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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.
#ifndef PPAPI_CPP_AUDIO_CONFIG_H_
#define PPAPI_CPP_AUDIO_CONFIG_H_
#include "ppapi/c/ppb_audio_config.h"
#include "ppapi/c/pp_stdint.h"
#include "ppapi/cpp/resource.h"
/// @file
/// This file defines the interface for establishing an
/// audio configuration resource within the browser.
namespace pp {
class Instance;
/// A 16 bit stereo AudioConfig resource. Refer to the
/// <a href="/chrome/nativeclient/docs/audio.html">Pepper
/// Audio API Code Walkthrough</a> for information on using this interface.
///
/// A single sample frame on a stereo device means one value for the left
/// channel and one value for the right channel.
///
/// Buffer layout for a stereo int16 configuration:
///
/// int16_t *buffer16;
/// buffer16[0] is the first left channel sample.
/// buffer16[1] is the first right channel sample.
/// buffer16[2] is the second left channel sample.
/// buffer16[3] is the second right channel sample.
/// ...
/// buffer16[2 * (sample_frame_count - 1)] is the last left channel sample.
/// buffer16[2 * (sample_frame_count - 1) + 1] is the last right channel
/// sample.
/// Data will always be in the native endian format of the platform.
///
/// <strong>Example:</strong>
/// @code
/// // Create an audio config with a supported frame count.
/// uint32_t sample_frame_count = AudioConfig::RecommendSampleFrameCount(
/// PP_AUDIOSAMPLERATE_44100, 4096);
/// AudioConfig config(PP_AUDIOSAMPLERATE_44100, sample_frame_count);
/// if (config.is_null())
/// return false; // Couldn't configure audio.
///
/// // Then use the config to create your audio resource.
/// Audio audio(instance, config, callback, user_data);
/// if (audio.is_null())
/// return false; // Couldn't create audio.
/// @endcode
class AudioConfig : public Resource {
public:
/// An empty constructor for an AudioConfig resource.
AudioConfig();
/// A constructor that creates an audio config based on the given sample rate
/// and frame count. If the rate and frame count aren't supported, the
/// resulting resource will be is_null(). You can pass the result of
/// RecommendSampleFrameCount() as the sample frame count.
///
/// @param[in] instance A pointer to an Instance indentifying one instance of
/// a module.
/// @param[in] sample_rate A PP_AudioSampleRate which is either
/// PP_AUDIOSAMPLERATE_44100 or PP_AUDIOSAMPLERATE_48000.
/// @param[in] sample_frame_count A uint32_t frame count returned from the
/// RecommendSampleFrameCount function.
AudioConfig(Instance* instance,
PP_AudioSampleRate sample_rate,
uint32_t sample_frame_count);
/// This function returns a supported frame count closest to the requested
/// count. The sample frame count determines the overall latency of audio.
/// Smaller frame counts will yield lower latency, but higher CPU
/// utilization. Supported sample frame counts will vary by hardware and
/// system (consider that the local system might be anywhere from a cell
/// phone or a high-end audio workstation). Sample counts less than
/// PP_AUDIOMINSAMPLEFRAMECOUNT and greater than PP_AUDIOMAXSAMPLEFRAMECOUNT
/// are never supported on any system, but values in between aren't
/// necessarily valid. This function will return a supported count closest to
/// the requested value for use in the constructor.
///
/// @param[in] sample_rate A PP_AudioSampleRate which is either
/// PP_AUDIOSAMPLERATE_44100 or PP_AUDIOSAMPLERATE_48000.
/// @param[in] requested_sample_frame_count A uint_32t requested frame count.
/// If you pass 0 as the requested sample count, the recommended sample for
/// the local system is returned.
/// @return A uint32_t containing the recommended sample frame count if
/// successful. If the sample frame count or bit rate is not supported,
/// this function will fail and 0.
static uint32_t RecommendSampleFrameCount(
PP_AudioSampleRate sample_rate,
uint32_t requested_sample_frame_count);
/// Getter function for returning the internal PP_AudioSampleRate enum.
/// @return The PP_AudioSampleRate enum.
PP_AudioSampleRate sample_rate() const { return sample_rate_; }
/// Getter function for returning the internal sample frame count.
/// @return A uint32_t containing the sample frame count.
uint32_t sample_frame_count() { return sample_frame_count_; }
private:
PP_AudioSampleRate sample_rate_;
uint32_t sample_frame_count_;
};
} // namespace pp
#endif // PPAPI_CPP_AUDIO_CONFIG_H_
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