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# -*- coding: utf-8 -*-
# Copyright (c) 2013 Adrian Taylor
# Inspired by equivalent node.js code by Felix Geisendörfer
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import struct
"""
The AR Drone 2.0 allows a tcp client to receive H264 (MPEG4.10 AVC) video
from the drone. However, the frames are wrapped by Parrot Video
Encapsulation (PaVE), which this class parses.
"""
"""
Usage: Pass in an output file object into the constructor, then call write on this.
"""
class PaVEParser(object):
HEADER_SIZE_SHORT = 64; # sometimes header is longer
def __init__(self, outfileobject):
self.buffer = ""
self.state = self.handle_header
self.outfileobject = outfileobject
self.misaligned_frames = 0
self.payloads = 0
self.drop_old_frames = True
self.align_on_iframe = True
if self.drop_old_frames:
self.state = self.handle_header_drop_frames
def write(self, data):
self.buffer += data
while True:
made_progress = self.state()
if not made_progress:
return
def handle_header(self):
if self.fewer_remaining_than(self.HEADER_SIZE_SHORT):
return False
(signature, version, video_codec, header_size, self.payload_size, encoded_stream_width,
encoded_stream_height, display_width, display_height, frame_number, timestamp, total_chunks,
chunk_index, frame_type, control, stream_byte_position_lw, stream_byte_position_uw,
stream_id, total_slices, slice_index, header1_size, header2_size,
reserved2, advertised_size, reserved3) = struct.unpack("<4sBBHIHHHHIIBBBBIIHBBBB2sI12s",
self.buffer[0:self.HEADER_SIZE_SHORT])
if signature != "PaVE":
self.state = self.handle_misalignment
return True
self.buffer = self.buffer[header_size:]
self.state = self.handle_payload
return True
def handle_header_drop_frames(self):
eligible_index = self.buffer.find('PaVE')
if (eligible_index < 0):
return False
self.buffer = self.buffer[eligible_index:]
if self.fewer_remaining_than(self.HEADER_SIZE_SHORT):
return False
eligible_index = 0
current_index = eligible_index
while current_index != -1 and len(self.buffer[current_index:]) > self.HEADER_SIZE_SHORT:
(signature, version, video_codec, header_size, payload_size, encoded_stream_width,
encoded_stream_height, display_width, display_height, frame_number, timestamp, total_chunks,
chunk_index, frame_type, control, stream_byte_position_lw, stream_byte_position_uw,
stream_id, total_slices, slice_index, header1_size,
header2_size, reserved2, advertised_size,
reserved3) = struct.unpack("<4sBBHIHHHHIIBBBBIIHBBBB2sI12s",
self.buffer[current_index:current_index + self.HEADER_SIZE_SHORT])
if (frame_type != 3 or current_index == 0):
eligible_index = current_index
self.payload_size = payload_size
offset = self.buffer[current_index + 1:].find('PaVE') + 1
if (offset == 0):
break
current_index += offset
self.buffer = self.buffer[eligible_index + header_size:]
self.state = self.handle_payload
return True
def handle_misalignment(self):
"""Sometimes we start of in the middle of frame - look for the PaVE header."""
IFrame = False
if self.align_on_iframe:
while (not IFrame):
index = self.buffer.find('PaVE')
if index == -1:
return False
self.buffer = self.buffer[index:]
if self.fewer_remaining_than(self.HEADER_SIZE_SHORT):
return False
(signature, version, video_codec, header_size, self.payload_size, encoded_stream_width,
encoded_stream_height, display_width, display_height, frame_number, timestamp, total_chunks,
chunk_index, frame_type, control, stream_byte_position_lw, stream_byte_position_uw,
stream_id, total_slices, slice_index, header1_size, header2_size, reserved2, advertised_size,
reserved3) = struct.unpack("<4sBBHIHHHHIIBBBBIIHBBBB2sI12s", self.buffer[0:self.HEADER_SIZE_SHORT])
IFrame = (frame_type == 1 or frame_type == 2)
if not IFrame:
self.buffer = self.buffer[header_size:]
else:
index = self.buffer.find('PaVE')
if index == -1:
return False
self.buffer = self.buffer[index:]
self.misaligned_frames += 1
self.state = self.handle_header
return True
def handle_payload(self):
if self.fewer_remaining_than(self.payload_size):
return False
self.state = self.handle_header
if self.drop_old_frames:
self.state = self.handle_header_drop_frames
self.outfileobject.write(self.buffer[0:self.payload_size])
self.buffer = self.buffer[self.payload_size:]
self.payloads += 1
return True
def fewer_remaining_than(self, desired_size):
return len(self.buffer) < desired_size
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