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41 lines
828 B
41 lines
828 B
package mp3 |
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import "errors" |
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type Parser struct { |
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samplingFrequency int |
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} |
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func NewParser() *Parser { |
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return &Parser{} |
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} |
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// sampling_frequency - indicates the sampling frequency, according to the following table. |
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// '00' 44.1 kHz |
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// '01' 48 kHz |
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// '10' 32 kHz |
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// '11' reserved |
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var mp3Rates = []int{44100, 48000, 32000} |
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var ( |
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errMp3DataInvalid = errors.New("mp3data invalid") |
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errIndexInvalid = errors.New("invalid rate index") |
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) |
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func (self *Parser) Parse(src []byte) error { |
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if len(src) < 3 { |
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return errMp3DataInvalid |
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} |
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index := (src[2] >> 2) & 0x3 |
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if index <= byte(len(mp3Rates)-1) { |
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self.samplingFrequency = mp3Rates[index] |
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return nil |
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} |
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return errIndexInvalid |
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} |
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func (self *Parser) SampleRate() int { |
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if self.samplingFrequency == 0 { |
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self.samplingFrequency = 44100 |
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} |
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return self.samplingFrequency |
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}
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