XCVI. OpenAL Audio Bindings

简介

Platform independent audio bindings. Requires the OpenAL library.

安装

本 PECL 扩展未绑定于 PHP 中。

进一步信息例如新版本，下载，源程序，维护者信息以及更新日志可以在此找到： http://pecl.php.net/package/openal.

可以从 PHP 下载页面或者 http://snaps.php.net/ 下载此 PECL 扩展的 DLL 文件。

运行时配置

本扩展模块在 php.ini 中未定义任何配置选项。

资源类型

This extension defines four resource types: Open AL(Device) - Returned by openal_device_open(), Open AL(Context) - Returned by openal_context_create(), Open AL(Buffer) - Returned by openal_buffer_create(), and Open AL(Source) - Returned by openal_source_create().

预定义常量

以下常量由本扩展模块定义，因此只有在本扩展模块被编译到 PHP 中，或者在运行时被动态加载后才有效。

ALC_FREQUENCY (integer): Context Attribute
ALC_REFRESH (integer): Context Attribute
ALC_SYNC (integer): Context Attribute
AL_FREQUENCY (integer): Buffer Setting
AL_BITS (integer): Buffer Setting
AL_CHANNELS (integer): Buffer Setting
AL_SIZE (integer): Buffer Setting
AL_BUFFER (integer): Source/Listener Setting (Integer)
AL_SOURCE_RELATIVE (integer): Source/Listener Setting (Integer)
AL_SOURCE_STATE (integer): Source/Listener Setting (Integer)
AL_PITCH (integer): Source/Listener Setting (Float)
AL_GAIN (integer): Source/Listener Setting (Float)
AL_MIN_GAIN (integer): Source/Listener Setting (Float)
AL_MAX_GAIN (integer): Source/Listener Setting (Float)
AL_MAX_DISTANCE (integer): Source/Listener Setting (Float)
AL_ROLLOFF_FACTOR (integer): Source/Listener Setting (Float)
AL_CONE_OUTER_GAIN (integer): Source/Listener Setting (Float)
AL_CONE_INNER_ANGLE (integer): Source/Listener Setting (Float)
AL_CONE_OUTER_ANGLE (integer): Source/Listener Setting (Float)
AL_REFERENCE_DISTANCE (integer): Source/Listener Setting (Float)
AL_POSITION (integer): Source/Listener Setting (Float Vector)
AL_VELOCITY (integer): Source/Listener Setting (Float Vector)
AL_DIRECTION (integer): Source/Listener Setting (Float Vector)
AL_ORIENTATION (integer): Source/Listener Setting (Float Vector)
AL_FORMAT_MONO8 (integer): PCM Format
AL_FORMAT_MONO16 (integer): PCM Format
AL_FORMAT_STEREO8 (integer): PCM Format
AL_FORMAT_STEREO16 (integer): PCM Format
AL_INITIAL (integer): Source State
AL_PLAYING (integer): Source State
AL_PAUSED (integer): Source State
AL_STOPPED (integer): Source State
AL_LOOPING (integer): Source State
AL_TRUE (integer): Boolean value recognized by OpenAL
AL_FALSE (integer): Boolean value recognized by OpenAL

目录
openal_buffer_create -- Generate OpenAL buffer
openal_buffer_data -- Load a buffer with data
openal_buffer_destroy -- Destroys an OpenAL buffer
openal_buffer_get -- Retrieve an OpenAL buffer property
openal_buffer_loadwav -- Load a .wav file into a buffer
openal_context_create -- Create an audio processing context
openal_context_current -- Make the specified context current
openal_context_destroy -- Destroys a context
openal_context_process -- Process the specified context
openal_context_suspend -- Suspend the specified context
openal_device_close -- Close an OpenAL device
openal_device_open -- Initialize the OpenAL audio layer
openal_listener_get -- Retrieve a listener property
openal_listener_set -- Set a listener property
openal_source_create -- Generate a source resource
openal_source_destroy -- Destroy a source resource
openal_source_get -- Retrieve an OpenAL source property
openal_source_pause -- Pause the source
openal_source_play -- Start playing the source
openal_source_rewind -- Rewind the source
openal_source_set -- Set source property
openal_source_stop -- Stop playing the source
openal_stream -- Begin streaming on a source

add a note User Contributed Notes
OpenAL Audio Bindings

Tjeerd
02-Feb-2007 08:37


OpenAL aims to provide a standardized API for something called '3D' sound, just like OpenGL does for '3D' video rendering.



