How to parse Apollo Record files?
======================

How to parse Apollo Record files (e.g., extract point cloud, image messages)?

-  Maintainer: \ daohu527@gmail.com, yhuai@uci.edu
-  Version：1.0.0
-  Date：06/05/2024
-  Description：This document introduces how to extract data from Apollo Record files.

Answer
----

`cyber_recorder <https://cyber-rt.readthedocs.io/en/latest/CyberRT_Developer_Tools.html>`_ \ can be used to record messages published by each module of Apollo at run time,
saves those messages in record file(s), and users can extract data from the record file(s)
for model training, problem analysis, etc.

How to extract data from the record file(s)?

Installation
~~~~

``cyber_record`` \ is a Python implementation of Apollo Record read/write tool,
it provides both command line and API interfaces. It is a light weight cross-platform tool,
with a disadvantage of slow speed.

.. code:: shell

   pip3 install cyber_record record_msg

Read Images
~~~~~~~~

Specify the name of the ``topic`` to read image from,
and the path ``output_path`` to save the image.
Then, run the following code.

.. code:: python

   from cyber_record.record import Record
   from record_msg.parser import ImageParser

   image_parser = ImageParser(output_path='../test')
   for topic, message, t in record.read_messages():
     if topic == "/apollo/sensor/camera/front_6mm/image":
       image_parser.parse(message)
       # or use timestamp as image file name
       # image_parser.parse(image, t)

Read Point Cloud
~~~~~~~~

Specify the name of the ``topic`` to read point cloud from,
and the path ``output_path`` to save the point cloud.
Then, run the following code.

.. code:: python

   from cyber_record.record import Record
   from record_msg.parser import PointCloudParser

   pointcloud_parser = PointCloudParser('../test')
   for topic, message, t in record.read_messages():
     if topic == "/apollo/sensor/lidar32/compensator/PointCloud2":
       pointcloud_parser.parse(message)
       # other modes, default is 'ascii'
       # pointcloud_parser.parse(message, mode='binary')
       # pointcloud_parser.parse(message, mode='binary_compressed')


Increasing Reading Speed
~~~~~~~~

For faster reading, you can use filter to read messages from a specific topic or within a specific time range.

.. code:: python

   def read_filter_by_both():
     record = Record(file_name)
     for topic, message, t in record.read_messages('/apollo/canbus/chassis', \
         start_time=1627031535164278940, end_time=1627031535215164773):
       print("{}, {}, {}".format(topic, type(message), t))