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/* Copyright (c) 2011 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.
*/
/**
* This file defines the <code>PPB_Audio</code> interface, which provides
* realtime stereo audio streaming capabilities.
*/
label Chrome {
M14 = 1.0
};
/**
* <code>PPB_Audio_Callback</code> defines the type of an audio callback
* function used to fill the audio buffer with data. Please see the
* <code>Create()</code> function in the <code>PPB_Audio</code> interface for
* more details on this callback.
*/
typedef void PPB_Audio_Callback([out] mem_t sample_buffer,
[in] uint32_t buffer_size_in_bytes,
[inout] mem_t user_data);
/**
* The <code>PPB_Audio</code> interface contains pointers to several functions
* for handling audio resources. Please refer to the
* <a href="/chrome/nativeclient/docs/audio.html">Pepper
* Audio API</a> for information on using this interface.
* Please see descriptions for each <code>PPB_Audio</code> and
* <code>PPB_AudioConfig</code> function for more details.
*
* A C example using PPB_Audio and PPB_AudioConfig:
* @code
* void audio_callback(void* sample_buffer,
* uint32_t buffer_size_in_bytes,
* void* user_data) {
* ... quickly fill in the buffer with samples and return to caller ...
* }
*
* ...Assume the application has cached the audio configuration interface in
* |audio_config_interface| and the audio interface in |audio_interface|...
*
* uint32_t count = audio_config_interface->RecommendSampleFrameCount(
* PP_AUDIOSAMPLERATE_44100, 4096);
* PP_Resource pp_audio_config = audio_config_interface->CreateStereo16Bit(
* pp_instance, PP_AUDIOSAMPLERATE_44100, count);
* PP_Resource pp_audio = audio_interface->Create(pp_instance, pp_audio_config,
* audio_callback, NULL);
* audio_interface->StartPlayback(pp_audio);
*
* ...audio_callback() will now be periodically invoked on a seperate thread...
* @endcode
*/
interface PPB_Audio {
/**
* Create is a pointer to a function that creates an audio resource.
* No sound will be heard until StartPlayback() is called. The callback
* is called with the buffer address and given user data whenever the
* buffer needs to be filled. From within the callback, you should not
* call PPB_Audio functions. The callback will be called on a different
* thread than the one which created the interface. For performance-critical
* applications (i.e. low-latency audio), the callback should avoid blocking
* or calling functions that can obtain locks, such as malloc. The layout and
* the size of the buffer passed to the audio callback will be determined by
* the device configuration and is specified in the AudioConfig documentation.
*
* @param[in] instance A PP_Instance indentifying one instance of a module.
* @param[in] config A PP_Resource containing the audio config resource.
* @param[in] audio_callback A PPB_Audio_Callback callback function that the
* browser calls when it needs more samples to play.
* @param[in] user_data A pointer to user data used in the callback function.
*
* @return A PP_Resource containing the audio resource if successful or
* 0 if the configuration cannot be honored or the callback is null.
*/
PP_Resource Create(
[in] PP_Instance instance,
[in] PP_Resource config,
[in] PPB_Audio_Callback audio_callback,
[inout] mem_t user_data);
/**
* IsAudio is a pointer to a function that determines if the given
* resource is an audio resource.
*
* @param[in] resource A PP_Resource containing a resource.
*
* @return A PP_BOOL containing containing PP_TRUE if the given resource is
* an Audio resource, otherwise PP_FALSE.
*/
PP_Bool IsAudio(
[in] PP_Resource resource);
/**
* GetCurrrentConfig is a pointer to a function that returns an audio config
* resource for the given audio resource.
*
* @param[in] config A PP_Resource containing the audio resource.
*
* @return A PP_Resource containing the audio config resource if successful.
*/
PP_Resource GetCurrentConfig(
[in] PP_Resource audio);
/**
* StartPlayback is a pointer to a function that starts the playback of
* the audio resource and begins periodically calling the callback.
*
* @param[in] config A PP_Resource containing the audio resource.
*
* @return A PP_BOOL containing PP_TRUE if successful, otherwise PP_FALSE.
* Also returns PP_TRUE (and be a no-op) if called while playback is already
* in progress.
*/
PP_Bool StartPlayback(
[in] PP_Resource audio);
/**
* StopPlayback is a pointer to a function that stops the playback of
* the audio resource.
*
* @param[in] config A PP_Resource containing the audio resource.
*
* @return A PP_BOOL containing PP_TRUE if successful, otherwise PP_FALSE.
* Also returns PP_TRUE (and is a no-op) if called while playback is already
* stopped. If a callback is in progress, StopPlayback will block until the
* callback completes.
*/
PP_Bool StopPlayback(
[in] PP_Resource audio);
};
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