XIII. oggvorbis

About OGG/Vorbis

The OGG/Vorbis file format, as defined by http://www.vorbis.com/ and http://www.vorbis.com/, is a scheme for compressing audio streams by multiple factors with a minimum of quality loss. This extension adds oggvorbis support to PHP's URL Wrappers. When used in read mode, compressed OGG/Vorbis data is expanded to raw PCM audio in one of six PCM encoding formats listed below.

Prerequisite: PHP >= 4.3.0, libogg >= 1.0, and libvorbis >= 1.0.
pear install oggvorbis
Copy the resulting oggvorbis.so to an appropriate location and add extension=oggvorbis.so to your php.ini file or load it dynamically in your PHP script using dl("oggvorbis.so");

Table 1. OGG/Vorbis tuning options

Option	Definition	Relevance	Default
pcm_mode	PCM byte encoding used. See constants below.	Read / Write	`OGGVORBIS_PCM_S16_LE`
rate	PCM Sampling rate. Measured in Hz.	Write only	`44100`
bitrate	Vorbis Average Bitrate Encoding / Variable Bitrate Encoding. Measured in bps (ABR) or Quality level (VBR: 0.0 to 1.0). 128000 ABR is rough equal to 0.4 VBR.	Write only	`128000`
channels	Number of PCM channels. 1 == Mono, 2 == Stereo.	Write only	`2`
serialno	Serial Number of stream within file. Must be unique within file. Because of the potential to select a duplicate serial number within a chained file, make efforts to manually assign unique numbers when encoding.	Write only	Random
comments	Associative array of file comments. Will be translated to `strtoupper($name) . "=$value"`. Note: This context option is not available in oggvorbis-0.1	Write only	`array('ENCODER' => 'PHP/OggVorbis, http://pear.php.net/oggvorbis')`

Table 2. OGG/Vorbis supports PCM encodings in the following formats

Constant	Definition
`OGGVORBIS_PCM_U8`	Unsigned 8-bit PCM.
`OGGVORBIS_PCM_S8`	Signed 8-bit PCM.
`OGGVORBIS_PCM_U16_LE`	Unsigned 16-bit PCM. Little Endian byte order.
`OGGVORBIS_PCM_U16_BE`	Unsigned 16-bit PCM. Big Endian byte order.
`OGGVORBIS_PCM_S16_LE`	Signed 16-bit PCM. Little Endian byte order.
`OGGVORBIS_PCM_S16_BE`	Signed 16-bit PCM. Big Endian byte order.