Note that although "ogg:" is the wrapper name, the stream is restricted to Ogg files containing a single stream encoded using the Vorbis audio codec. An Ogg container can, in fact, contain multiple streams: audio, video, anything. (Also, the audio streams in an Ogg contaner can use codecs such as FLAC and OggPCM.) The wrapper name is therefore misleading.
ogg:// — Audio streams
Files opened for reading via the ogg:// wrapper are treated as compressed audio encoded using the OGG/Vorbis codec. Similarly, files opened for writing or appending via the ogg:// wrapper are writen as compressed audio data. stream_get_meta_data(), when used on an OGG/Vorbis file opened for reading will return various details about the stream including the vendor tag, any included comments, the number of channels, the sampling rate, and the encoding rate range described by: bitrate_lower, bitrate_upper, bitrate_nominal, and bitrate_window.
ogg:// PHP 4.3.0 and up (PECL)