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import os.path as osp |
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from collections import OrderedDict |
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import cv2 |
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from cv2 import (CAP_PROP_FOURCC, CAP_PROP_FPS, CAP_PROP_FRAME_COUNT, |
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CAP_PROP_FRAME_HEIGHT, CAP_PROP_FRAME_WIDTH, |
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CAP_PROP_POS_FRAMES, VideoWriter_fourcc) |
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from annotator.mmpkg.mmcv.utils import (check_file_exist, mkdir_or_exist, scandir, |
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track_progress) |
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class Cache: |
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def __init__(self, capacity): |
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self._cache = OrderedDict() |
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self._capacity = int(capacity) |
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if capacity <= 0: |
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raise ValueError('capacity must be a positive integer') |
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@property |
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def capacity(self): |
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return self._capacity |
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@property |
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def size(self): |
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return len(self._cache) |
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def put(self, key, val): |
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if key in self._cache: |
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return |
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if len(self._cache) >= self.capacity: |
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self._cache.popitem(last=False) |
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self._cache[key] = val |
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def get(self, key, default=None): |
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val = self._cache[key] if key in self._cache else default |
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return val |
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class VideoReader: |
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"""Video class with similar usage to a list object. |
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This video warpper class provides convenient apis to access frames. |
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There exists an issue of OpenCV's VideoCapture class that jumping to a |
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certain frame may be inaccurate. It is fixed in this class by checking |
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the position after jumping each time. |
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Cache is used when decoding videos. So if the same frame is visited for |
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the second time, there is no need to decode again if it is stored in the |
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cache. |
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:Example: |
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>>> import annotator.mmpkg.mmcv as mmcv |
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>>> v = mmcv.VideoReader('sample.mp4') |
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>>> len(v) # get the total frame number with `len()` |
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120 |
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>>> for img in v: # v is iterable |
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>>> mmcv.imshow(img) |
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>>> v[5] # get the 6th frame |
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""" |
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def __init__(self, filename, cache_capacity=10): |
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if not filename.startswith(('https://', 'http://')): |
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check_file_exist(filename, 'Video file not found: ' + filename) |
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self._vcap = cv2.VideoCapture(filename) |
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assert cache_capacity > 0 |
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self._cache = Cache(cache_capacity) |
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self._position = 0 |
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self._width = int(self._vcap.get(CAP_PROP_FRAME_WIDTH)) |
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self._height = int(self._vcap.get(CAP_PROP_FRAME_HEIGHT)) |
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self._fps = self._vcap.get(CAP_PROP_FPS) |
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self._frame_cnt = int(self._vcap.get(CAP_PROP_FRAME_COUNT)) |
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self._fourcc = self._vcap.get(CAP_PROP_FOURCC) |
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@property |
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def vcap(self): |
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""":obj:`cv2.VideoCapture`: The raw VideoCapture object.""" |
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return self._vcap |
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@property |
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def opened(self): |
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"""bool: Indicate whether the video is opened.""" |
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return self._vcap.isOpened() |
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@property |
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def width(self): |
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"""int: Width of video frames.""" |
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return self._width |
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@property |
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def height(self): |
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"""int: Height of video frames.""" |
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return self._height |
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@property |
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def resolution(self): |
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"""tuple: Video resolution (width, height).""" |
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return (self._width, self._height) |
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@property |
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def fps(self): |
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"""float: FPS of the video.""" |
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return self._fps |
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@property |
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def frame_cnt(self): |
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"""int: Total frames of the video.""" |
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return self._frame_cnt |
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@property |
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def fourcc(self): |
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"""str: "Four character code" of the video.""" |
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return self._fourcc |
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@property |
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def position(self): |
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"""int: Current cursor position, indicating frame decoded.""" |
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return self._position |
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def _get_real_position(self): |
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return int(round(self._vcap.get(CAP_PROP_POS_FRAMES))) |
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def _set_real_position(self, frame_id): |
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self._vcap.set(CAP_PROP_POS_FRAMES, frame_id) |
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pos = self._get_real_position() |
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for _ in range(frame_id - pos): |
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self._vcap.read() |
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self._position = frame_id |
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def read(self): |
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"""Read the next frame. |
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If the next frame have been decoded before and in the cache, then |
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return it directly, otherwise decode, cache and return it. |
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Returns: |
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ndarray or None: Return the frame if successful, otherwise None. |
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""" |
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if self._cache: |
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img = self._cache.get(self._position) |
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if img is not None: |
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ret = True |
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else: |
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if self._position != self._get_real_position(): |
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self._set_real_position(self._position) |
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ret, img = self._vcap.read() |
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if ret: |
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self._cache.put(self._position, img) |
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else: |
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ret, img = self._vcap.read() |
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if ret: |
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self._position += 1 |
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return img |
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def get_frame(self, frame_id): |
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"""Get frame by index. |
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Args: |
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frame_id (int): Index of the expected frame, 0-based. |
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Returns: |
