Audio channels

Audio channel layout utility functions. More...

Modules
	Audio channel masks
	A channel layout is a 64-bits integer with a bit set for every channel.
	Audio channel layouts

Files
file	channel_layout.h
	Public libavutil channel layout APIs header.

Data Structures
struct	AVChannelCustom
	An AVChannelCustom defines a single channel within a custom order layout. More...
struct	AVChannelLayout
	An AVChannelLayout holds information about the channel layout of audio data. More...

Macros
#define	AV_CHANNEL_LAYOUT_MASK(nb, m)
	Macro to define native channel layouts.

Enumerations
enum	AVChannel {   AV_CHAN_NONE = -1 , AV_CHAN_FRONT_LEFT , AV_CHAN_FRONT_RIGHT , AV_CHAN_FRONT_CENTER ,   AV_CHAN_LOW_FREQUENCY , AV_CHAN_BACK_LEFT , AV_CHAN_BACK_RIGHT , AV_CHAN_FRONT_LEFT_OF_CENTER ,   AV_CHAN_FRONT_RIGHT_OF_CENTER , AV_CHAN_BACK_CENTER , AV_CHAN_SIDE_LEFT , AV_CHAN_SIDE_RIGHT ,   AV_CHAN_TOP_CENTER , AV_CHAN_TOP_FRONT_LEFT , AV_CHAN_TOP_FRONT_CENTER , AV_CHAN_TOP_FRONT_RIGHT ,   AV_CHAN_TOP_BACK_LEFT , AV_CHAN_TOP_BACK_CENTER , AV_CHAN_TOP_BACK_RIGHT , AV_CHAN_STEREO_LEFT = 29 ,   AV_CHAN_STEREO_RIGHT , AV_CHAN_WIDE_LEFT , AV_CHAN_WIDE_RIGHT , AV_CHAN_SURROUND_DIRECT_LEFT ,   AV_CHAN_SURROUND_DIRECT_RIGHT , AV_CHAN_LOW_FREQUENCY_2 , AV_CHAN_TOP_SIDE_LEFT , AV_CHAN_TOP_SIDE_RIGHT ,   AV_CHAN_BOTTOM_FRONT_CENTER , AV_CHAN_BOTTOM_FRONT_LEFT , AV_CHAN_BOTTOM_FRONT_RIGHT , AV_CHAN_UNUSED = 0x200 ,   AV_CHAN_UNKNOWN = 0x300 , AV_CHAN_AMBISONIC_BASE = 0x400 , AV_CHAN_AMBISONIC_END = 0x7ff }
enum	AVChannelOrder { AV_CHANNEL_ORDER_UNSPEC , AV_CHANNEL_ORDER_NATIVE , AV_CHANNEL_ORDER_CUSTOM , AV_CHANNEL_ORDER_AMBISONIC }

