| // Copyright 2016 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef SRC_MEDIA_AUDIO_AUDIO_CORE_THROTTLE_OUTPUT_H_ |
| #define SRC_MEDIA_AUDIO_AUDIO_CORE_THROTTLE_OUTPUT_H_ |
| |
| #include <fuchsia/media/cpp/fidl.h> |
| #include <lib/zx/time.h> |
| |
| #include <fbl/ref_ptr.h> |
| |
| #include "src/lib/fxl/synchronization/thread_annotations.h" |
| #include "src/lib/syslog/cpp/logger.h" |
| #include "src/media/audio/audio_core/audio_output.h" |
| |
| namespace media::audio { |
| |
| static constexpr zx::duration TRIM_PERIOD = zx::msec(10); |
| |
| // Throttle output may only be owned on the FIDL thread. |
| class ThrottleOutput : public AudioOutput { |
| public: |
| static std::shared_ptr<AudioOutput> Create(ThreadingModel* threading_model, |
| DeviceRegistry* registry, LinkMatrix* link_matrix) { |
| return std::make_shared<ThrottleOutput>(threading_model, registry, link_matrix); |
| } |
| |
| ThrottleOutput(ThreadingModel* threading_model, DeviceRegistry* registry, LinkMatrix* link_matrix) |
| : AudioOutput(threading_model, registry, link_matrix) { |
| // This is just some placeholder format that we can use to instantiate a mix |
| // stage for us. Since we never return a value from |StartMixJob|, we'll only |
| // ever trim on this mix stage, so the format here is not particularly |
| // important. |
| // |
| // Longer term we should just have something like a 'NullMixStage' that only |
| // has this trim capability. |
| |
| // This must be non-0, but it doesn't actually matter much since we'll never mix with a throttle |
| // output. |
| static const uint32_t kMaxBatchSize = PAGE_SIZE; |
| static PipelineConfig default_config = PipelineConfig::Default(); |
| SetupMixTask(default_config, 1, kMaxBatchSize, TimelineFunction()); |
| } |
| |
| ~ThrottleOutput() override = default; |
| |
| protected: |
| // AudioOutput Implementation |
| void OnWakeup() FXL_EXCLUSIVE_LOCKS_REQUIRED(mix_domain().token()) override { |
| if (uninitialized_) { |
| last_sched_time_ = async::Now(mix_domain().dispatcher()); |
| UpdatePlugState(true, zx::time(0)); |
| Process(); |
| uninitialized_ = false; |
| } |
| } |
| |
| std::optional<MixStage::FrameSpan> StartMixJob(zx::time process_start) override { |
| // Compute the next callback time; check whether trimming is falling behind. |
| last_sched_time_ = last_sched_time_ + TRIM_PERIOD; |
| if (process_start > last_sched_time_) { |
| // TODO(mpuryear): Trimming is falling behind. We should tell someone. |
| last_sched_time_ = process_start + TRIM_PERIOD; |
| } |
| |
| // TODO(mpuryear): Optimize the trim operation by scheduling callbacks for |
| // when our first pending packet ends, rather than polling . This will also |
| // tighten our timing in returning packets (currently, we hold packets up to |
| // [TRIM_PERIOD-episilon] past their end PTS before releasing). |
| // |
| // To do this, we would need wake and recompute, whenever an AudioRenderer |
| // client changes its rate transformation. For now, just polling is simpler. |
| SetNextSchedTime(last_sched_time_); |
| |
| // Throttle outputs don't actually mix; they provide backpressure to the |
| // pipeline by holding AudioPacket references until they are presented. We |
| // only need to schedule our next callback to keep things running, and let |
| // the base class implementation handle trimming the output. |
| return std::nullopt; |
| } |
| |
| void FinishMixJob(const MixStage::FrameSpan& span, float* buffer) override { |
| // Since we never start any jobs, this should never be called. |
| FX_DCHECK(false); |
| } |
| |
| // AudioDevice implementation. |
| // No one should ever be trying to apply gain limits for a throttle output. |
| void ApplyGainLimits(fuchsia::media::AudioGainInfo* in_out_info, uint32_t set_flags) override { |
| FX_DCHECK(false); |
| } |
| |
| private: |
| zx::time last_sched_time_; |
| bool uninitialized_ = true; |
| }; |
| |
| } // namespace media::audio |
| |
| #endif // SRC_MEDIA_AUDIO_AUDIO_CORE_THROTTLE_OUTPUT_H_ |