"""MoviePy audio reading with ffmpeg."""
import subprocess as sp
import warnings
import numpy as np
from moviepy.config import FFMPEG_BINARY
from moviepy.tools import cross_platform_popen_params, ffmpeg_escape_filename
from moviepy.video.io.ffmpeg_reader import ffmpeg_parse_infos
[docs]
class FFMPEG_AudioReader:
"""A class to read the audio in either video files or audio files
using ffmpeg. ffmpeg will read any audio and transform them into
raw data.
Parameters
----------
filename
Name of any video or audio file, like ``video.mp4`` or
``sound.wav`` etc.
buffersize
The size of the buffer to use. Should be bigger than the buffer
used by ``write_audiofile``
print_infos
Print the ffmpeg infos on the file being read (for debugging)
fps
Desired frames per second in the decoded signal that will be
received from ffmpeg
nbytes
Desired number of bytes (1,2,4) in the signal that will be
received from ffmpeg
"""
def __init__(
self,
filename,
buffersize,
decode_file=False,
print_infos=False,
fps=44100,
nbytes=2,
nchannels=2,
):
# TODO bring FFMPEG_AudioReader more in line with FFMPEG_VideoReader
# E.g. here self.pos is still 1-indexed.
# (or have them inherit from a shared parent class)
self.filename = filename
self.nbytes = nbytes
self.fps = fps
self.format = "s%dle" % (8 * nbytes)
self.codec = "pcm_s%dle" % (8 * nbytes)
self.nchannels = nchannels
infos = ffmpeg_parse_infos(filename, decode_file=decode_file)
self.duration = infos["duration"]
self.bitrate = infos["audio_bitrate"]
self.infos = infos
self.proc = None
self.n_frames = int(self.fps * self.duration)
self.buffersize = min(self.n_frames + 1, buffersize)
self.buffer = None
self.buffer_startframe = 1
self.initialize()
self.buffer_around(1)
[docs]
def initialize(self, start_time=0):
"""Opens the file, creates the pipe."""
self.close() # if any
if start_time != 0:
offset = min(1, start_time)
i_arg = [
"-ss",
"%.05f" % (start_time - offset),
"-i",
ffmpeg_escape_filename(self.filename),
"-vn",
"-ss",
"%.05f" % offset,
]
else:
i_arg = ["-i", ffmpeg_escape_filename(self.filename), "-vn"]
cmd = (
[FFMPEG_BINARY]
+ i_arg
+ [
"-loglevel",
"error",
"-f",
self.format,
"-acodec",
self.codec,
"-ar",
"%d" % self.fps,
"-ac",
"%d" % self.nchannels,
"-",
]
)
popen_params = cross_platform_popen_params(
{
"bufsize": self.buffersize,
"stdout": sp.PIPE,
"stderr": sp.PIPE,
"stdin": sp.DEVNULL,
}
)
self.proc = sp.Popen(cmd, **popen_params)
self.pos = np.round(self.fps * start_time)
[docs]
def skip_chunk(self, chunksize):
"""Skip a chunk of audio data by reading and discarding the specified number of
frames from the audio stream. The audio stream is read from the `proc` stdout.
After skipping the chunk, the `pos` attribute is updated accordingly.
Parameters
----------
chunksize (int):
The number of audio frames to skip.
"""
_ = self.proc.stdout.read(self.nchannels * chunksize * self.nbytes)
self.proc.stdout.flush()
self.pos = self.pos + chunksize
[docs]
def read_chunk(self, chunksize):
"""Read a chunk of audio data from the audio stream.
This method reads a chunk of audio data from the audio stream. The
specified number of frames, given by `chunksize`, is read from the
`proc` stdout. The audio data is returned as a NumPy array, where
each row corresponds to a frame and each column corresponds to a
channel. If there is not enough audio left to read, the remaining
portion is padded with zeros, ensuring that the returned array has
the desired length. The `pos` attribute is updated accordingly.
Parameters
----------
chunksize (float):
The desired number of audio frames to read.
"""
# chunksize is not being autoconverted from float to int
chunksize = int(round(chunksize))
s = self.proc.stdout.read(self.nchannels * chunksize * self.nbytes)
data_type = {1: "int8", 2: "int16", 4: "int32"}[self.nbytes]
if hasattr(np, "frombuffer"):
result = np.frombuffer(s, dtype=data_type)
else:
result = np.fromstring(s, dtype=data_type)
result = (1.0 * result / 2 ** (8 * self.nbytes - 1)).reshape(
(int(len(result) / self.nchannels), self.nchannels)
)
# Pad the read chunk with zeros when there isn't enough audio
# left to read, so the buffer is always at full length.
pad = np.zeros((chunksize - len(result), self.nchannels), dtype=result.dtype)
result = np.concatenate([result, pad])
# self.proc.stdout.flush()
self.pos = self.pos + chunksize
return result
[docs]
def seek(self, pos):
"""Read a frame at time t. Note for coders: getting an arbitrary
frame in the video with ffmpeg can be painfully slow if some
decoding has to be done. This function tries to avoid fectching
arbitrary frames whenever possible, by moving between adjacent
frames.