Functions
int	av_channel_name (char *buf, size_t buf_size, enum AVChannel channel)
	Get a human readable string in an abbreviated form describing a given channel.
void	av_channel_name_bprint (struct AVBPrint *bp, enum AVChannel channel_id)
	bprint variant of av_channel_name().
int	av_channel_description (char *buf, size_t buf_size, enum AVChannel channel)
	Get a human readable string describing a given channel.
void	av_channel_description_bprint (struct AVBPrint *bp, enum AVChannel channel_id)
	bprint variant of av_channel_description().
enum AVChannel	av_channel_from_string (const char *name)
	This is the inverse function of av_channel_name().
int	av_channel_layout_from_mask (AVChannelLayout *channel_layout, uint64_t mask)
	Initialize a native channel layout from a bitmask indicating which channels are present.
int	av_channel_layout_from_string (AVChannelLayout *channel_layout, const char *str)
	Initialize a channel layout from a given string description.
void	av_channel_layout_default (AVChannelLayout *ch_layout, int nb_channels)
	Get the default channel layout for a given number of channels.
const AVChannelLayout *	av_channel_layout_standard (void **opaque)
	Iterate over all standard channel layouts.
void	av_channel_layout_uninit (AVChannelLayout *channel_layout)
	Free any allocated data in the channel layout and reset the channel count to 0.
int	av_channel_layout_copy (AVChannelLayout *dst, const AVChannelLayout *src)
	Make a copy of a channel layout.
int	av_channel_layout_describe (const AVChannelLayout *channel_layout, char *buf, size_t buf_size)
	Get a human-readable string describing the channel layout properties.
int	av_channel_layout_describe_bprint (const AVChannelLayout *channel_layout, struct AVBPrint *bp)
	bprint variant of av_channel_layout_describe().
enum AVChannel	av_channel_layout_channel_from_index (const AVChannelLayout *channel_layout, unsigned int idx)
	Get the channel with the given index in a channel layout.
int	av_channel_layout_index_from_channel (const AVChannelLayout *channel_layout, enum AVChannel channel)
	Get the index of a given channel in a channel layout.
int	av_channel_layout_index_from_string (const AVChannelLayout *channel_layout, const char *name)
	Get the index in a channel layout of a channel described by the given string.
enum AVChannel	av_channel_layout_channel_from_string (const AVChannelLayout *channel_layout, const char *name)
	Get a channel described by the given string.
uint64_t	av_channel_layout_subset (const AVChannelLayout *channel_layout, uint64_t mask)
	Find out what channels from a given set are present in a channel layout, without regard for their positions.
int	av_channel_layout_check (const AVChannelLayout *channel_layout)
	Check whether a channel layout is valid, i.e.
int	av_channel_layout_compare (const AVChannelLayout *chl, const AVChannelLayout *chl1)
	Check whether two channel layouts are semantically the same, i.e.

Common pre-defined channel layouts
#define	AV_CHANNEL_LAYOUT_MONO   AV_CHANNEL_LAYOUT_MASK(1, AV_CH_LAYOUT_MONO)
#define	AV_CHANNEL_LAYOUT_STEREO   AV_CHANNEL_LAYOUT_MASK(2, AV_CH_LAYOUT_STEREO)
#define	AV_CHANNEL_LAYOUT_2POINT1   AV_CHANNEL_LAYOUT_MASK(3, AV_CH_LAYOUT_2POINT1)
#define	AV_CHANNEL_LAYOUT_2_1   AV_CHANNEL_LAYOUT_MASK(3, AV_CH_LAYOUT_2_1)
#define	AV_CHANNEL_LAYOUT_SURROUND   AV_CHANNEL_LAYOUT_MASK(3, AV_CH_LAYOUT_SURROUND)
#define	AV_CHANNEL_LAYOUT_3POINT1   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_3POINT1)
#define	AV_CHANNEL_LAYOUT_4POINT0   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_4POINT0)
#define	AV_CHANNEL_LAYOUT_4POINT1   AV_CHANNEL_LAYOUT_MASK(5, AV_CH_LAYOUT_4POINT1)
#define	AV_CHANNEL_LAYOUT_2_2   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_2_2)
#define	AV_CHANNEL_LAYOUT_QUAD   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_QUAD)
#define	AV_CHANNEL_LAYOUT_5POINT0   AV_CHANNEL_LAYOUT_MASK(5, AV_CH_LAYOUT_5POINT0)
#define	AV_CHANNEL_LAYOUT_5POINT1   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_5POINT1)
#define	AV_CHANNEL_LAYOUT_5POINT0_BACK   AV_CHANNEL_LAYOUT_MASK(5, AV_CH_LAYOUT_5POINT0_BACK)
#define	AV_CHANNEL_LAYOUT_5POINT1_BACK   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_5POINT1_BACK)
#define	AV_CHANNEL_LAYOUT_6POINT0   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_6POINT0)
#define	AV_CHANNEL_LAYOUT_6POINT0_FRONT   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_6POINT0_FRONT)
#define	AV_CHANNEL_LAYOUT_3POINT1POINT2   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_3POINT1POINT2)
#define	AV_CHANNEL_LAYOUT_HEXAGONAL   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_HEXAGONAL)
#define	AV_CHANNEL_LAYOUT_6POINT1   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_6POINT1)
#define	AV_CHANNEL_LAYOUT_6POINT1_BACK   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_6POINT1_BACK)
#define	AV_CHANNEL_LAYOUT_6POINT1_FRONT   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_6POINT1_FRONT)
#define	AV_CHANNEL_LAYOUT_7POINT0   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_7POINT0)
#define	AV_CHANNEL_LAYOUT_7POINT0_FRONT   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_7POINT0_FRONT)
#define	AV_CHANNEL_LAYOUT_7POINT1   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_7POINT1)
#define	AV_CHANNEL_LAYOUT_7POINT1_WIDE   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_7POINT1_WIDE)
#define	AV_CHANNEL_LAYOUT_7POINT1_WIDE_BACK   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_7POINT1_WIDE_BACK)
#define	AV_CHANNEL_LAYOUT_5POINT1POINT2_BACK   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_5POINT1POINT2_BACK)
#define	AV_CHANNEL_LAYOUT_OCTAGONAL   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_OCTAGONAL)
#define	AV_CHANNEL_LAYOUT_CUBE   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_CUBE)
#define	AV_CHANNEL_LAYOUT_5POINT1POINT4_BACK   AV_CHANNEL_LAYOUT_MASK(10, AV_CH_LAYOUT_5POINT1POINT4_BACK)
#define	AV_CHANNEL_LAYOUT_7POINT1POINT2   AV_CHANNEL_LAYOUT_MASK(10, AV_CH_LAYOUT_7POINT1POINT2)
#define	AV_CHANNEL_LAYOUT_7POINT1POINT4_BACK   AV_CHANNEL_LAYOUT_MASK(12, AV_CH_LAYOUT_7POINT1POINT4_BACK)
#define	AV_CHANNEL_LAYOUT_HEXADECAGONAL   AV_CHANNEL_LAYOUT_MASK(16, AV_CH_LAYOUT_HEXADECAGONAL)
#define	AV_CHANNEL_LAYOUT_STEREO_DOWNMIX   AV_CHANNEL_LAYOUT_MASK(2, AV_CH_LAYOUT_STEREO_DOWNMIX)
#define	AV_CHANNEL_LAYOUT_22POINT2   AV_CHANNEL_LAYOUT_MASK(24, AV_CH_LAYOUT_22POINT2)
#define	AV_CHANNEL_LAYOUT_7POINT1_TOP_BACK   AV_CHANNEL_LAYOUT_5POINT1POINT2_BACK
#define	AV_CHANNEL_LAYOUT_AMBISONIC_FIRST_ORDER

