av (version 0.9.2)

read_audio_fft: 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)))