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1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef CHROMECAST_PUBLIC_CAST_AUDIO_OUTPUT_STREAM_H_ | |
6 #define CHROMECAST_PUBLIC_CAST_AUDIO_OUTPUT_STREAM_H_ | |
7 | |
8 #include <stdint.h> | |
9 | |
10 namespace chromecast { | |
11 namespace media { | |
12 | |
13 // A simple struct describing an audio stream. | |
14 struct AudioParameters { | |
15 int sample_rate; // Sampling frequency/rate. | |
16 int bits_per_sample; // Number of bits per sample. | |
17 int frames_per_buffer; // Number of frames in a buffer. | |
18 int channels; // Number of channels. | |
19 | |
20 static const int kMaxSampleRate = 192000; | |
21 static const int kMaxBitsPerSample = 32; | |
22 static const int kMaxFramesPerBuffer = kMaxSampleRate; | |
23 static const int kMaxChannels = 32; // The maximum number of channels. | |
24 }; | |
25 | |
26 // This is an interface for a Cast audio output stream. Implementations of this | |
27 // interface are responsible for making calls to an AudioSourceCallback. | |
28 class CastAudioOutputStream { | |
29 public: | |
30 // Audio sources must implement AudioSourceCallback. Calls to this interface | |
31 // must be made on the same thread on which the stream object is created. | |
32 class AudioSourceCallback { | |
33 protected: | |
34 virtual ~AudioSourceCallback() {} | |
byungchul
2015/07/30 22:12:16
protected should go after public ones.
| |
35 | |
36 public: | |
37 // The CastAudioOutputStream calls this to request more data from the | |
38 // source. This method fills |dest| with |frames| frames of interleaved | |
39 // data, which takes the following struture for N channels: | |
40 // | |
41 // [ch0, ch1, ..., chN, ch0, ch1, ..., chN, ...] | |
42 // |<---- Frame 0 ---->|<---- Frame 1 ---->|...| | |
43 // | |
44 // |len| is the size of |dest| in bytes, and must satisfy the following: | |
45 // | |
46 // |len| >= |frames| * (num channels) * (bytes per sample) | |
47 // | |
48 // where bytes per sample and channels are properties of the stream. These | |
49 // can be detemined through GetParameters(). |total_bytes_delay| contains | |
50 // the current number of bytes of delay buffered by the | |
51 // CastAudioOutputStream. Returns the number of frames successfully filled. | |
52 virtual int GetMoreData(void* dest, | |
53 uint32_t len, | |
54 int32_t frames, | |
55 uint32_t total_bytes_delay) = 0; | |
56 | |
57 // There was an error while playing a buffer. Audio source cannot be | |
58 // destroyed yet. No direct action needed by the AudioStream, but it is | |
59 // a good place to stop accumulating sound data since is is likely that | |
60 // playback will not continue. | |
61 virtual void OnError(CastAudioOutputStream* stream) = 0; | |
62 }; | |
63 | |
64 virtual ~CastAudioOutputStream() {} | |
65 | |
66 // Returns the parameters describing the stream. | |
67 virtual AudioParameters GetParameters() = 0; | |
68 | |
69 // Open the stream. A call to this method will always be followed by a call to | |
70 // Close() even if Open() fails. This method may block the caller's thread. | |
71 virtual bool Open() = 0; | |
72 | |
73 // Starts playing audio and generating AudioSourceCallback::GetMoreData(). | |
74 // Since implementor of CastAudioOutputStream may have internal buffers, right | |
75 // after calling this method initial buffers are fetched. | |
76 // | |
77 // The output stream does not take ownership of this callback. | |
78 virtual void Start(AudioSourceCallback* callback) = 0; | |
79 | |
80 // Stops playing audio. Effect might not be instantaneous as the hardware | |
81 // might have locked audio data that is processing. | |
82 virtual void Stop() = 0; | |
83 | |
84 // Sets the relative volume, with range [0.0, 1.0] inclusive. | |
85 virtual void SetVolume(double volume) = 0; | |
86 | |
87 // Gets the relative volume, with range [0.0, 1.0] inclusive. This method may | |
88 // be . | |
89 virtual double GetVolume() = 0; | |
90 | |
91 // Close the stream. This also generates AudioSourceCallback::OnClose(). | |
92 // After calling this method, the object should not be used anymore. Like all | |
93 // other methods, this must be made on the same thread on which the stream was | |
94 // created. | |
95 virtual void Close() = 0; | |
96 }; | |
97 | |
98 } // namespace media | |
99 } // namespace chromecast | |
100 | |
101 #endif // CHROMECAST_PUBLIC_CAST_AUDIO_OUTPUT_STREAM_H_ | |
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