Detailed Description

Audio channel layout utility functions.

Macro Definition Documentation

AV_CHANNEL_LAYOUT_MASK

#define AV_CHANNEL_LAYOUT_MASK	(		nb,
			m
	)

Value:

    { /* .order */ AV_CHANNEL_ORDER_NATIVE, \
      /* .nb_channels */  (nb), \
      /* .u.mask */ { m }, \
      /* .opaque */ NULL }

Macro to define native channel layouts.

Note

This doesn't use designated initializers for compatibility with C++ 17 and older.

Definition at line 372 of file channel_layout.h.

AV_CHANNEL_LAYOUT_MONO

#define AV_CHANNEL_LAYOUT_MONO   AV_CHANNEL_LAYOUT_MASK(1, AV_CH_LAYOUT_MONO)

Definition at line 382 of file channel_layout.h.

AV_CHANNEL_LAYOUT_STEREO

#define AV_CHANNEL_LAYOUT_STEREO   AV_CHANNEL_LAYOUT_MASK(2, AV_CH_LAYOUT_STEREO)

Examples

encode_audio.c, mux.c, and resample_audio.c.

Definition at line 383 of file channel_layout.h.

AV_CHANNEL_LAYOUT_2POINT1

#define AV_CHANNEL_LAYOUT_2POINT1   AV_CHANNEL_LAYOUT_MASK(3, AV_CH_LAYOUT_2POINT1)

Definition at line 384 of file channel_layout.h.

AV_CHANNEL_LAYOUT_2_1

#define AV_CHANNEL_LAYOUT_2_1   AV_CHANNEL_LAYOUT_MASK(3, AV_CH_LAYOUT_2_1)

Definition at line 385 of file channel_layout.h.

