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/* Copyright (c) 2012 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,
M31 = 1.1
};
/**
* <code>PPB_Audio_Callback</code> defines the type of an audio callback
* function used to fill the audio buffer with data. Please see the
* Create() function in the <code>PPB_Audio</code> interface for
* more details on this callback.
*
* @param[in] sample_buffer A buffer to fill with audio data.
* @param[in] buffer_size_in_bytes The size of the buffer in bytes.
* @param[in] latency How long before the audio data is to be presented.
* @param[inout] user_data An opaque pointer that was passed into
* <code>PPB_Audio.Create()</code>.
*/
typedef void PPB_Audio_Callback([out] mem_t sample_buffer,
[in] uint32_t buffer_size_in_bytes,
[in, version=1.1] PP_TimeDelta latency,
[inout] mem_t user_data);
/**
* The <code>PPB_Audio</code> interface contains pointers to several functions
* for handling audio resources. Refer to the
* <a href="/native-client/devguide/coding/audio.html">Audio</a>
* chapter in the Developer's Guide 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
* <code>PPB_Audio</code> and <code>PPB_AudioConfig</code> follows.
*
* <strong>Example: </strong>
*
* @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 separate thread...
* @endcode
*/
interface PPB_Audio {
/**
* Create() 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 <code>PPB_Audio</code> 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 <code>AudioConfig</code> documentation.
*
* @param[in] instance A <code>PP_Instance</code> identifying one instance
* of a module.
* @param[in] config A <code>PP_Resource</code> corresponding to an audio
* config resource.
* @param[in] audio_callback A <code>PPB_Audio_Callback</code> 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 <code>PP_Resource</code> 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() determines if the provided resource is an audio resource.
*
* @param[in] resource A <code>PP_Resource</code> corresponding to a generic
* resource.
*
* @return A <code>PP_Bool</code> containing containing <code>PP_TRUE</code>
* if the given resource is an Audio resource, otherwise
* <code>PP_FALSE</code>.
*/
PP_Bool IsAudio(
[in] PP_Resource resource);
/**
* GetCurrrentConfig() returns an audio config resource for the given audio
* resource.
*
* @param[in] config A <code>PP_Resource</code> corresponding to an audio
* resource.
*
* @return A <code>PP_Resource</code> containing the audio config resource if
* successful.
*/
PP_Resource GetCurrentConfig(
[in] PP_Resource audio);
/**
* StartPlayback() starts the playback of the audio resource and begins
* periodically calling the callback.
*
* @param[in] config A <code>PP_Resource</code> corresponding to an audio
* resource.
*
* @return A <code>PP_Bool</code> containing <code>PP_TRUE</code> if
* successful, otherwise <code>PP_FALSE</code>. Also returns
* <code>PP_TRUE</code> (and be a no-op) if called while playback is already
* in progress.
*/
PP_Bool StartPlayback(
[in] PP_Resource audio);
/**
* StopPlayback() stops the playback of the audio resource.
*
* @param[in] config A <code>PP_Resource</code> corresponding to an audio
* resource.
*
* @return A <code>PP_Bool</code> containing <code>PP_TRUE</code> if
* successful, otherwise <code>PP_FALSE</code>. Also returns
* <code>PP_TRUE</code> (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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