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ndarray or None: Return the frame if successful, otherwise None. |
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""" |
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if frame_id < 0 or frame_id >= self._frame_cnt: |
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raise IndexError( |
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f'"frame_id" must be between 0 and {self._frame_cnt - 1}') |
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if frame_id == self._position: |
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return self.read() |
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if self._cache: |
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img = self._cache.get(frame_id) |
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if img is not None: |
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self._position = frame_id + 1 |
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return img |
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self._set_real_position(frame_id) |
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ret, img = self._vcap.read() |
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if ret: |
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if self._cache: |
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self._cache.put(self._position, img) |
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self._position += 1 |
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return img |
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def current_frame(self): |
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"""Get the current frame (frame that is just visited). |
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Returns: |
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ndarray or None: If the video is fresh, return None, otherwise |
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return the frame. |
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""" |
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if self._position == 0: |
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return None |
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return self._cache.get(self._position - 1) |
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def cvt2frames(self, |
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frame_dir, |
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file_start=0, |
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filename_tmpl='{:06d}.jpg', |
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start=0, |
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max_num=0, |
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show_progress=True): |
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"""Convert a video to frame images. |
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Args: |
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frame_dir (str): Output directory to store all the frame images. |
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file_start (int): Filenames will start from the specified number. |
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filename_tmpl (str): Filename template with the index as the |
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placeholder. |
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start (int): The starting frame index. |
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max_num (int): Maximum number of frames to be written. |
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show_progress (bool): Whether to show a progress bar. |
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""" |
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mkdir_or_exist(frame_dir) |
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if max_num == 0: |
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task_num = self.frame_cnt - start |
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else: |
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task_num = min(self.frame_cnt - start, max_num) |
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if task_num <= 0: |
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raise ValueError('start must be less than total frame number') |
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if start > 0: |
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self._set_real_position(start) |
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def write_frame(file_idx): |
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img = self.read() |
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if img is None: |
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return |
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filename = osp.join(frame_dir, filename_tmpl.format(file_idx)) |
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cv2.imwrite(filename, img) |
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if show_progress: |
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track_progress(write_frame, range(file_start, |
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file_start + task_num)) |
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else: |
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for i in range(task_num): |
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write_frame(file_start + i) |
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def __len__(self): |
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return self.frame_cnt |
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def __getitem__(self, index): |
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if isinstance(index, slice): |
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return [ |
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self.get_frame(i) |
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for i in range(*index.indices(self.frame_cnt)) |
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] |
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if index < 0: |
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index += self.frame_cnt |
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if index < 0: |
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raise IndexError('index out of range') |
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return self.get_frame(index) |
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def __iter__(self): |
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self._set_real_position(0) |
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return self |
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def __next__(self): |
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img = self.read() |
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if img is not None: |
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return img |
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else: |
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raise StopIteration |
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next = __next__ |
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def __enter__(self): |
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return self |
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def __exit__(self, exc_type, exc_value, traceback): |
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self._vcap.release() |
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def frames2video(frame_dir, |
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video_file, |
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fps=30, |
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fourcc='XVID', |
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filename_tmpl='{:06d}.jpg', |
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start=0, |
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end=0, |
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show_progress=True): |
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"""Read the frame images from a directory and join them as a video. |
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Args: |
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frame_dir (str): The directory containing video frames. |
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video_file (str): Output filename. |
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fps (float): FPS of the output video. |
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fourcc (str): Fourcc of the output video, this should be compatible |
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with the output file type. |
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filename_tmpl (str): Filename template with the index as the variable. |
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start (int): Starting frame index. |
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end (int): Ending frame index. |
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show_progress (bool): Whether to show a progress bar. |
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""" |
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if end == 0: |
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ext = filename_tmpl.split('.')[-1] |
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end = len([name for name in scandir(frame_dir, ext)]) |
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first_file = osp.join(frame_dir, filename_tmpl.format(start)) |
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check_file_exist(first_file, 'The start frame not found: ' + first_file) |
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img = cv2.imread(first_file) |
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height, width = img.shape[:2] |
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resolution = (width, height) |
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vwriter = cv2.VideoWriter(video_file, VideoWriter_fourcc(*fourcc), fps, |
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resolution) |
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def write_frame(file_idx): |
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filename = osp.join(frame_dir, filename_tmpl.format(file_idx)) |
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img = cv2.imread(filename) |
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vwriter.write(img) |
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if show_progress: |
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track_progress(write_frame, range(start, end)) |
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else: |
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for i in range(start, end): |
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write_frame(i) |
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vwriter.release() |
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