Audio Channel Layouts
AudioChannelDescription
Contains information describing a single channel.
typedef struct AudioChannelDescription {
AudioChannelLabel mChannelLabel;
UInt32 mChannelFlags;
Float32 mCoordinates[3];
} AudioChannelDescription;
Discussion
This structure is used by AudioChannelLayout to
describe the position of a speaker. The mChannelFlags data
member contains a “Channel Labels” value, while mChannelFlags marks which
coordinate system is in use. The position of the speaker is kept
in mCoordinates, as per the “Channel Flags” and “Channel Coordinates.”
Availability
- Available in Mac OS X v10.2 and later.
Declared In
CoreAudioTypes.h
AudioChannelLayout
Specifies the channel layout in files and hardware.
typedef struct AudioChannelLayout {
AudioChannelLayoutTag mChannelLayoutTag;
UInt32 mChannelBitmap;
UInt32 mNumberChannelDescriptions;
AudioChannelDescription mChannelDescriptions[1];
} AudioChannelLayout;
Discussion
This structure is used to keep track of the channel arrangements. A “Channel Layout Tags” value, stored in mChannelLayoutTag, signifies which layout scheme is in use, or, if the scheme is not available there, mChannelBitmap may contain a bitmap describing the layout. The bitmap is formed using “Channel Bitmaps.”
Availability
- Available in Mac OS X v10.2 and later.
Declared In
CoreAudioTypes.h
Defined Data Types
Typedefs are provided to help describe channel layouts.
typedef UInt32 AudioChannelLabel; |
typedef UInt32 AudioChannelLayoutTag; |
Channel Labels
Specifies which channel is described by an AudioChannelDescription.
Unknown/unused:
kAudioChannelLabel_Unknown = 0xFFFFFFFF |
kAudioChannelLabel_Unused = 0 |
Standard channels:
kAudioChannelLabel_Left = 1 |
kAudioChannelLabel_Right= 2 |
kAudioChannelLabel_Center = 3 |
kAudioChannelLabel_LFEScreen = 4 |
kAudioChannelLabel_LeftSurround = 5 |
kAudioChannelLabel_RightSurround = 6 |
kAudioChannelLabel_LeftCenter = 7 |
kAudioChannelLabel_RightCenter = 8 |
kAudioChannelLabel_CenterSurround = 9 |
kAudioChannelLabel_LeftSurroundDirect = 10 |
kAudioChannelLabel_RightSurroundDirect = 11 |
kAudioChannelLabel_TopCenterSurround = 12 |
kAudioChannelLabel_VerticalHeightLeft = 13 |
kAudioChannelLabel_VerticalHeightCenter = 14 |
kAudioChannelLabel_VerticalHeightRight = 15 |
kAudioChannelLabel_TopBackLeft = 16 |
kAudioChannelLabel_TopBackCenter = 17 |
kAudioChannelLabel_TopBackRight = 18 |
kAudioChannelLabel_RearSurroundLeft = 33 |
kAudioChannelLabel_RearSurroundRight = 34 |
kAudioChannelLabel_LeftWide = 35 |
kAudioChannelLabel_RightWide = 36 |
kAudioChannelLabel_LFE2 = 37 |
kAudioChannelLabel_LeftTotal = 38 |
kAudioChannelLabel_RightTotal = 39 |
kAudioChannelLabel_HearingImpaired = 40 |
kAudioChannelLabel_Narration = 41 |
kAudioChannelLabel_Mono = 42 |
kAudioChannelLabel_DialogCentricMix = 43 |
First order Ambisonic channels:
kAudioChannelLabel_Ambisonic_W = 200 |
kAudioChannelLabel_Ambisonic_X = 201 |
kAudioChannelLabel_Ambisonic_Y = 202 |
kAudioChannelLabel_Ambisonic_Z = 203 |
Mid/side Recording:
kAudioChannelLabel_MS_Mid = 204 |
kAudioChannelLabel_MS_Side = 205 |
X-Y Recording:
kAudioChannelLabel_XY_X = 206 |
kAudioChannelLabel_XY_Y = 207 |
Other channels:
kAudioChannelLabel_HeadphonesLeft = 301 |
kAudioChannelLabel_HeadphonesRight = 302 |
kAudioChannelLabel_ClickTrack = 304 |
kAudioChannelLabel_ForeignLanguage = 305 |
Channel Bitmaps
Used in the mChannelBitmap field
of an AudioChannelLayout to specify a custom
layout.
kAudioChannelBit_Left = (1L<<0) |
kAudioChannelBit_Right = (1L<<1) |
kAudioChannelBit_Center = (1L<<2) |
kAudioChannelBit_LFEScreen = (1L<<3) |
kAudioChannelBit_LeftSurround = (1L<<4) |
kAudioChannelBit_RightSurround = (1L<<5) |
kAudioChannelBit_LeftCenter = (1L<<6) |
kAudioChannelBit_RightCenter = (1L<<7) |
kAudioChannelBit_CenterSurround = (1L<<8) |
kAudioChannelBit_LeftSurroundDirect = (1L<<9) |
kAudioChannelBit_RightSurroundDirect = (1L<<10) |
kAudioChannelBit_TopCenterSurround = (1L<<11) |
kAudioChannelBit_VerticalHeightLeft = (1L<<12) |
kAudioChannelBit_VerticalHeightCenter = (1L<<13) |
kAudioChannelBit_VerticalHeightRight = (1L<<14) |
kAudioChannelBit_TopBackLeft = (1L<<15) |
kAudioChannelBit_TopBackCenter = (1L<<16) |
kAudioChannelBit_TopBackRight = (1L<<17) |
Channel Flags
Specifies which coordinate system is in use, and if the distances
are measured in meters; stored in mChannelFields in
an AudioChannelDescription instance.
kAudioChannelFlags_RectangularCoordinates = (1L<<0) |
kAudioChannelFlags_SphericalCoordinates = (1L<<1) |
kAudioChannelFlags_Meters = (1L<<2) |
Channel Coordinates
Specifies the meaning of indices of mCoordinates in AudioChannelDescription.
