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73 lines
1.9 KiB
Go
73 lines
1.9 KiB
Go
package mpeg
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// https://wiki.multimedia.cx/index.php/MPEG-4_Audio
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import (
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"fq/format"
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"fq/format/registry"
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"fq/pkg/decode"
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)
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func init() {
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registry.MustRegister(&decode.Format{
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Name: format.MPEG_ASC,
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Description: "MPEG-4 Audio Specific Config",
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DecodeFn: ascDecoder,
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})
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}
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var frequencyIndexHz = map[uint64]int{
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0x0: 96000,
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0x1: 88200,
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0x2: 64000,
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0x3: 48000,
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0x4: 44100,
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0x5: 32000,
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0x6: 24000,
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0x7: 22050,
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0x8: 16000,
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0x9: 12000,
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0xa: 11025,
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0xb: 8000,
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0xc: 7350,
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0xd: -1,
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0xe: -1,
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0xf: -1,
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}
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var channelConfigurationNames = map[uint64]string{
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0: "Defined in AOT Specifc Config",
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1: "channel: front-center",
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2: "channels: front-left, front-right",
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3: "channels: front-center, front-left, front-right",
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4: "channels: front-center, front-left, front-right, back-center",
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5: "channels: front-center, front-left, front-right, back-left, back-right",
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6: "channels: front-center, front-left, front-right, back-left, back-right, LFE-channel",
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7: "channels: front-center, front-left, front-right, side-left, side-right, back-left, back-right, LFE-channel",
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}
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func ascDecoder(d *decode.D, in interface{}) interface{} {
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objectType, _ := d.FieldStringMapFn("object_type", format.MPEGAudioObjectTypeNames, "Unknown", func() uint64 {
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n := d.U5()
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if n == 31 {
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n = 32 + d.U6()
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}
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return n
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}, decode.NumberDecimal)
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d.FieldUFn("frequency_index", func() (uint64, decode.DisplayFormat, string) {
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v := d.U4()
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if v == 15 {
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return d.U24(), decode.NumberDecimal, ""
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}
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if f, ok := frequencyIndexHz[v]; ok {
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return uint64(f), decode.NumberDecimal, ""
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}
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return 0, decode.NumberDecimal, "Invalid"
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})
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d.FieldStringMapFn("channel_configuration", channelConfigurationNames, "Reserved", d.U4, decode.NumberDecimal)
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// TODO: GASpecificConfig etc
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d.FieldBitBufLen("var_aot_or_byte_align", d.BitsLeft())
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return format.MPEGASCOut{ObjectType: int(objectType)}
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}
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