Ogg Opus bitstream information. More...

#include <opusfile.h>

Data Fields
int	version
	The Ogg Opus format version, in the range 0...255.
int	channel_count
	The number of channels, in the range 1...255.
unsigned	pre_skip
	The number of samples that should be discarded from the beginning of the stream.
opus_uint32	input_sample_rate
	The sampling rate of the original input.
int	output_gain
	The gain to apply to the decoded output, in dB, as a Q8 value in the range.
int	mapping_family
	The channel mapping family, in the range 0...255.
int	stream_count
	The number of Opus streams in each Ogg packet, in the range 1...255.
int	coupled_count
	The number of coupled Opus streams in each Ogg packet, in the range 0...127.
unsigned char	mapping [OPUS_CHANNEL_COUNT_MAX]
	The mapping from coded stream channels to output channels.

Detailed Description

Ogg Opus bitstream information.

This contains the basic playback parameters for a stream, and corresponds to the initial ID header packet of an Ogg Opus stream.

Field Documentation

int OpusHead::version

The Ogg Opus format version, in the range 0...255.

The top 4 bits represent a "major" version, and the bottom four bits represent backwards-compatible "minor" revisions. The current specification describes version 1. This library will recognize versions up through 15 as backwards compatible with the current specification. An earlier draft of the specification described a version 0, but the only difference between version 1 and version 0 is that version 0 did not specify the semantics for handling the version field.

int OpusHead::channel_count

The number of channels, in the range 1...255.

unsigned OpusHead::pre_skip

The number of samples that should be discarded from the beginning of the stream.

opus_uint32 OpusHead::input_sample_rate

The sampling rate of the original input.

All Opus audio is coded at 48 kHz, and should also be decoded at 48 kHz for playback (unless the target hardware does not support this sampling rate). However, this field may be used to resample the audio back to the original sampling rate, for example, when saving the output to a file.

int OpusHead::output_gain

The gain to apply to the decoded output, in dB, as a Q8 value in the range.

-32768...32767. The decoder will automatically scale the output by pow(10,output_gain/(20.0*256)).

int OpusHead::mapping_family

The channel mapping family, in the range 0...255.

Channel mapping family 0 covers mono or stereo in a single stream. Channel mapping family 1 covers 1 to 8 channels in one or more streams, using the Vorbis speaker assignments. Channel mapping family 255 covers 1 to 255 channels in one or more streams, but without any defined speaker assignment.

int OpusHead::stream_count

The number of Opus streams in each Ogg packet, in the range 1...255.

int OpusHead::coupled_count

The number of coupled Opus streams in each Ogg packet, in the range 0...127.

This must satisfy 0 <= coupled_count <= stream_count and coupled_count + stream_count <= 255. The coupled streams appear first, before all uncoupled streams, in an Ogg Opus packet.

unsigned char OpusHead::mapping[OPUS_CHANNEL_COUNT_MAX]

The mapping from coded stream channels to output channels.

Let index=mapping[k] be the value for channel k. If index<2*coupled_count, then it refers to the left channel from stream (index/2) if even, and the right channel from stream (index/2) if odd. Otherwise, it refers to the output of the uncoupled stream (index-coupled_count).

The documentation for this struct was generated from the following file:

/home/derf/tmp/opusfile-0.2/include/opusfile.h

Data Fields

Detailed Description

Field Documentation