README
¶
GAAD (Go Advanced Audio Decoder)
Package currently provides AAC parsing capabilities. This package performs a full parse of AAC-LC and HE-AACv1 bitstreams. Bitstreams with Parametric Stereo (HE-AACv2) are not yet supported, but AAC bitstream data and SBR data will be extracted. The AAC decode from the parsed data to LPCM (.wav) is not yet implemented. Please help us expand and test this library!
AACParser
This package currently supports AAC audio data contained in an ADTS header. All available data is returned in the adts struct and can be accessed as nested objects as presented in the AAC specification. All parameter names should be verbatim from the AAC specification, if you find an issue with this please file a bug or submit a pull request.
AAC Types
| Type | Description | CODEC |
|---|---|---|
| AACLC | AAC | mp4a.40.2 |
| HEAAC | AAC + SBR | mp4a.40.5 |
| HEAACv2 | AAC + SBR + PS | mp4a.40.29 |
where:
- SBR = Spectral band replication
- PS = Parametric Stereo
Usage
var []byte buf
buf = <ADTS+AAC data>
// Parsing the buffer
adts, err := gaad.ParseADTS(buf)
// Looping through top level elements and accessing sub-elements
var sbr bool
if adts.Fill_elements != nil {
for _, e := range adts.Fill_elements {
if e.Extension_payload != nil &&
e.Extension_payload.Extension_type == gaad.EXT_SBR_DATA {
sbr = true
}
}
}
VBR vs CBR
VBR (Variable bitrate) and CBR (Constant bitrate) is derived from the bitstream_type attribute in the adif_header section. It is VBR if bitstream_type is true, and CBR otherwise.
References
ISO/IEC STANDARD 14496-3
Title : Coding of audio-visual objects — Part 3: Audio
File : ISO_14496-3-4th-Edition.pdf
Edition : Fourth edition (2009-09-01)
Relevant Sections
- Page 64 : 1.6.5 Signaling of SBR
- Page 120 : 1.A.2 AAC Interchange formats
- Page 489 : 4.4.2 GA bitstream payloads
Related Books
- Video Demystified (5th Edition) http://my.safaribooksonline.com/book/-/9780750683951
Related Links
Documentation
¶
Index ¶
Constants ¶
const ( ID_SCE = 0x00 // "Single Channel Element" ID_CPE = 0x01 // "Channel Pair Element" ID_CCE = 0x02 // "Coupling Channel Element" ID_LFE = 0x03 // "LFE Channel Element" ID_DSE = 0x04 // "Data Stream Element" ID_PCE = 0x05 // "Program Config Element" ID_FIL = 0x06 // "Fill Element" ID_END = 0x07 // "End" )
////////////////////////////////////////////////////////////////////////////// ID_SYN_ELE (Syntactic Element) //////////////////////////////////////////////////////////////////////////////
const ( AUDIO_OBJECT_TYPE_NULL uint8 = 0 AUDIO_OBJECT_TYPE_AAC_MAIN = 1 AUDIO_OBJECT_TYPE_AAC_LC = 2 AUDIO_OBJECT_TYPE_SSR = 3 AUDIO_OBJECT_TYPE_LTP = 4 AUDIO_OBJECT_TYPE_SBR = 5 AUDIO_OBJECT_TYPE_AAC_SCALABLE = 6 AUDIO_OBJECT_TYPE_TWINVQ = 7 AUDIO_OBJECT_TYPE_CELP = 8 AUDIO_OBJECT_TYPE_HXVC = 9 AUDIO_OBJECT_TYPE_TTSI = 12 AUDIO_OBJECT_TYPE_MAIN_SYNTHESIS = 13 AUDIO_OBJECT_TYPE_WAVETABLE_SYNTHESIS = 14 AUDIO_OBJECT_TYPE_GENERAL_MIDI = 15 AUDIO_OBJECT_TYPE_ASAE = 16 AUDIO_OBJECT_TYPE_ER = 17 AUDIO_OBJECT_TYPE_ER_AAC_LTP = 19 AUDIO_OBJECT_TYPE_ER_AAC_SCALABLE = 20 AUDIO_OBJECT_TYPE_ER_TWINVQ = 21 AUDIO_OBJECT_TYPE_ER_BSAC = 22 AUDIO_OBJECT_TYPE_ER_AAC_LD = 23 AUDIO_OBJECT_TYPE_ER_CELP = 24 AUDIO_OBJECT_TYPE_ER_HVXC = 25 AUDIO_OBJECT_TYPE_ER_HILN = 26 AUDIO_OBJECT_TYPE_ER_PARAMETRIC = 27 AUDIO_OBJECT_TYPE_SSC = 28 AUDIO_OBJECT_TYPE_PS = 29 AUDIO_OBJECT_TYPE_MPEG_SURROUND = 30 AUDIO_OBJECT_TYPE_LAYER_1 = 32 AUDIO_OBJECT_TYPE_LAYER_2 = 33 AUDIO_OBJECT_TYPE_LAYER_3 = 34 AUDIO_OBJECT_TYPE_DST = 35 AUDIO_OBJECT_TYPE_ALS = 36 AUDIO_OBJECT_TYPE_SLS = 37 AUDIO_OBJECT_TYPE_SLS_NON_CORE = 38 AUDIO_OBJECT_TYPE_ER_AAC_ELD = 39 AUDIO_OBJECT_TYPE_SMR = 40 AUDIO_OBJECT_TYPE_SMR_MAIN = 41 AUDIO_OBJECT_TYPE_USAC_NO_SBR = 42 AUDIO_OBJECT_TYPE_SAOC = 43 AUDIO_OBJECT_TYPE_LD_MPEG_SURROUND = 44 AUDIO_OBJECT_TYPE_USAC = 45 )