For rectangular coordinates:
kAudioChannelCoordinates_LeftRight = 0 |
kAudioChannelCoordinates_BackFront = 1 |
kAudioChannelCoordinates_DownUp = 2 |
For spherical coordinates:
kAudioChannelCoordinates_Azimuth = 0 |
kAudioChannelCoordinates_Elevation = 1 |
kAudioChannelCoordinates_Distance = 2 |
Channel Layout Tags
Specifies which channel layout is in use; stored in mChannelLayout in AudioChannelLayout.
Other/unknown:
kAudioChannelLayoutTag_UseChannelDescriptions = 0 |
kAudioChannelLayoutTag_UseChannelBitmap = 1 |
kAudioChannelLayoutTag_AllUnknown = 9 |
General layouts:
kAudioChannelLayoutTag_Mono = 100 |
kAudioChannelLayoutTag_Stereo = 101 |
kAudioChannelLayoutTag_StereoHeadphones = 2 |
kAudioChannelLayoutTag_MatrixStereo = 3 |
kAudioChannelLayoutTag_MidSide = 4 |
kAudioChannelLayoutTag_XY = 5 |
kAudioChannelLayoutTag_Binaural = 6 |
kAudioChannelLayoutTag_Quadraphonic = 7 |
kAudioChannelLayoutTag_Ambisonic_B_Format = 8 |
kAudioChannelLayoutTag_AudioUnit_5_0 = 107 |
MPEG defined layouts:
kAudioChannelLayoutTag_MPEG_1_0 = 100 |
kAudioChannelLayoutTag_MPEG_2_0 = 101 |
kAudioChannelLayoutTag_MPEG_3_0_A = 102 |
kAudioChannelLayoutTag_MPEG_3_0_B = 103 |
kAudioChannelLayoutTag_MPEG_4_0_A = 104 |
kAudioChannelLayoutTag_MPEG_4_0_B = 105 |
kAudioChannelLayoutTag_MPEG_5_0_A = 106 |
kAudioChannelLayoutTag_MPEG_5_0_B = 107 |
kAudioChannelLayoutTag_MPEG_5_0_C = 108 |
kAudioChannelLayoutTag_MPEG_5_0_D = 109 |
kAudioChannelLayoutTag_MPEG_5_1_A = 110 |
kAudioChannelLayoutTag_MPEG_5_1_B = 111 |
kAudioChannelLayoutTag_MPEG_5_1_C = 112 |
kAudioChannelLayoutTag_MPEG_5_1_D = 113 |
kAudioChannelLayoutTag_MPEG_6_1_A = 114 |
kAudioChannelLayoutTag_MPEG_7_1_A = 115 |
kAudioChannelLayoutTag_MPEG_7_1_B = 116 |
kAudioChannelLayoutTag_MPEG_7_1_C = 117 |
kAudioChannelLayoutTag_Emagic_Default_7_1 = 118 |
kAudioChannelLayoutTag_SMPTE_DTV = 119 |
ITU defined layouts:
kAudioChannelLayoutTag_ITU_1_0 = 100 |
kAudioChannelLayoutTag_ITU_2_0 = 101 |
kAudioChannelLayoutTag_ITU_2_1 = 120 |
kAudioChannelLayoutTag_ITU_2_2 = 121 |
kAudioChannelLayoutTag_ITU_3_0 = 102 |
kAudioChannelLayoutTag_ITU_3_1 = 104 |
kAudioChannelLayoutTag_ITU_3_2 = 106 |
kAudioChannelLayoutTag_ITU_3_2_1 = 110 |
kAudioChannelLayoutTag_ITU_3_4_1 = 117 |
DVD defined layouts:
kAudioChannelLayoutTag_DVD_0 = 100 |
kAudioChannelLayoutTag_DVD_1 = 101 |
kAudioChannelLayoutTag_DVD_2 = 120 |
kAudioChannelLayoutTag_DVD_3 = 121 |
kAudioChannelLayoutTag_DVD_4 = 122 |
kAudioChannelLayoutTag_DVD_5 = 123 |
kAudioChannelLayoutTag_DVD_6 = 124 |
kAudioChannelLayoutTag_DVD_7 = 102 |
kAudioChannelLayoutTag_DVD_8 = 104 |
kAudioChannelLayoutTag_DVD_9 = 106 |
kAudioChannelLayoutTag_DVD_10 = 125 |
kAudioChannelLayoutTag_DVD_11 = 126 |
kAudioChannelLayoutTag_DVD_12 = 110 |
kAudioChannelLayoutTag_DVD_13 = 104 |
kAudioChannelLayoutTag_DVD_14 = 106 |
kAudioChannelLayoutTag_DVD_15 = 125 |
kAudioChannelLayoutTag_DVD_16 = 126 |
kAudioChannelLayoutTag_DVD_17 = 110 |
kAudioChannelLayoutTag_DVD_18 = 127 |
kAudioChannelLayoutTag_DVD_19 = 107 |
kAudioChannelLayoutTag_DVD_20 = 111 |
Last updated: 2004-03-25
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