read_audio: Read audio binary and frequency data

In av: Working with Audio and Video in R

Read audio binary and frequency data

Description

Reads raw audio data from any common audio or video format. Use read_audio_bin to get raw PCM audio samples, or read_audio_fft to stream-convert directly into frequency domain (spectrum) data using FFmpeg built-in FFT.

Usage

read_audio_fft(
  audio,
  window = hanning(1024),
  overlap = 0.75,
  sample_rate = NULL,
  start_time = NULL,
  end_time = NULL
)

read_audio_bin(
  audio,
  channels = NULL,
  sample_rate = NULL,
  start_time = NULL,
  end_time = NULL
)

write_audio_bin(
  pcm_data,
  pcm_channels = 1L,
  pcm_format = "s32le",
  output = "output.mp3",
  ...
)

Arguments

audio	path to the input sound or video file containing the audio stream
window	vector with weights defining the moving fft window function. The length of this vector is the size of the window and hence determines the output frequency range.
overlap	value between 0 and 1 of overlap proportion between moving fft windows
sample_rate	downsample audio to reduce FFT output size. Default keeps sample rate from the input file.
start_time, end_time	position (in seconds) to cut input stream to be processed.
channels	number of output channels, set to 1 to convert to mono sound
pcm_data	integer vector as returned by read_audio_bin
pcm_channels	number of channels in the data. Use the same value as you entered in read_audio_bin.
pcm_format	this is always s32le (signed 32-bit integer) for now
output	passed to av_audio_convert
...	other paramters for av_audio_convert

Details

Currently read_audio_fft automatically converts input audio to mono channel such that we get a single matrix. Use the plot() method on data returned by read_audio_fft to show the spectrogram. The av_spectrogram_video generates a video that plays the audio while showing an animated spectrogram with moving status bar, which is very cool.

See Also

Other av: capturing, demo(), encoding, formats, info, logging

Examples

# Use a 5 sec fragment
wonderland <- system.file('samples/Synapsis-Wonderland.mp3', package='av')

# Read initial 5 sec as as frequency spectrum
fft_data <- read_audio_fft(wonderland, end_time = 5.0)
dim(fft_data)

# Plot the spectrogram
plot(fft_data)

# Show other parameters
dim(read_audio_fft(wonderland, end_time = 5.0, hamming(2048)))
dim(read_audio_fft(wonderland, end_time = 5.0, hamming(4096)))

av documentation built on Oct. 4, 2024, 5:08 p.m.