"""
if (pos < self.pos) or (pos > (self.pos + 1000000)):
t = 1.0 * pos / self.fps
self.initialize(t)
elif pos > self.pos:
self.skip_chunk(pos - self.pos)
# last case standing: pos = current pos
self.pos = pos
[docs]
def get_frame(self, tt):
"""Retrieve the audio frame(s) corresponding to the given timestamp(s).
Parameters
----------
tt (float or numpy.ndarray):
The timestamp(s) at which to retrieve the audio frame(s).
If `tt` is a single float value, the frame corresponding to that
timestamp is returned. If `tt` is a NumPy array of timestamps, an
array of frames corresponding to each timestamp is returned.
"""
if isinstance(tt, np.ndarray):
# lazy implementation, but should not cause problems in
# 99.99 % of the cases
# elements of t that are actually in the range of the
# audio file.
in_time = (tt >= 0) & (tt < self.duration)
# Check that the requested time is in the valid range
if not in_time.any():
raise IOError(
"Error in file %s, " % (self.filename)
+ "Accessing time t=%.02f-%.02f seconds, " % (tt[0], tt[-1])
+ "with clip duration=%f seconds, " % self.duration
)
# The np.round in the next line is super-important.
# Removing it results in artifacts in the noise.
frames = np.round((self.fps * tt)).astype(int)[in_time]
fr_min, fr_max = frames.min(), frames.max()
# if min and max frames don't fit the buffer, it results in IndexError
# we avoid that by recursively calling this function on smaller length
# and concatenate the results:w
max_frame_threshold = fr_min + self.buffersize // 2
threshold_idx = np.searchsorted(frames, max_frame_threshold, side="right")
if threshold_idx != len(frames):
in_time_head = in_time[0:threshold_idx]
in_time_tail = in_time[threshold_idx:]
return np.concatenate(
[self.get_frame(in_time_head), self.get_frame(in_time_tail)]
)
if not (0 <= (fr_min - self.buffer_startframe) < len(self.buffer)):
self.buffer_around(fr_min)
elif not (0 <= (fr_max - self.buffer_startframe) < len(self.buffer)):
self.buffer_around(fr_max)
try:
result = np.zeros((len(tt), self.nchannels))
indices = frames - self.buffer_startframe
result[in_time] = self.buffer[indices]
return result
except IndexError as error:
warnings.warn(
"Error in file %s, " % (self.filename)
+ "At time t=%.02f-%.02f seconds, " % (tt[0], tt[-1])
+ "indices wanted: %d-%d, " % (indices.min(), indices.max())
+ "but len(buffer)=%d\n" % (len(self.buffer))
+ str(error),
UserWarning,
)
# repeat the last frame instead
indices[indices >= len(self.buffer)] = len(self.buffer) - 1
result[in_time] = self.buffer[indices]
return result
else:
ind = int(self.fps * tt)
if ind < 0 or ind > self.n_frames: # out of time: return 0
return np.zeros(self.nchannels)
if not (0 <= (ind - self.buffer_startframe) < len(self.buffer)):
# out of the buffer: recenter the buffer
self.buffer_around(ind)
# read the frame in the buffer
return self.buffer[ind - self.buffer_startframe]
[docs]
def buffer_around(self, frame_number):
"""Fill the buffer with frames, centered on frame_number if possible."""
# start-frame for the buffer
new_bufferstart = max(0, frame_number - self.buffersize // 2)
if self.buffer is not None:
current_f_end = self.buffer_startframe + self.buffersize
if new_bufferstart < current_f_end < new_bufferstart + self.buffersize:
# We already have part of what must be read
conserved = current_f_end - new_bufferstart
chunksize = self.buffersize - conserved
array = self.read_chunk(chunksize)
self.buffer = np.vstack([self.buffer[-conserved:], array])
else:
self.seek(new_bufferstart)
self.buffer = self.read_chunk(self.buffersize)
else:
self.seek(new_bufferstart)
self.buffer = self.read_chunk(self.buffersize)
self.buffer_startframe = new_bufferstart
[docs]
def close(self):
"""Closes the reader, terminating the subprocess if is still alive."""
if self.proc:
if self.proc.poll() is None:
self.proc.terminate()
self.proc.stdout.close()
self.proc.stderr.close()
self.proc.wait()
self.proc = None
def __del__(self):
# If the garbage collector comes, make sure the subprocess is terminated.
self.close()
