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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <vector>
#include "media_pipeline_backend.h"
namespace chromecast {
namespace media {
// Direct audio source for the backend, used for low-latency audio output.
// All methods are called from a high-priority thread that is internal to the
// media backend, and therefore all methods should be threadsafe. Once a direct
// audio source has been added to the backend, it must not be deleted until
// after OnAudioPlaybackComplete() has been called on it.
class DirectAudioSource {
using RenderingDelay = MediaPipelineBackend::AudioDecoder::RenderingDelay;
// Returns the sample rate of audio provided by the source, in samples per
// second.
virtual int GetSampleRate() = 0;
// Returns the number of audio channels provided by the source. This is the
// number of channels that will be requested when FillAudioPlaybackFrames()
// is called.
virtual int GetNumChannels() = 0;
// Returns the desired playback buffer size in frames. This is the desired
// value for |num_frames| when FillAudioPlaybackFrames(); it affects the
// playback latency (larger value = higher latency). The backend may choose a
// different actual buffer size.
virtual int GetDesiredFillSize() = 0;
// Called when the source has been added to the backend, before any other
// calls are made. The |read_size| is the number of frames that will be
// requested for each call to FillAudioPlaybackFrames(). The
// |initial_rendering_delay| is the rendering delay estimate for the first
// call to FillAudioPlaybackFrames().
virtual void InitializeAudioPlayback(
int read_size,
RenderingDelay initial_rendering_delay) = 0;
// Called to read more audio data from the source. The source must fill in
// the |channels| with up to |num_frames| of audio. Note that only planar
// float format is supported.The |rendering_delay| indicates when the first
// frame of the filled data will be played out.
// Returns the number of frames filled.
virtual int FillAudioPlaybackFrames(int num_frames,
RenderingDelay rendering_delay,
const std::vector<float*>& channels) = 0;
// Called when an error occurs in audio playback. FillAudioPlaybackFrames()
// will not be called after an error occurs.
virtual void OnAudioPlaybackError() = 0;
// Called when audio playback is complete for this source. The source can only
// be safely deleted after OnAudioPlaybackComplete() has been called.
virtual void OnAudioPlaybackComplete() = 0;
virtual ~DirectAudioSource() = default;
} // namespace media
} // namespace chromecast