////////////////////////////////////////////////////////////////////////////// Table 1.17 – Audio Object Types //////////////////////////////////////////////////////////////////////////////
const ( FIXFIX = 0 FIXVAR = 1 VARFIX = 2 VARVAR = 3 )
////////////////////////////////////////////////////////////////////////////// Table 4.114 – Values of the extension_type field //////////////////////////////////////////////////////////////////////////////
const ( EXT_FILL = 0x00 // ‘0000’ bitstream payload filler EXT_FILL_DATA = 0x01 // ‘0001’ bitstream payload data as filler EXT_DATA_ELEMENT = 0x02 // ’0010‘ data element EXT_DYNAMIC_RANGE = 0x0b // ‘1011’ dynamic range control EXT_SAC_DATA = 0x0c // ‘1100’ MPEG Surround EXT_SBR_DATA = 0x0d // ‘1101’ SBR enhancement EXT_SBR_DATA_CRC = 0x0e // ‘1110’ SBR enhancement with CRC )
////////////////////////////////////////////////////////////////////////////// Table 4.121 – Values of the extension_type field //////////////////////////////////////////////////////////////////////////////
const ( ONLY_LONG_SEQUENCE = 0 LONG_START_SEQUENCE = 1 EIGHT_SHORT_SEQUENCE = 2 LONG_STOP_SEQUENCE = 3 )
////////////////////////////////////////////////////////////////////////////// AAC WINDOW SEQUENCE //////////////////////////////////////////////////////////////////////////////
const ( MPEG_VERSION_4 = 0 MPEG_VERSION_2 = 1 )
////////////////////////////////////////////////////////////////////////////// MPEG VERSION //////////////////////////////////////////////////////////////////////////////
const ( /* The noiseless coding tool requires these constants (see Table 4.56). */ ZERO_HCB = 0 FIRST_PAIR_HCB = 5 ESC_HCB = 11 QUAD_LEN = 4 PAIR_LEN = 2 NOISE_HCB = 13 INTENSITY_HCB2 = 14 INTENSITY_HCB = 15 ESC_FLAG = 16 )
////////////////////////////////////////////////////////////////////////////// AAC WINDOW SEQUENCE //////////////////////////////////////////////////////////////////////////////
const (
ANC_DATA = 0x00 // ‘0000‘ Ancillary data element
)
////////////////////////////////////////////////////////////////////////////// Table 4.122 – Values of the data_element_version //////////////////////////////////////////////////////////////////////////////
const (
EXTENSION_ID_PS = 2
)
////////////////////////////////////////////////////////////////////////////// Table 4.121 – Values of the extension_type field //////////////////////////////////////////////////////////////////////////////
const (
MAX_LTP_LONG_SFB uint8 = 40
)
////////////////////////////////////////////////////////////////////////////// 4.6.7.2 - Long Term Prediction (LTP) definitions //////////////////////////////////////////////////////////////////////////////
const MaxBitsLeft = 131072
Variables ¶
var AACProfileType = [...]string{
"0: Null",
"1: AAC Main",
"2: AAC LC (Low Complexity)",
"3: AAC SSR (Scalable Sample Rate)",
"4: AAC LTP (Long Term Prediction)",