The fun part of OpenAL is that it does all the DSP for you, so you don't need to know a lot about audio. Since OpenAL comes from Creative Labs, it supports hardware rendering of audio with most if not all SoundBlaster audio controllers. They come with chips from EMU-systems and are specifically designed to mix down multichannel audio with DSP effects like reverb and chorus, which could consume a lot CPU speed.



The downside of OpenAL is that (at this time of writing) it is focus on games only. It doesn't do MIDI at all, it doesn't record anything, it doesn't work like a synthesizer. The only thing you can do with OpenAL is play sounds in a simulated 3D environment.

It probably doesn't work on the web.



To use OpenAL you need to read the documentation about OpenAL.



Note concerning audio users: there's no such thing as '3D' audio with speakers. Technically, when people have only two ears, they really can't distinguish sound from above or below, even in front or from behind. To achieve this people merely hear volume, the brightness of sound and the phase difference. One should be able to hear more '3D' sound with only two quality-class speakers than with a consumer class 5.1-set.

cweiske at cweiske dot de
06-Sep-2006 01:31


I made a PHP-Gtk2 OpenAL demo which allows you to define as many sound sources as you like and position them relative to the listener by drag and drop: http://gnope.org/p/Tools_OpenALdemo

cweiske at cweiske dot de
21-Jul-2006 11:29


Playing a wav file:

<?php

function printok($b) {

    echo $b ? " ok\n" : " error\n";

}



echo "Opening device";

$device = openal_device_open();

printok($device);



echo "Creating context";

$context = openal_context_create($device);

printok($context);

echo "Making context the current";

printok(openal_context_current($context));



//where we are

//echo "Setting listener position";

//printok(openal_listener_set(AL_POSITION, array(0, 0, 0)));

//echo "Setting listener orientation";

//printok(openal_listener_set(AL_ORIENTATION, array(0=>0,1 => 1, 2=>0, 3=> 0, 4=>4, 5=>5)));



echo "Creating buffer";

$buffer = openal_buffer_create();

echo "Loading wav";

printok(openal_buffer_loadwav($buffer, '/data/shared/vmware/newmessage.wav'));

echo "buffer stats\n";

echo " Frequency: " . openal_buffer_get($buffer, AL_FREQUENCY) . "\n";

echo " Bits     : " . openal_buffer_get($buffer, AL_BITS) . "\n";

echo " Channels : " . openal_buffer_get($buffer, AL_CHANNELS) . "\n";

echo " Size     : " . openal_buffer_get($buffer, AL_SIZE) . "\n";



echo "Creating source";

$source = openal_source_create();



echo "Setting source buffer";

printok(openal_source_set($source, AL_BUFFER, $buffer));

//echo "Setting source position";

//printok(openal_source_set($source, AL_POSITION, array(1, 0, 0)));



echo "Playing source";

printok(openal_source_play($source));



echo "sleeping\n";

//sleep(1);

//we wait 300msecs beause the sound

// has no time to be played otherwise

//since playing sound is done concurrently

// to the script

usleep(300000);



echo "Destroying source";

printok(openal_source_destroy($source));

echo "Destroying buffer";

printok(openal_buffer_destroy($buffer));

echo "Destroying context";

printok(openal_context_destroy($context));

echo "Closing device";

printok(openal_device_close($device));

?>

ganswijk at xs4all dot nl
31-Jan-2005 05:20


There is no explanation about what OpenAL actually is and you first have to follow quite a lot of links and download an SDK (from the Creative site) to get information about what OpenAL actually is, but here is what I understand it is:



It's a new standard to create a kind of 3D sound landscape in the way that OpenGL creates a visual 3D landscape. It's not a general sound card interface (as I was looking for). It doesn't handle MIDI and it can't handle sound input (yet).



I was hoping that I could experiment with a kind of homebrewed VoIP with this library but that's not the case.



BTW. The "links to the DLL", don't actually lead to an DLL and finding one is very hard and I haven't found one yet, but at least I know now that I don't have to search any further.



For the beautiful people making this excellent PHP site the great resource it is: Feel free to use this email as you seem fit...

add a note

openal_buffer_create

Usage

Last updated: Mon, 12 Sep 2005