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from pathlib import Path
import gpmf
import numpy as np
from gyraudio.properties import GYRO_KEY, ACCL_KEY
def extract_imu_blocks(stream, key=GYRO_KEY):
""" Extract imu data blocks from binary stream
This is a generator on lists `KVLItem` objects. In
the GPMF stream, imu data comes into blocks of several
different data items. For each of these blocks we return a list.
Parameters
----------
stream: bytes
The raw GPMF binary stream
Returns
-------
imu_items_generator: generator
Generator of lists of `KVLItem` objects
"""
for s in gpmf.parse.filter_klv(stream, "STRM"):
content = []
is_imu = False
for elt in s.value:
content.append(elt)
if elt.key == key:
is_imu = True
if is_imu:
yield content
def parse_imu_block(imu_block, key=GYRO_KEY):
"""Turn imu data blocks into `imuData` objects
Parameters
----------
imu_block: list of KVLItem
A list of KVLItem corresponding to a imu data block.
Returns
-------
imu_data: imuData
A imuData object holding the imu information of a block.
"""
block_dict = {
s.key: s for s in imu_block
}
imu_data = block_dict[key].value * 1.0 / block_dict["SCAL"].value
return {
"timestamp": block_dict["TSMP"],
key: imu_data,
}
def get_imu_data(pth: Path) -> np.array:
"""Extract imu data from GPMF metadata from a Gopro video file
Parameters
----------
path: str
Path to the GPMF file
Returns
-------
imu_data: list of imuData
List of imuData objects holding the imu information of the file.
"""
stream = gpmf.io.extract_gpmf_stream(pth)
imu_data_dict = {}
for key in [GYRO_KEY, ACCL_KEY]:
imu_blocks = extract_imu_blocks(stream, key=key)
imu_data = [parse_imu_block(imu_block, key=key) for imu_block in imu_blocks]
imu_data_dict[key] = np.vstack([np.array(imu[key]) for imu in imu_data])
return imu_data_dict[GYRO_KEY], imu_data_dict[ACCL_KEY]
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