"5: SBR (Spectral Band Replication)",
"6: AAC Scalable",
"7: TwinVQ",
"8: CELP (Code Excited Linear Prediction)",
"9: HXVC (Harmonic Vector eXcitation Coding)",
"10: Reserved",
"11: Reserved",
"12: TTSI (Text-To-Speech Interface)",
"13: Main Synthesis",
"14: Wavetable Synthesis",
"15: General MIDI",
"16: Algorithmic Synthesis and Audio Effects",
"17: ER (Error Resilient) AAC LC",
"18: Reserved",
"19: ER AAC LTP",
"20: ER AAC Scalable",
"21: ER TwinVQ",
"22: ER BSAC (Bit-Sliced Arithmetic Coding)",
"23: ER AAC LD (Low Delay)",
"24: ER CELP",
"25: ER HVXC",
"26: ER HILN (Harmonic and Individual Lines plus Noise)",
"27: ER Parametric",
"28: SSC (SinuSoidal Coding)",
"29: PS (Parametric Stereo)",
"30: MPEG Surround",
"31: (Escape value)",
"32: Layer-1",
"33: Layer-2",
"34: Layer-3",
"35: DST (Direct Stream Transfer)",
"36: ALS (Audio Lossless)",
"37: SLS (Scalable LosslesS)",
"38: SLS non-core",
"39: ER AAC ELD (Enhanced Low Delay)",
"40: SMR (Symbolic Music Representation) Simple",
"41: SMR Main",
"42: USAC (Unified Speech and Audio Coding) (no SBR)",
"43: SAOC (Spatial Audio Object Coding)",
"44: LD MPEG Surround",
"45: USAC",
}
var Aac_PRED_SFB_MAX = [...]uint8{
33, 33, 38, 40, 40, 40, 41, 41, 37, 37, 37, 34, 64, 64, 64, 64,
}
var ChannelConfiguration = [...]string{
" 0: Defined in AOT Specifc Config",
" 1: 1 channel: front-center",
" 2: 2 channels: front-left, front-right",
" 3: 3 channels: front-center, front-left, front-right",
" 4: 4 channels: front-center, front-left, front-right, back-center",
" 5: 5 channels: front-center, front-left, front-right, back-left, back-right",
" 6: 6 channels: front-center, front-left, front-right, back-left, back-right, LFE-channel",
" 7: 8 channels: front-center, front-left, front-right, side-left, side-right, back-left, back-right, LFE-channel",
" 8: Reserved",
" 9: Reserved",
"10: Reserved",
"11: Reserved",
"12: Reserved",
"13: Reserved",
"14: Reserved",
"15: Reserved",
}
////////////////////////////////////////////////////////////////////////////// Table 1.19 – Channel Configuration //////////////////////////////////////////////////////////////////////////////
var SamplingFrequency = [...]uint32{
96000,
88200,
64000,
48000,
44100,
32000,
24000,
22050,
16000,
12000,
11025,
8000,
7350,
0,
0,
0,
}
////////////////////////////////////////////////////////////////////////////// Table 1.18 – Sampling Frequency Index //////////////////////////////////////////////////////////////////////////////
var SyntacticElement = [...]string{
"ID_SCE: Single Channel Element",
"ID_CPE: Channel Pair Element",
"ID_CCE: Coupling Channel Element",
"ID_LFE: LFE Channel Element",
"ID_DSE: Data Stream Element",
"ID_PCE: Program Config Element",
"ID_FIL: Fill Element",
"ID_END: End",
}
Functions ¶
This section is empty.
Types ¶
type ADTS ¶
type ADTS struct {
Bitrate uint32
ChannelConfiguration uint8
Layer uint8
MpegVersion uint8
Profile uint8
SamplingFrequency uint32
VbrMode bool
Frame_length uint16
Single_channel_elements []*single_channel_element
Channel_pair_elements []*channel_pair_element
Coupling_channel_elements []*coupling_channel_element
Lfe_channel_elements []*lfe_channel_element
Data_stream_elements []*data_stream_element
Program_config_elements []*program_config_element
Fill_elements []*fill_element
// contains filtered or unexported fields
}
Source Files
Directories