AV_CHANNEL_LAYOUT_SURROUND

#define AV_CHANNEL_LAYOUT_SURROUND   AV_CHANNEL_LAYOUT_MASK(3, AV_CH_LAYOUT_SURROUND)

Examples

resample_audio.c.

Definition at line 386 of file channel_layout.h.

AV_CHANNEL_LAYOUT_3POINT1

#define AV_CHANNEL_LAYOUT_3POINT1   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_3POINT1)

Definition at line 387 of file channel_layout.h.

AV_CHANNEL_LAYOUT_4POINT0

#define AV_CHANNEL_LAYOUT_4POINT0   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_4POINT0)

Definition at line 388 of file channel_layout.h.

AV_CHANNEL_LAYOUT_4POINT1

#define AV_CHANNEL_LAYOUT_4POINT1   AV_CHANNEL_LAYOUT_MASK(5, AV_CH_LAYOUT_4POINT1)

Definition at line 389 of file channel_layout.h.

AV_CHANNEL_LAYOUT_2_2

#define AV_CHANNEL_LAYOUT_2_2   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_2_2)

Definition at line 390 of file channel_layout.h.

AV_CHANNEL_LAYOUT_QUAD

#define AV_CHANNEL_LAYOUT_QUAD   AV_CHANNEL_LAYOUT_MASK(4, AV_CH_LAYOUT_QUAD)

Definition at line 391 of file channel_layout.h.

AV_CHANNEL_LAYOUT_5POINT0

#define AV_CHANNEL_LAYOUT_5POINT0   AV_CHANNEL_LAYOUT_MASK(5, AV_CH_LAYOUT_5POINT0)

Definition at line 392 of file channel_layout.h.

AV_CHANNEL_LAYOUT_5POINT1

#define AV_CHANNEL_LAYOUT_5POINT1   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_5POINT1)

Definition at line 393 of file channel_layout.h.

AV_CHANNEL_LAYOUT_5POINT0_BACK

#define AV_CHANNEL_LAYOUT_5POINT0_BACK   AV_CHANNEL_LAYOUT_MASK(5, AV_CH_LAYOUT_5POINT0_BACK)

Definition at line 394 of file channel_layout.h.

AV_CHANNEL_LAYOUT_5POINT1_BACK

#define AV_CHANNEL_LAYOUT_5POINT1_BACK   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_5POINT1_BACK)

Definition at line 395 of file channel_layout.h.

AV_CHANNEL_LAYOUT_6POINT0

#define AV_CHANNEL_LAYOUT_6POINT0   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_6POINT0)

Definition at line 396 of file channel_layout.h.

AV_CHANNEL_LAYOUT_6POINT0_FRONT

#define AV_CHANNEL_LAYOUT_6POINT0_FRONT   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_6POINT0_FRONT)

Definition at line 397 of file channel_layout.h.

AV_CHANNEL_LAYOUT_3POINT1POINT2

#define AV_CHANNEL_LAYOUT_3POINT1POINT2   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_3POINT1POINT2)

Definition at line 398 of file channel_layout.h.

AV_CHANNEL_LAYOUT_HEXAGONAL

#define AV_CHANNEL_LAYOUT_HEXAGONAL   AV_CHANNEL_LAYOUT_MASK(6, AV_CH_LAYOUT_HEXAGONAL)

Definition at line 399 of file channel_layout.h.

AV_CHANNEL_LAYOUT_6POINT1

#define AV_CHANNEL_LAYOUT_6POINT1   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_6POINT1)

Definition at line 400 of file channel_layout.h.

AV_CHANNEL_LAYOUT_6POINT1_BACK

#define AV_CHANNEL_LAYOUT_6POINT1_BACK   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_6POINT1_BACK)

Definition at line 401 of file channel_layout.h.

