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Class that provides an ImageIO-like interface to a sequence of videos treated as a single video.
#!/usr/bin/env python3
"""
Class that provides an ImageIO-like interface to a sequence of videos treated as a single video.
"""
import bisect
import copy
import itertools
import imageio
def find_lub_cumsum_index(a, x):
"""
Find index of least upper bound of `x` in cumulative sum of list `a`.
"""
a_cumsum = list(itertools.accumulate(a))
i = bisect.bisect_right(a_cumsum, x)
if i != len(a):
return i
raise ValueError
class MultiVideoReader(object):
def __init__(self, *file_name_list):
self._readers = [imageio.get_reader(f) for f in file_name_list]
# Sanity checks to limit support to lists of videos with same format,
# fps, source_size, and size:
if len(set([r.format for r in self._readers])) > 1:
raise RuntimeError('all input readers must have same format')
meta = [r.get_meta_data() for r in self._readers]
if len(set([m['plugin'] for m in meta])) > 1:
raise RuntimeError('all inputs must be read with same plugin')
if meta[0]['plugin'] != 'ffmpeg':
raise RuntimeError('only ffmpeg supported')
if len(set([m['ffmpeg_version'] for m in meta])) > 1:
raise RuntimeError('all inputs must have same size')
if len(set([m['fps'] for m in meta])) > 1:
raise RuntimeError('all inputs must have same fps')
if len(set([m['source_size'] for m in meta])) > 1:
raise RuntimeError('all inputs must have same source size')
if len(set([m['size'] for m in meta])) > 1:
raise RuntimeError('all inputs must have same size')
# Set number of frames and duration respectively to sums of frames and
# durations of specified videos:
self._format = self._readers[0].format
self._nframes = [m['nframes'] for m in meta]
self._nframes_cumsum = list(itertools.accumulate(self._nframes))
self._duration = [m['duration'] for m in meta]
self._meta = copy.copy(meta[0])
self._meta['nframes'] = sum(self._nframes)
self._meta['duration'] = sum(self._duration)
@property
def format(self):
return self._format
def get_length(self):
return self._meta['nframes']
def get_meta_data(self):
return self._meta
def get_data(self, index):
i = find_lub_cumsum_index(self._nframes, index)
if i == 0:
return self._readers[i].get_data(index)
else:
return self._readers[i].get_data(index-self._nframes_cumsum[i-1])
def iter_data(self):
raise NotImplementedError
def __iter__(self):
return self.iter_data()
def get_reader(*file_name_list):
return MultiVideoFormat(file_name_list)
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