Source code for picamera.streams

# vim: set et sw=4 sts=4 fileencoding=utf-8:
#
# Python camera library for the Rasperry-Pi camera module
# Copyright (c) 2013-2015 Dave Jones <dave@waveform.org.uk>
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"""
The streams module defines stream classes suited to generating certain types of
camera output (beyond those provided by Python by default). Currently, this
consists primarily of :class:`~PiCameraCircularIO`.

.. note::

    All classes in this module are available from the :mod:`picamera` namespace
    without having to import :mod:`picamera.streams` directly.

The following classes are defined in the module:


PiCameraCircularIO
==================

.. autoclass:: PiCameraCircularIO
    :members:


CircularIO
==========

.. autoclass:: CircularIO
    :members:

"""

from __future__ import (
    unicode_literals,
    print_function,
    division,
    absolute_import,
    )

# Make Py2's str equivalent to Py3's
str = type('')


import io
from threading import RLock
from collections import deque

from picamera.exc import PiCameraValueError
from picamera.encoders import PiVideoFrame


__all__ = [
    'CircularIO',
    'PiCameraCircularIO',
    ]


[docs]class CircularIO(io.IOBase): """ A thread-safe stream which uses a ring buffer for storage. CircularIO provides an in-memory stream similar to the :class:`io.BytesIO` class. However, unlike BytesIO its underlying storage is a `ring buffer`_ with a fixed maximum size. Once the maximum size is reached, writing effectively loops round to the beginning to the ring and starts overwriting the oldest content. The *size* parameter specifies the maximum size of the stream in bytes. The :meth:`read`, :meth:`tell`, and :meth:`seek` methods all operate equivalently to those in :class:`io.BytesIO` whilst :meth:`write` only differs in the wrapping behaviour described above. A :meth:`read1` method is also provided for efficient reading of the underlying ring buffer in write-sized chunks (or less). A re-entrant threading lock guards all operations, and is accessible for external use via the :attr:`lock` attribute. The performance of the class is geared toward faster writing than reading on the assumption that writing will be the common operation and reading the rare operation (a reasonable assumption for the camera use-case, but not necessarily for more general usage). .. _ring buffer: http://en.wikipedia.org/wiki/Circular_buffer """ def __init__(self, size): if size < 1: raise ValueError('size must be a positive integer') self._lock = RLock() self._data = deque() self._size = size self._length = 0 self._pos = 0 self._pos_index = 0 self._pos_offset = 0 @property def lock(self): """ A re-entrant threading lock which is used to guard all operations. """ return self._lock @property def size(self): """ Return the maximum size of the buffer in bytes. """ return self._size
[docs] def readable(self): """ Returns ``True``, indicating that the stream supports :meth:`read`. """ return True
[docs] def writable(self): """ Returns ``True``, indicating that the stream supports :meth:`write`. """ return True
[docs] def seekable(self): """ Returns ``True``, indicating the stream supports :meth:`seek` and :meth:`tell`. """ return True
[docs] def getvalue(self): """ Return ``bytes`` containing the entire contents of the buffer. """ with self.lock: return b''.join(self._data)
def _set_pos(self, value): self._pos = value self._pos_index = -1 self._pos_offset = chunk_pos = 0 for self._pos_index, chunk in enumerate(self._data): if chunk_pos + len(chunk) > value: self._pos_offset = value - chunk_pos return else: chunk_pos += len(chunk) self._pos_index += 1 self._pos_offset = value - chunk_pos
[docs] def tell(self): """ Return the current stream position. """ return self._pos
[docs] def seek(self, offset, whence=io.SEEK_SET): """ Change the stream position to the given byte *offset*. *offset* is interpreted relative to the position indicated by *whence*. Values for *whence* are: * ``SEEK_SET`` or ``0`` – start of the stream (the default); *offset* should be zero or positive * ``SEEK_CUR`` or ``1`` – current stream position; *offset* may be negative * ``SEEK_END`` or ``2`` – end of the stream; *offset* is usually negative Return the new absolute position. """ with self.lock: if whence == io.SEEK_CUR: offset = self._pos + offset elif whence == io.SEEK_END: offset = self._length + offset if offset < 0: raise ValueError( 'New position is before the start of the stream') self._set_pos(offset) return self._pos