AV_CHANNEL_LAYOUT_6POINT1_FRONT

#define AV_CHANNEL_LAYOUT_6POINT1_FRONT   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_6POINT1_FRONT)

Definition at line 402 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT0

#define AV_CHANNEL_LAYOUT_7POINT0   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_7POINT0)

Definition at line 403 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT0_FRONT

#define AV_CHANNEL_LAYOUT_7POINT0_FRONT   AV_CHANNEL_LAYOUT_MASK(7, AV_CH_LAYOUT_7POINT0_FRONT)

Definition at line 404 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT1

#define AV_CHANNEL_LAYOUT_7POINT1   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_7POINT1)

Definition at line 405 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT1_WIDE

#define AV_CHANNEL_LAYOUT_7POINT1_WIDE   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_7POINT1_WIDE)

Definition at line 406 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT1_WIDE_BACK

#define AV_CHANNEL_LAYOUT_7POINT1_WIDE_BACK   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_7POINT1_WIDE_BACK)

Definition at line 407 of file channel_layout.h.

AV_CHANNEL_LAYOUT_5POINT1POINT2_BACK

#define AV_CHANNEL_LAYOUT_5POINT1POINT2_BACK   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_5POINT1POINT2_BACK)

Definition at line 408 of file channel_layout.h.

AV_CHANNEL_LAYOUT_OCTAGONAL

#define AV_CHANNEL_LAYOUT_OCTAGONAL   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_OCTAGONAL)

Definition at line 409 of file channel_layout.h.

AV_CHANNEL_LAYOUT_CUBE

#define AV_CHANNEL_LAYOUT_CUBE   AV_CHANNEL_LAYOUT_MASK(8, AV_CH_LAYOUT_CUBE)

Definition at line 410 of file channel_layout.h.

AV_CHANNEL_LAYOUT_5POINT1POINT4_BACK

#define AV_CHANNEL_LAYOUT_5POINT1POINT4_BACK   AV_CHANNEL_LAYOUT_MASK(10, AV_CH_LAYOUT_5POINT1POINT4_BACK)

Definition at line 411 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT1POINT2

#define AV_CHANNEL_LAYOUT_7POINT1POINT2   AV_CHANNEL_LAYOUT_MASK(10, AV_CH_LAYOUT_7POINT1POINT2)

Definition at line 412 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT1POINT4_BACK

#define AV_CHANNEL_LAYOUT_7POINT1POINT4_BACK   AV_CHANNEL_LAYOUT_MASK(12, AV_CH_LAYOUT_7POINT1POINT4_BACK)

Definition at line 413 of file channel_layout.h.

AV_CHANNEL_LAYOUT_HEXADECAGONAL

#define AV_CHANNEL_LAYOUT_HEXADECAGONAL   AV_CHANNEL_LAYOUT_MASK(16, AV_CH_LAYOUT_HEXADECAGONAL)

Definition at line 414 of file channel_layout.h.

AV_CHANNEL_LAYOUT_STEREO_DOWNMIX

#define AV_CHANNEL_LAYOUT_STEREO_DOWNMIX   AV_CHANNEL_LAYOUT_MASK(2, AV_CH_LAYOUT_STEREO_DOWNMIX)

Definition at line 415 of file channel_layout.h.

AV_CHANNEL_LAYOUT_22POINT2

#define AV_CHANNEL_LAYOUT_22POINT2   AV_CHANNEL_LAYOUT_MASK(24, AV_CH_LAYOUT_22POINT2)

Definition at line 416 of file channel_layout.h.

AV_CHANNEL_LAYOUT_7POINT1_TOP_BACK

#define AV_CHANNEL_LAYOUT_7POINT1_TOP_BACK   AV_CHANNEL_LAYOUT_5POINT1POINT2_BACK

Definition at line 418 of file channel_layout.h.

AV_CHANNEL_LAYOUT_AMBISONIC_FIRST_ORDER

#define AV_CHANNEL_LAYOUT_AMBISONIC_FIRST_ORDER

Value:

    { /* .order */ AV_CHANNEL_ORDER_AMBISONIC, \
      /* .nb_channels */ 4, \
      /* .u.mask */ { 0 }, \
      /* .opaque */ NULL }

Definition at line 420 of file channel_layout.h.

