\(\text{LoadAudio}\)

You can use the \(\text{LoadAudio}\) function to load audio content from an audio file. Note that this function is included as part of the audiofile plug-in and requires the supplied libaudiofile library to operate.

You can use the \loadaudio backslash command to insert this function.

The following variants of this function are available:

  • \(\text{tuple } \text{LoadAudio} \left ( \text{<filename>} \right )\)

  • \(\text{tuple } \text{LoadAudio} \left ( \text{<filename>}, \text{<encoding>}, \text{<sample rate>}, \text{<number channels>} \right )\)

The \(\text{LoadAudio}\) function currently supports the following formats:

  • MPEG 1/2 Audio Layer III

  • Microsoft WAV format

  • Multiple raw audio formats

The \(\text{<filename>}\) parameter should be a text string holding the name of the audio file to be loaded.

The \(\text{<encoding>}\) parameter is used when loading raw audio files and is used to indicate how the audio data is encoded. Supported basic encoding formats are listed in Table 38.

Table 38 Supported Raw Audio Encoding Formats

Encoding

\(\text{<encoding>}\) parameter value

A-law

a-law

alaw

\(\mu\)-law (ITU-T Recommendation G.711)

\(\mu\)-law

\(\mu\text{law}\)

8-bit differential pulse code modulation (DPCM)

dpcm8

16-bit differential pulse code modulation (DPCM)

dpcm16

8-bit pulse code modulation (PCM)

pcm8

16-bit pulse code modulation (PCM)

pcm16

24-bit pulse code modulation (PCM)

pcm24

32-bit pulse code modulation (PCM)

pcm32

Single precision floating point (32-bits/value, little-endian)

float

By default, all integer PCM formats are signed, little-endian. For the integer PCM formats, you can include any of the modifiers listed in Table 39. Note that each modifier can only be included once.

Table 39 Supported PCM Format Modifiers

Function

Modifier

Data is in little-endian format (default)

le

little-endian

Data is in big-endian format

be

big-endian

Data is signed

signed

Data is unsigned

unsigned

The \(\text{<sample rate}\) and \(\text{<number channels>}\) parameters are required for all raw audio formats and indicates the sample rate, in Hertz and the number of audio channels.

The function returns a tuple containing the sample rate, in Hz, followed by one or more real row matrices holding the audio samples for each channel. Floating point formats will provide the values as stored in the file, generally 0dBFS. Integer file formats will be converted to floating point and rescaled to 0dBFS.

Figure 165 shows the basic use of the \(\text{LoadAudio}\) function.

../_images/load_audio_example.png

Figure 165 Example Use Of The LoadAudio Function