[docs] def read(self, n=-1): """ Read up to *n* bytes from the stream and return them. As a convenience, if *n* is unspecified or -1, :meth:`readall` is called. Fewer than *n* bytes may be returned if there are fewer than *n* bytes from the current stream position to the end of the stream. If 0 bytes are returned, and *n* was not 0, this indicates end of the stream. """ if n == -1: return self.readall() else: with self.lock: if self._pos == self._length: return b'' from_index, from_offset = self._pos_index, self._pos_offset self._set_pos(self._pos + n) result = self._data[from_index][from_offset:from_offset + n] # Bah ... can't slice a deque for i in range(from_index + 1, self._pos_index): result += self._data[i] if from_index < self._pos_index < len(self._data): result += self._data[self._pos_index][:self._pos_offset] return result
[docs] def readall(self): """ Read and return all bytes from the stream until EOF, using multiple calls to the stream if necessary. """ return self.read(self._length - self._pos)
[docs] def read1(self, n=-1): """ Read up to *n* bytes from the stream using only a single call to the underlying object. In the case of :class:`CircularIO` this roughly corresponds to returning the content from the current position up to the end of the write that added that content to the stream (assuming no subsequent writes overwrote the content). :meth:`read1` is particularly useful for efficient copying of the stream's content. """ with self.lock: if self._pos == self._length: return b'' chunk = self._data[self._pos_index] if n == -1: n = len(chunk) - self._pos_offset result = chunk[self._pos_offset:self._pos_offset + n] self._pos += len(result) self._pos_offset += n if self._pos_offset >= len(chunk): self._pos_index += 1 self._pos_offset = 0 return result
[docs] def truncate(self, size=None): """ Resize the stream to the given *size* in bytes (or the current position if *size* is not specified). This resizing can extend or reduce the current stream size. In case of extension, the contents of the new file area will be NUL (``\\x00``) bytes. The new stream size is returned. The current stream position isn’t changed unless the resizing is expanding the stream, in which case it may be set to the maximum stream size if the expansion causes the ring buffer to loop around. """ with self.lock: if size is None: size = self._pos if size < 0: raise ValueError('size must be zero, or a positive integer') if size > self._length: # Backfill the space between stream end and current position # with NUL bytes fill = b'\x00' * (size - self._length) self._set_pos(self._length) self.write(fill) elif size < self._length: # Lop off chunks until we get to the last one at the truncation # point, and slice that one save_pos = self._pos self._set_pos(size) while self._pos_index < len(self._data) - 1: self._data.pop() self._data[self._pos_index] = self._data[self._pos_index][:self._pos_offset] self._length = size self._pos_index += 1 self._pos_offset = 0 if self._pos != save_pos: self._set_pos(save_pos)
[docs] def write(self, b): """ Write the given bytes or bytearray object, *b*, to the underlying stream and return the number of bytes written. """ b = bytes(b) with self.lock: # Special case: stream position is beyond the end of the stream. # Call truncate to backfill space first if self._pos > self._length: self.truncate() result = len(b) if self._pos == self._length: # Fast path: stream position is at the end of the stream so # just append a new chunk self._data.append(b) self._length += len(b) self._pos = self._length self._pos_index = len(self._data) self._pos_offset = 0 else: # Slow path: stream position is somewhere in the middle; # overwrite bytes in the current (and if necessary, subsequent) # chunk(s), without extending them. If we reach the end of the # stream, call ourselves recursively to continue down the fast # path while b and (self._pos < self._length): chunk = self._data[self._pos_index] head = b[:len(chunk) - self._pos_offset] assert head b = b[len(head):] self._data[self._pos_index] = b''.join(( chunk[:self._pos_offset], head, chunk[self._pos_offset + len(head):] )) self._pos += len(head) if self._pos_offset + len(head) >= len(chunk): self._pos_index += 1 self._pos_offset = 0 else: self._pos_offset += len(head) if b: self.write(b) # If the stream is now beyond the specified size limit, remove # chunks (or part of a chunk) until the size is within the limit # again while self._length > self._size: chunk = self._data[0] if self._length - len(chunk) >= self._size: # Need to remove the entire chunk self._data.popleft() self._length -= len(chunk) self._pos -= len(chunk) self._pos_index -= 1 # no need to adjust self._pos_offset else: # need to remove the head of the chunk self._data[0] = chunk[self._length - self._size:] self._pos -= self._length - self._size self._length = self._size return result