Enumeration Type Documentation

AVChannel

enum AVChannel

Enumerator
AV_CHAN_NONE	Invalid channel index.
AV_CHAN_FRONT_LEFT
AV_CHAN_FRONT_RIGHT
AV_CHAN_FRONT_CENTER
AV_CHAN_LOW_FREQUENCY
AV_CHAN_BACK_LEFT
AV_CHAN_BACK_RIGHT
AV_CHAN_FRONT_LEFT_OF_CENTER
AV_CHAN_FRONT_RIGHT_OF_CENTER
AV_CHAN_BACK_CENTER
AV_CHAN_SIDE_LEFT
AV_CHAN_SIDE_RIGHT
AV_CHAN_TOP_CENTER
AV_CHAN_TOP_FRONT_LEFT
AV_CHAN_TOP_FRONT_CENTER
AV_CHAN_TOP_FRONT_RIGHT
AV_CHAN_TOP_BACK_LEFT
AV_CHAN_TOP_BACK_CENTER
AV_CHAN_TOP_BACK_RIGHT
AV_CHAN_STEREO_LEFT	Stereo downmix.
AV_CHAN_STEREO_RIGHT	See above.
AV_CHAN_WIDE_LEFT
AV_CHAN_WIDE_RIGHT
AV_CHAN_SURROUND_DIRECT_LEFT
AV_CHAN_SURROUND_DIRECT_RIGHT
AV_CHAN_LOW_FREQUENCY_2
AV_CHAN_TOP_SIDE_LEFT
AV_CHAN_TOP_SIDE_RIGHT
AV_CHAN_BOTTOM_FRONT_CENTER
AV_CHAN_BOTTOM_FRONT_LEFT
AV_CHAN_BOTTOM_FRONT_RIGHT
AV_CHAN_UNUSED	Channel is empty can be safely skipped.
AV_CHAN_UNKNOWN	Channel contains data, but its position is unknown.
AV_CHAN_AMBISONIC_BASE	Range of channels between AV_CHAN_AMBISONIC_BASE and AV_CHAN_AMBISONIC_END represent Ambisonic components using the ACN system. Given a channel id <i> between AV_CHAN_AMBISONIC_BASE and AV_CHAN_AMBISONIC_END (inclusive), the ACN index of the channel <n> is <n> = <i> - AV_CHAN_AMBISONIC_BASE. Note these values are only used for AV_CHANNEL_ORDER_CUSTOM channel orderings, the AV_CHANNEL_ORDER_AMBISONIC ordering orders the channels implicitly by their position in the stream.
AV_CHAN_AMBISONIC_END

Definition at line 47 of file channel_layout.h.

AVChannelOrder

enum AVChannelOrder

Enumerator
AV_CHANNEL_ORDER_UNSPEC	Only the channel count is specified, without any further information about the channel order.
AV_CHANNEL_ORDER_NATIVE	The native channel order, i.e. the channels are in the same order in which they are defined in the AVChannel enum. This supports up to 63 different channels.
AV_CHANNEL_ORDER_CUSTOM	The channel order does not correspond to any other predefined order and is stored as an explicit map. For example, this could be used to support layouts with 64 or more channels, or with empty/skipped (AV_CHAN_SILENCE) channels at arbitrary positions.
AV_CHANNEL_ORDER_AMBISONIC	The audio is represented as the decomposition of the sound field into spherical harmonics. Each channel corresponds to a single expansion component. Channels are ordered according to ACN (Ambisonic Channel Number). The channel with the index n in the stream contains the spherical harmonic of degree l and order m given by l = floor(sqrt(n)), m = n - l * (l + 1). Conversely given a spherical harmonic of degree l and order m, the corresponding channel index n is given by n = l * (l + 1) + m. Normalization is assumed to be SN3D (Schmidt Semi-Normalization) as defined in AmbiX format $ 2.1.

Definition at line 107 of file channel_layout.h.

Function Documentation

av_channel_name()

int av_channel_name	(	char *	buf,
		size_t	buf_size,
		enum AVChannel	channel
	)

Get a human readable string in an abbreviated form describing a given channel.

This is the inverse function of av_channel_from_string().

Parameters

buf	pre-allocated buffer where to put the generated string
buf_size	size in bytes of the buffer.
channel	the AVChannel whose name to get

Returns

amount of bytes needed to hold the output string, or a negative AVERROR on failure. If the returned value is bigger than buf_size, then the string was truncated.

av_channel_name_bprint()

void av_channel_name_bprint	(	struct AVBPrint *	bp,
		enum AVChannel	channel_id
	)

bprint variant of av_channel_name().

