LibWeb+LibMedia: Wire up setting the pipeline's playback rate

However, the playback rate is still limited to 1.0 at the element,
because audio stretching is not yet implemented.

Libraries/LibMedia/GenericTimeProvider.cpp

@@ -15,8 +15,12 @@ GenericTimeProvider::~GenericTimeProvider() = default;
 AK::Duration GenericTimeProvider::current_time() const
 {
     auto time = m_media_time;
-    if (m_monotonic_time_on_resume.has_value())
-        time += MonotonicTime::now() - m_monotonic_time_on_resume.value();
+    if (m_monotonic_time_on_resume.has_value()) {
+        auto elapsed = MonotonicTime::now() - m_monotonic_time_on_resume.value();
+        if (m_playback_rate != 1.0f)
+            elapsed = AK::Duration::from_seconds_f64(elapsed.to_seconds_f64() * m_playback_rate);
+        time += elapsed;
+    }
     return time;
 }
 
@@ -41,4 +45,16 @@ void GenericTimeProvider::seek(AK::Duration time)
     m_media_time = time;
 }
 
+void GenericTimeProvider::set_playback_rate(float rate)
+{
+    VERIFY(rate >= 0);
+    if (m_playback_rate == rate)
+        return;
+    if (m_monotonic_time_on_resume.has_value()) {
+        m_media_time = current_time();
+        m_monotonic_time_on_resume.emplace(MonotonicTime::now());
+    }
+    m_playback_rate = rate;
+}
+
 }

Libraries/LibMedia/GenericTimeProvider.h

@@ -19,10 +19,12 @@ public:
     virtual void resume() override;
     virtual void pause() override;
     virtual void seek(AK::Duration) override;
+    virtual void set_playback_rate(float) override;
 
 private:
     Optional<MonotonicTime> m_monotonic_time_on_resume;
     AK::Duration m_media_time;
+    float m_playback_rate { 1.0f };
 };
 
 }

Libraries/LibMedia/MediaTimeProvider.h

@@ -19,6 +19,7 @@ public:
     virtual void resume() = 0;
     virtual void pause() = 0;
     virtual void seek(AK::Duration) = 0;
+    virtual void set_playback_rate(float) = 0;
 };
 
 }

Libraries/LibMedia/PlaybackManager.cpp

@@ -301,6 +301,7 @@ void PlaybackManager::set_time_provider(NonnullRefPtr<MediaTimeProvider> const&
             continue;
         track_data.display->set_time_provider(provider);
     }
+    provider->set_playback_rate(m_playback_rate);
     if (is_playing())
         provider->resume();
 }
@@ -432,4 +433,10 @@ void PlaybackManager::set_volume(double volume)
         m_audio_sink->set_volume(volume);
 }
 
+void PlaybackManager::set_playback_rate(float rate)
+{
+    m_playback_rate = rate;
+    m_time_provider->set_playback_rate(rate);
+}
+
 }

Libraries/LibMedia/PlaybackManager.h

@@ -89,6 +89,7 @@ public:
     TimeRanges buffered_time_ranges() const;
 
     void set_volume(double);
+    void set_playback_rate(float);
 
     Function<void()> on_metadata_parsed;
     Function<void(DecoderError&&)> on_unsupported_format_error;
@@ -162,6 +163,7 @@ private:
     NonnullRefPtr<WeakPlaybackManagerLink> m_weak_link;
 
     NonnullRefPtr<MediaTimeProvider> m_time_provider;
+    float m_playback_rate { 1.0f };
 
     bool m_audio_output_disabled { false };
 

Libraries/LibMedia/Processors/AudioMixer.cpp

@@ -49,6 +49,7 @@ ErrorOr<void> AudioMixer::connect_input(NonnullRefPtr<AudioProducer> const& inpu
             disconnect_input_while_locked(input);
             return result.release_error();
         }
+        input->set_playback_rate(m_playback_rate);
         input->seek(mix_head_timestamp());
         if (m_started)
             input->start();
@@ -118,6 +119,16 @@ Audio::SampleSpecification AudioMixer::sample_specification() const
     return m_sample_specification;
 }
 
+void AudioMixer::set_playback_rate(float rate)
+{
+    Sync::MutexLocker locker { m_mutex };
+    if (m_playback_rate == rate)
+        return;
+    for (auto& [input, input_data] : m_inputs)
+        input->set_playback_rate(rate);
+    m_playback_rate = rate;
+}
+
 AK::Duration AudioMixer::mix_head_timestamp() const
 {
     return AK::Duration::from_time_units(m_next_frame_to_write, 1, m_sample_specification.sample_rate());

