Audio::FindChunks 0.03

Audio::FindChunks can breaks audio files into sound/silence parts.

SYNOPSIS

use Audio::FindChunks;

# Duplicate input to output, caching RMS values to a file (as a side effect)
Audio::FindChunks->new(rms_filename => x.rms, filter => 1)->get(rms_data);

# Output human-readable info, using RMS cache file xxx.rms if present:
Audio::FindChunks->new(cache_rms => 1, filename => xxx.mp3,
stem_strip_extension => 1)->output_blocks();

# Remove start/end silence (if longer than 0.2sec):
Audio::FindChunks->new(cache_rms => 1, filename => xxx.mp3,
min_actual_silence_sec => 1e100)->split_file();

# Split a multiple-sides tape recording
Audio::FindChunks->new(filename => xxx.mp3, min_actual_silence_sec => 11
)->split_file({verbose => 1});

Audio sequence is broken into parts which contain only noise ("gaps"), and parts with usable signal ("tracks").

The following configuration settings (and defaults) are supported:

# For getting PCM flow (and if averaging data is read from cache)
frequency => 44100, # If raw_pcm or override_header_info only
bytes_per_sample => 4, # likewise
channels => 2, # likewise
sizedata => MY_INF, # likewise (how many bytes of PCM to read)
out_fh => *STDOUT, # mirror WAV/PCM to this FH if filter
# Process non-WAV data:
preprocess => {mp3 => [[qw(lame --silent --decode)], [], [-]]}, # Second contains extra args to read stdin
# RMS cache (used if valid_rms)
rms_extension => .rms, # Appended to the filestem
# Averaging to RMS info
sec_per_chunk => 0.1, # The window for taking mean square
# thresholds picking from the list of sorted 3-medians of RMS data
threshold_in_sorted_min_rel => 0, # relative position of threashold_min
threshold_in_sorted_min_sec => 1, # shifted by this amount in the list
threshold_factor_min => 1, # the list elt is multiplied by this
threshold_in_sorted_max_rel => 0.5, # likewise
threshold_in_sorted_max_sec => 0, # likewise
threshold_factor_max => 1, # likewise
threshold_ratio => 0.15, # relative position between min/max
# Chunkification: smoothification
above_thres_window => 11, # in units of chunks
above_thres_window_rel => 0.25, # fractions of chunks above threshold
# in a window to make chunk signal
# Splitting into runs of signal/noise
max_tracks => 9999, # fail if more signal/noise runs
min_signal_sec => 5, # such runs of signal are forced
min_silence_sec => 2, # likewise
ignore_signal_sec => 1, # short runs of signal are ignored
min_silence_chunks_merge (see below) # and long resulting runs of silence
# are forced
# Calculate average signal in an interval "deeply inside" silence runs
local_level_ignore_pre_sec => 0.3, # offset the start of this interval
local_level_ignore_pre_rel => 0.02, # additional relative offset
local_level_ignore_post_sec => 0.3, # likewise for end of the interval
local_level_ignore_post_rel => 0.02, # likewise
# Enlargement of signal runs: attach consequent chunks with signal this much
# above this average over the neighbour silence run
local_threshold_factor => 1.05,
# Final enlargement of runs of signal
extend_track_end_sec => 0.5, # Unconditional enlargement
extend_track_begin_sec => 0.3, # likewise
min_boundary_silence_sec => 0.2, # Ignore short silence at start/end

Note that above_thres_window is the only value specified directly in units of chunks; the other *_sec may be optionally specified in units of chunks by setting the corresponding *_chunks value. Note also that this window should better be decreased if minimal allowed silence length parameters are decreased.

These values are mirrored from other values if not explicitly specified:

min_actual_silence_sec << min_silence_sec # Ignore short gaps
min_start_silence_sec << min_boundary_silence_sec # Same at start
min_end_silence_sec << min_boundary_silence_sec # Same at end
min_silence_chunks_merge << min_silence_chunks # See above

cache_rms_write <<< cache_rms # Boolean: write RMS cache
cache_rms_read <<< cache_rms # Boolean: read RMS cache (unless filter)

The following values default to undef:

filename # if undef, read data from STDIN
stem_strip_extension # Boolean: filestem has no extension
filter # If true, PCM data is mirrored to out_fh
rms_filename # Specify cache file explicitly
raw_pcm # The input has no WAV header
override_header_info # The user specified values override WAV header
cache_rms # Use cache file (see *_write, *_read above)
skip_medians # Boolean: do not calculate 3-medians
subchunk_size # Optimization of calculation of RMS; the
# best value depends on the processor cache