Note

the string will be appended to the bprint buffer.

av_channel_description()

int av_channel_description	(	char *	buf,
		size_t	buf_size,
		enum AVChannel	channel
	)

Get a human readable string describing a given channel.

Parameters

buf	pre-allocated buffer where to put the generated string
buf_size	size in bytes of the buffer.
channel	the AVChannel whose description to get

Returns

amount of bytes needed to hold the output string, or a negative AVERROR on failure. If the returned value is bigger than buf_size, then the string was truncated.

av_channel_description_bprint()

void av_channel_description_bprint	(	struct AVBPrint *	bp,
		enum AVChannel	channel_id
	)

bprint variant of av_channel_description().

Note

the string will be appended to the bprint buffer.

av_channel_from_string()

enum AVChannel av_channel_from_string

(

const char *

name

)

This is the inverse function of av_channel_name().

Returns

the channel with the given name AV_CHAN_NONE when name does not identify a known channel

av_channel_layout_from_mask()

int av_channel_layout_from_mask	(	AVChannelLayout *	channel_layout,
		uint64_t	mask
	)

Initialize a native channel layout from a bitmask indicating which channels are present.

Parameters

channel_layout	the layout structure to be initialized
mask	bitmask describing the channel layout

Returns

0 on success AVERROR(EINVAL) for invalid mask values

av_channel_layout_from_string()

int av_channel_layout_from_string	(	AVChannelLayout *	channel_layout,
		const char *	str
	)

Initialize a channel layout from a given string description.

The input string can be represented by:

• the formal channel layout name (returned by av_channel_layout_describe())
• single or multiple channel names (returned by av_channel_name(), eg. "FL", or concatenated with "+", each optionally containing a custom name after a "@", eg. "FL@Left+FR@Right+LFE")
• a decimal or hexadecimal value of a native channel layout (eg. "4" or "0x4")
• the number of channels with default layout (eg. "4c")
• the number of unordered channels (eg. "4C" or "4 channels")
• the ambisonic order followed by optional non-diegetic channels (eg. "ambisonic 2+stereo")

Parameters

channel_layout	input channel layout
str	string describing the channel layout

Returns

0 channel layout was detected, AVERROR_INVALIDATATA otherwise

av_channel_layout_default()

void av_channel_layout_default	(	AVChannelLayout *	ch_layout,
		int	nb_channels
	)

Get the default channel layout for a given number of channels.

Parameters

ch_layout	the layout structure to be initialized
nb_channels	number of channels

Examples

decode_filter_audio.c, transcode.c, and transcode_aac.c.

Referenced by init_filter(), init_filters(), and open_output_file().

av_channel_layout_standard()

const AVChannelLayout * av_channel_layout_standard

(

void **

opaque

)

Iterate over all standard channel layouts.

Parameters

opaque

a pointer where libavutil will store the iteration state. Must point to NULL to start the iteration.

Returns

the standard channel layout or NULL when the iteration is finished

av_channel_layout_uninit()

void av_channel_layout_uninit

(

AVChannelLayout *

channel_layout

)

Free any allocated data in the channel layout and reset the channel count to 0.

Parameters

channel_layout

the layout structure to be uninitialized

av_channel_layout_copy()

int av_channel_layout_copy	(	AVChannelLayout *	dst,
		const AVChannelLayout *	src
	)

Make a copy of a channel layout.

This differs from just assigning src to dst in that it allocates and copies the map for AV_CHANNEL_ORDER_CUSTOM.

Note

the destination channel_layout will be always uninitialized before copy.

Parameters

dst	destination channel layout
src	source channel layout

Returns

0 on success, a negative AVERROR on error.

Examples

encode_audio.c, filter_audio.c, mux.c, transcode.c, and transcode_aac.c.

Referenced by add_stream(), alloc_audio_frame(), get_input(), init_output_frame(), main(), open_output_file(), and select_channel_layout().

av_channel_layout_describe()

int av_channel_layout_describe	(	const AVChannelLayout *	channel_layout,
		char *	buf,
		size_t	buf_size
	)

Get a human-readable string describing the channel layout properties.