Libraries/LibMedia/Processors/AudioMixer.h

@@ -33,6 +33,8 @@ public:
 
     virtual void seek(AK::Duration timestamp) override;
 
+    virtual void set_playback_rate(float) override;
+
     virtual ErrorOr<void> set_output_sample_specification(Audio::SampleSpecification) override;
     Audio::SampleSpecification sample_specification() const;
 
@@ -60,6 +62,7 @@ private:
     Audio::SampleSpecification m_sample_specification;
     mutable HashMap<NonnullRefPtr<AudioProducer>, InputMixingData> m_inputs;
     i64 m_next_frame_to_write { 0 };
+    float m_playback_rate { 1.0f };
     bool m_started { false };
     bool m_moved_position_pending { false };
     mutable bool m_downstream_needs_wake { true };

Libraries/LibMedia/Producers/AudioProducer.h

@@ -26,6 +26,11 @@ public:
     virtual void set_wake_handler(PipelineWakeHandler) = 0;
 
     virtual void seek(AK::Duration timestamp) = 0;
+
+    virtual void set_playback_rate(float rate)
+    {
+        VERIFY(rate == 1.0f);
+    }
 };
 
 }

Libraries/LibMedia/Sinks/AudioPlaybackSink.cpp

@@ -49,6 +49,7 @@ public:
     size_t m_block_count { 0 };
     i64 m_next_frame_to_play { 0 };
     AudioBlockTimingRing m_block_timings;
+    float m_playback_rate { 1.0f };
 
     PipelineStateChangeHandler m_on_state_changed;
     PipelineStatus m_last_pull_status { PipelineStatus::Pending };
@@ -196,6 +197,7 @@ ErrorOr<void> AudioPlaybackSink::connect_input(NonnullRefPtr<AudioProducer> cons
             disconnect_input_while_locked(input);
             return result.release_error();
         }
+        input->set_playback_rate(m_output_thread_data->m_playback_rate);
         input->seek(current_time());
         input->start();
     }
@@ -467,4 +469,17 @@ void AudioPlaybackSink::set_volume(double volume)
     }
 }
 
+void AudioPlaybackSink::set_playback_rate(float rate)
+{
+    VERIFY(rate >= 0);
+    RefPtr<AudioProducer> input;
+    {
+        Sync::MutexLocker locker { m_output_thread_data->m_output_mutex };
+        input = m_output_thread_data->m_input;
+        m_output_thread_data->m_playback_rate = rate;
+    }
+    if (input != nullptr)
+        input->set_playback_rate(rate);
+}
+
 }

Libraries/LibMedia/Sinks/AudioPlaybackSink.h

@@ -40,6 +40,8 @@ public:
     virtual void pause() override;
     virtual void seek(AK::Duration) override;
 
+    virtual void set_playback_rate(float) override;
+
     void set_volume(double);
 
     Function<void(Error&&)> on_audio_output_error;

Libraries/LibWeb/HTML/HTMLMediaElement.cpp

@@ -1781,6 +1781,8 @@ void HTMLMediaElement::set_up_playback_manager_for_remote()
     m_playback_manager = Media::PlaybackManager::create();
     m_playback_manager->set_audio_output_disabled(document().page().client().is_headless());
 
+    m_playback_manager->set_playback_rate(static_cast<float>(m_playback_rate));
+
     m_has_enabled_preferred_audio_track = false;
     m_has_selected_preferred_video_track = false;
 
@@ -1856,6 +1858,8 @@ void HTMLMediaElement::set_up_playback_manager_for_local()
     m_playback_manager = Media::PlaybackManager::create();
     m_playback_manager->set_audio_output_disabled(document().page().client().is_headless());
 
+    m_playback_manager->set_playback_rate(static_cast<float>(m_playback_rate));
+
     m_has_enabled_preferred_audio_track = false;
     m_has_selected_preferred_video_track = false;
 
@@ -2602,9 +2606,11 @@ WebIDL::ExceptionOr<void> HTMLMediaElement::set_playback_rate(double new_value)
 
     // 2. Set playbackRate to the new value, and if the element is potentially playing, change the playback speed.
     m_playback_rate = new_value;
-    if (potentially_playing()) {
-        // FIXME: Do this once playback speeds other than 1 are supported.
-    }
+    // AD-HOC: Set the playback rate even when not potentially playing. The spec mandates that the media time advances
+    //         by playbackRate units of media time per unit time on the clock. There's no reason this shouldn't be set
+    //         always.
+    if (m_playback_manager)
+        m_playback_manager->set_playback_rate(static_cast<float>(new_value));
 
     return {};
 }