class PiCameraDequeHack(deque): def __init__(self, camera, splitter_port=1): super(PiCameraDequeHack, self).__init__() self.camera = camera self.splitter_port = splitter_port def append(self, item): encoder = self.camera._encoders[self.splitter_port] if encoder.frame.complete: # If the chunk being appended is the end of a new frame, include # the frame's metadata from the camera return super(PiCameraDequeHack, self).append((item, encoder.frame)) else: return super(PiCameraDequeHack, self).append((item, None)) def pop(self): return super(PiCameraDequeHack, self).pop()[0] def popleft(self): return super(PiCameraDequeHack, self).popleft()[0] def __getitem__(self, index): return super(PiCameraDequeHack, self).__getitem__(index)[0] def __setitem__(self, index, value): frame = super(PiCameraDequeHack, self).__getitem__(index)[1] return super(PiCameraDequeHack, self).__setitem__(index, (value, frame)) def __iter__(self): for item, frame in super(PiCameraDequeHack, self).__iter__(): yield item class PiCameraDequeFrames(object): def __init__(self, stream): super(PiCameraDequeFrames, self).__init__() self.stream = stream def __iter__(self): with self.stream.lock: pos = 0 for item, frame in super(PiCameraDequeHack, self.stream._data).__iter__(): pos += len(item) if frame: # Rewrite the video_size and split_size attributes according # to the current position of the chunk frame = PiVideoFrame( index=frame.index, frame_type=frame.frame_type, frame_size=frame.frame_size, video_size=pos, split_size=pos, timestamp=frame.timestamp, complete=frame.complete, ) # Only yield the frame meta-data if the start of the frame # still exists in the stream if pos - frame.frame_size >= 0: yield frame def __reversed__(self): with self.stream.lock: pos = self.stream._length for item, frame in super(PiCameraDequeHack, self.stream._data).__reversed__(): if frame: frame = PiVideoFrame( index=frame.index, frame_type=frame.frame_type, frame_size=frame.frame_size, video_size=pos, split_size=pos, timestamp=frame.timestamp, complete=frame.complete, ) if pos - frame.frame_size >= 0: yield frame pos -= len(item)
[docs]class PiCameraCircularIO(CircularIO): """ A derivative of :class:`CircularIO` which tracks camera frames. PiCameraCircularIO provides an in-memory stream based on a ring buffer. It is a specialization of :class:`CircularIO` which associates video frame meta-data with the recorded stream, accessible from the :attr:`frames` property. .. warning:: The class makes a couple of assumptions which will cause the frame meta-data tracking to break if they are not adhered to: * the stream is only ever appended to - no writes ever start from the middle of the stream * the stream is never truncated (from the right; being ring buffer based, left truncation will occur automatically) The *camera* parameter specifies the :class:`~picamera.camera.PiCamera` instance that will be recording video to the stream. If specified, the *size* parameter determines the maximum size of the stream in bytes. If *size* is not specified (or ``None``), then *seconds* must be specified instead. This provides the maximum length of the stream in seconds, assuming a data rate in bits-per-second given by the *bitrate* parameter (which defaults to ``17000000``, or 17Mbps, which is also the default bitrate used for video recording by :class:`~picamera.camera.PiCamera`). You cannot specify both *size* and *seconds*. The *splitter_port* parameter specifies the port of the built-in splitter that the video encoder will be attached to. This defaults to ``1`` and most users will have no need to specify anything different. If you do specify something else, ensure it is equal to the *splitter_port* parameter of the corresponding call to :meth:`~picamera.camera.PiCamera.start_recording`. For example:: import picamera with picamera.PiCamera() as camera: with picamera.PiCameraCircularIO(camera, splitter_port=2) as stream: camera.start_recording(stream, format='h264', splitter_port=2) camera.wait_recording(10, splitter_port=2) camera.stop_recording(splitter_port=2) .. attribute:: frames Returns an iterator over the frame meta-data. As the camera records video to the stream, the class captures the meta-data associated with each frame (in the form of a :class:`~picamera.encoders.PiVideoFrame` tuple), discarding meta-data for frames which are no longer fully stored within the underlying ring buffer. You can use the frame meta-data to locate, for example, the first keyframe present in the stream in order to determine an appropriate range to extract. """ def __init__( self, camera, size=None, seconds=None, bitrate=17000000, splitter_port=1): if size is None and seconds is None: raise PiCameraValueError('You must specify either size, or seconds') if size is not None and seconds is not None: raise PiCameraValueError('You cannot specify both size and seconds') if seconds is not None: size = bitrate * seconds // 8 super(PiCameraCircularIO, self).__init__(size) self._data = PiCameraDequeHack(camera, splitter_port) self.frames = PiCameraDequeFrames(self)