gpscam_5inch.py

""" Raspberry Pi + GPS Car Camera
Achieved with three threads:

1. Main thread - 
       Start preview and recording.

2. GPS thread - 
       Read GPS location.

3. Annotate thread - 
       Put GPS location and datetime on image.
       Refresh every one second to simulate a running clock.

Should be coupled with a cron job which deletes old video clips,
to prevent disk from filling up.

**Customize video size, preview dimension, and clip directory before trying.**
"""

import picamera
from datetime import datetime
import threading
import time
import os.path
import gps

video_size = (640, 480)
preview_dimension = (160, 0, 640, 480)  # x, y, w, h
clip_directory = Full path to your clip directory, e.g. /home/pi/gpscam/clips

def record(camera):
    def datetime_filename():
        while 1:
            yield (
                os.path.join(
                    clip_directory, 
                    datetime.now().strftime('%Y%m%d-%H%M') + '.h264'))

    def seconds_to_cutoff():
        cutoffs = [15, 30, 45, 60]
        now = datetime.now()
        for c in cutoffs:
            if c <= now.minute:
                continue
            return c*60 - now.minute*60 - now.second

    for filename in camera.record_sequence(datetime_filename()):
        camera.wait_recording(seconds_to_cutoff())

latest_location = None

def gpsread():
    global latest_location
    session = gps.gps(mode=gps.WATCH_ENABLE | gps.WATCH_NEWSTYLE)
    for report in session:
        if report['class'] == 'TPV':
            if report['mode'] in [2,3]:
                latest_location = (report['lat'], report['lon'])
            else:
                latest_location = None

# Separate annotation from GPS because I want to refresh the text
# once per second to give an illusion of a running clock.
def annotate(camera):
    def compose_text(dt, location):
        if location:
            lat, lon = location
            loctext = '%.4f%s %.4f%s' % (lat, 
                                         'N' if lat >= 0 else 'S', 
                                         lon, 
                                         'E' if lon >= 0 else 'W')
        else:
            loctext = '--lat-- --lon--'

        return dt.strftime('%Y-%m-%d %H:%M:%S ') + loctext

    global latest_location
    camera.annotate_text_size = 24
    while 1:
        camera.annotate_text = compose_text(datetime.now(), 
                                            latest_location)
        time.sleep(1)


camera = picamera.PiCamera(resolution=video_size, framerate=30)

gps_thread = threading.Thread(target=gpsread)
gps_thread.daemon = True
gps_thread.start()

annotate_thread = threading.Thread(target=annotate, args=[camera])
annotate_thread.daemon = True
annotate_thread.start()

camera.start_preview(fullscreen=False, window=preview_dimension)
record(camera)