The string will be in the same format that is accepted by av_channel_layout_from_string(), allowing to rebuild the same channel layout, except for opaque pointers.

Parameters

channel_layout	channel layout to be described
buf	pre-allocated buffer where to put the generated string
buf_size	size in bytes of the buffer.

Returns

amount of bytes needed to hold the output string, or a negative AVERROR on failure. If the returned value is bigger than buf_size, then the string was truncated.

Examples

decode_filter_audio.c, filter_audio.c, resample_audio.c, and transcode.c.

Referenced by init_filter(), init_filter_graph(), init_filters(), and main().

av_channel_layout_describe_bprint()

int av_channel_layout_describe_bprint	(	const AVChannelLayout *	channel_layout,
		struct AVBPrint *	bp
	)

bprint variant of av_channel_layout_describe().

Note

the string will be appended to the bprint buffer.

Returns

0 on success, or a negative AVERROR value on failure.

av_channel_layout_channel_from_index()

enum AVChannel av_channel_layout_channel_from_index	(	const AVChannelLayout *	channel_layout,
		unsigned int	idx
	)

Get the channel with the given index in a channel layout.

Parameters

channel_layout	input channel layout
idx	index of the channel

Returns

channel with the index idx in channel_layout on success or AV_CHAN_NONE on failure (if idx is not valid or the channel order is unspecified)

av_channel_layout_index_from_channel()

int av_channel_layout_index_from_channel	(	const AVChannelLayout *	channel_layout,
		enum AVChannel	channel
	)

Get the index of a given channel in a channel layout.

In case multiple channels are found, only the first match will be returned.

Parameters

channel_layout	input channel layout
channel	the channel whose index to obtain

Returns

index of channel in channel_layout on success or a negative number if channel is not present in channel_layout.

av_channel_layout_index_from_string()

int av_channel_layout_index_from_string	(	const AVChannelLayout *	channel_layout,
		const char *	name
	)

Get the index in a channel layout of a channel described by the given string.

In case multiple channels are found, only the first match will be returned.

This function accepts channel names in the same format as av_channel_from_string().

Parameters

channel_layout	input channel layout
name	string describing the channel whose index to obtain

Returns

a channel index described by the given string, or a negative AVERROR value.

av_channel_layout_channel_from_string()

enum AVChannel av_channel_layout_channel_from_string	(	const AVChannelLayout *	channel_layout,
		const char *	name
	)

Get a channel described by the given string.

This function accepts channel names in the same format as av_channel_from_string().

Parameters

channel_layout	input channel layout
name	string describing the channel to obtain

Returns

a channel described by the given string in channel_layout on success or AV_CHAN_NONE on failure (if the string is not valid or the channel order is unspecified)

av_channel_layout_subset()

uint64_t av_channel_layout_subset	(	const AVChannelLayout *	channel_layout,
		uint64_t	mask
	)

Find out what channels from a given set are present in a channel layout, without regard for their positions.

Parameters

channel_layout	input channel layout
mask	a combination of AV_CH_* representing a set of channels

Returns

a bitfield representing all the channels from mask that are present in channel_layout

av_channel_layout_check()

int av_channel_layout_check

(

const AVChannelLayout *

channel_layout

)

Check whether a channel layout is valid, i.e.

can possibly describe audio data.

Parameters

channel_layout

input channel layout

Returns

1 if channel_layout is valid, 0 otherwise.

av_channel_layout_compare()

int av_channel_layout_compare	(	const AVChannelLayout *	chl,
		const AVChannelLayout *	chl1
	)

Check whether two channel layouts are semantically the same, i.e.

the same channels are present on the same positions in both.

If one of the channel layouts is AV_CHANNEL_ORDER_UNSPEC, while the other is not, they are considered to be unequal. If both are AV_CHANNEL_ORDER_UNSPEC, they are considered equal iff the channel counts are the same in both.

Parameters

chl	input channel layout
chl1	input channel layout

Returns

0 if chl and chl1 are equal, 1 if they are not equal. A negative AVERROR code if one or both are invalid.