overflow_ms * m_channels * m_sample_rate / 1000;
+            m_samples.erase(m_samples.begin(), m_samples.begin() + overflow_samples);
+        }
+    }
+
+private:
+    [[nodiscard]] size_t MillisBuffered() const {
+        return m_samples.size() * 1000 / m_channels / m_sample_rate;
+    }
+
+    void CheckBuffering() {
+        // if we arent buffering but the buffer is empty then we should be
+        if (m_samples.empty()) {
+            if (!m_buffering) {
+                m_buffering = true;
+            }
+            return;
+        }
+
+        if (!m_buffering) return;
+
+        // if we reached desired latency, we are sufficiently buffered
+        const auto millis_buffered = MillisBuffered();
+        if (millis_buffered >= m_desired_latency) {
+            m_buffering = false;
+        }
+        // if we havent buffered to desired latency but max latency has elapsed, exit buffering so it doesnt get stuck
+        const auto now = std::chrono::steady_clock::now();
+        const auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(now - m_last_push).count();
+        if (millis >= m_maximum_latency) {
+            m_buffering = false;
+        }
+    }
+
+    int m_desired_latency;
+    int m_maximum_latency;
+    int m_channels;
+    int m_sample_rate;
+    bool m_buffering = true;
+    std::chrono::time_point<std::chrono::steady_clock> m_last_push;
+
+    std::deque<SampleFormat> m_samples;
+};
diff --git a/src/audio/manager.cpp b/src/audio/manager.cpp
index eaac3bf..bb12f23 100644
--- a/src/audio/manager.cpp
+++ b/src/audio/manager.cpp
@@ -25,6 +25,7 @@ const uint8_t *StripRTPExtensionHeader(const uint8_t *buf, int num_bytes, size_t
     return buf;
 }
 
+// frameCount is configured to be 480 samples per channel
 void data_callback(ma_device *pDevice, void *pOutput, const void *pInput, ma_uint32 frameCount) {
     AudioManager *mgr = reinterpret_cast<AudioManager *>(pDevice->pUserData);
     if (mgr == nullptr) return;
@@ -36,12 +37,14 @@ void data_callback(ma_device *pDevice, void *pOutput, const void *pInput, ma_uin
         if (const auto vol_it = mgr->m_volume_ssrc.find(ssrc); vol_it != mgr->m_volume_ssrc.end()) {
             volume = vol_it->second;
         }
-        auto &buf = pair.first;
-        const size_t n = std::min(static_cast<size_t>(buf.size()), static_cast<size_t>(frameCount * 2ULL));
-        for (size_t i = 0; i < n; i++) {
+
+        static std::array<int16_t, 480 * 2> buf;
+
+        if (!pair.first.PopSamples(buf.data(), 480 * 2)) continue;
+
+        for (size_t i = 0; i < 480 * 2; i++) {
             pOutputF32[i] += volume * buf[i] / 32768.F;
         }
-        buf.erase(buf.begin(), buf.begin() + n);
     }
 }
 
@@ -201,7 +204,14 @@ void AudioManager::AddSSRC(uint32_t ssrc) {
     int error;
     if (m_sources.find(ssrc) == m_sources.end()) {
         auto *decoder = opus_decoder_create(48000, 2, &error);
-        m_sources.insert(std::make_pair(ssrc, std::make_pair(std::deque<int16_t> {}, decoder)));
+        auto &s = Abaddon::Get().GetSettings();
+        m_sources.insert(std::make_pair(ssrc, std::make_pair(
+                                                  JitterBuffer<int16_t>(
+                                                      s.JitterDesiredLatency,
+                                                      s.JitterMaximumLatency,
+                                                      2,
+                                                      48000),
+                                                  decoder)));
     }
 }
 
@@ -241,7 +251,7 @@ void AudioManager::FeedMeOpus(uint32_t ssrc, const std::vector<uint8_t> &data) {
         } else {
             UpdateReceiveVolume(ssrc, pcm.data(), decoded);
             auto &buf = it->second.first;
-            buf.insert(buf.end(), pcm.begin(), pcm.begin() + decoded * 2);
+            buf.PushSamples(pcm.data(), decoded * 2);
         }
     }
 }
diff --git a/src/audio/manager.hpp b/src/audio/manager.hpp
index 5716fc5..56882fd 100644
--- a/src/audio/manager.hpp
+++ b/src/audio/manager.hpp
@@ -21,6 +21,7 @@
 #endif
 
 #include "devices.hpp"
+#include "jitterbuffer.hpp"
 // clang-format on
 
 class AudioManager {
@@ -136,7 +137,7 @@ private:
     mutable std::mutex m_rnn_mutex;
 #endif
 
-    std::unordered_map<uint32_t, std::pair<std::deque<int16_t>, OpusDecoder *>> m_sources;
+    std::unordered_map<uint32_t, std::pair<JitterBuffer<int16_t>, OpusDecoder *>> m_sources;
 
     OpusEncoder *m_encoder;