Gate opening with Raspberry Pi, motion and OpenALPR

Question

My project is Automatic License Plate Recognition (OpenALPR) to open a gate. I've a Raspberry Pi 2 with integrated cam. So far I managed to install Raspian, raspistill and raspivid are working. ALPR works in standalone mode, is able to detect license plates.

I installed motion and got mixed results, mainly because, I'm unsure about the procedure to select:

- should I concentrate on jpg (one/several files ?) which implies some not-so-obvious after-event programming - or is it more practical to get a right avi ? A single avi is of course much easier, just feed it to ALPR. There are many parameters and after much trial & error I've to beg for help.

I would appreciate some feedback or hints in my context, i.e. a car approching the gate, that is a motion of 20-30sec, generating a jpg every 10sec and a avi covering the whole 30sec.

  # /etc/motion/motion.conf
  # Daemon #########################################
  daemon on
  process_id_file /var/run/motion/motion.pid 
  # Basic Setup Mode ###############################
  setup_mode off
  # Capture device options #########################
  videodevice /dev/video0
  # v4l2_palette allows to choose preferable palette to be use by motion to 
  capture from those supported by your videodevice. (default: 8)
  # E.g. if your videodevice supports both V4L2_PIX_FMT_SBGGR8 and  
  V4L2_PIX_FMT_MJPEG 
  # then motion will by default use V4L2_PIX_FMT_MJPEG.
  # Setting v4l2_palette to 1 forces motion to use V4L2_PIX_FMT_SBGGR8 instead.
  #
  # Values :
  # V4L2_PIX_FMT_SN9C10X : 0  'S910'
  # V4L2_PIX_FMT_SBGGR8  : 1  'BA81'
  # V4L2_PIX_FMT_MJPEG   : 2  'MJPEG'
  # V4L2_PIX_FMT_JPEG    : 3  'JPEG'
  # V4L2_PIX_FMT_RGB24   : 4  'RGB3'
  # V4L2_PIX_FMT_UYVY    : 5  'UYVY'
  # V4L2_PIX_FMT_YUYV    : 6  'YUYV'
  # V4L2_PIX_FMT_YUV422P : 7  '422P'
  # V4L2_PIX_FMT_YUV420  : 8  'YU12'
  v4l2_palette 8
  ; tunerdevice /dev/tuner0
  input 8
  norm 0
  frequency 0
  rotate 180
  width 1024
  height 768
  framerate 5
  minimum_frame_time 0
  ; netcam_url value
  ; netcam_userpass value
  ; netcam_http 1.0
  ; netcam_proxy value 
  netcam_tolerant_check off
  auto_brightness off
  brightness 0
  contrast 0
  saturation 0
  hue 0
  # Round Robin (multiple inputs on same video device name) #########
  roundrobin_frames 1
  roundrobin_skip 1
  switchfilter off

  # Motion Detection Settings ##################################
  threshold 20000
  threshold_tune off
  noise_level 32
  noise_tune on
  # Despeckle motion image using (e)rode or (d)ilate or (l)abel (Default: not 
  defined)
  # Recommended value is EedDl. Any combination (and number of) of E, e, d, 
  and D is valid.
  # (l)abeling must only be used once and the 'l' must be the last letter.
  despeckle EedDl
  area_detect 258
  ; mask_file value
  smart_mask_speed 0
  lightswitch 0
  minimum_motion_frames 5
  pre_capture 0
  post_capture 0
  gap 10
  max_mpeg_time 30
  output_all off
  # Image File Output ##################################################
  output_normal best
  output_motion off
  quality 85
  ppm off
  # FFMPEG related options #########################################
  ffmpeg_cap_new on
  ffmpeg_cap_motion off
  ffmpeg_timelapse 0
  ffmpeg_timelapse_mode daily
  ffmpeg_bps 500000
  ffmpeg_variable_bitrate 0
  ffmpeg_video_codec mpeg4
  ffmpeg_deinterlace off
  # Snapshots (Traditional Periodic Webcam File Output) ################
  snapshot_interval 0
  # Text Display ######################
  # %Y = year, %m = month, %d = date,
  # %H = hour, %M = minute, %S = second, %T = HH:MM:SS,
  # %v = event, 
  # %q = frame number, 
  # %t = thread (camera) number,
  # %D = changed pixels, 
  # %N = noise level, 
  # \n = new line,
  # %i and %J = width and height of motion area,
  # %K and %L = X and Y coordinates of motion center
  # %C = value defined by text_event - do not use with text_event!
  locate off
  # text_right %Y-%m-%d\n%T-%q
  # text_left CAMERA %t
  text_changes off
  # This option defines the value of the special event conversion specifier %C
  # You can use any conversion specifier in this option except %C. 
  # Date and time  values are from the timestamp of the first image in the 
  current event.
  # Default: %Y%m%d%H%M%S
  # The idea is that %C can be used filenames and text_left/right for 
  creating  a unique identifier for each event.
  text_event %Y%m%d%H%M%S
  text_double off
  ############################################################
  # Target Directories and filenames for Images And Films
  # For the options snapshot_, jpeg_, mpeg_ and timelapse_filename
  # you can use conversion specifiers
  # %Y = year, %m = month, %d = date,
  # %H = hour, %M = minute, %S = second,
  # %v = event, %q = frame number, %t = thread (camera) number,
  # %D = changed pixels, %N = noise level,
  # %i and %J = width and height of motion area,
  # %K and %L = X and Y coordinates of motion center
  # %C = value defined by text_event
  # Quotation marks round string are allowed.
  ############################################################
  target_dir /data/webcam/motion
  # File path for snapshots (jpeg or ppm) relative to target_dir
  # Default: %v-%Y%m%d%H%M%S-snapshot
  # Default value is equivalent to legacy oldlayout option
  # For Motion 3.0 compatible mode choose: %Y/%m/%d/%H/%M/%S-snapshot
  # File extension .jpg or .ppm is automatically added so do not include this.
  # Note: A symbolic link called lastsnap.jpg created in the target_dir will 
  always
  # point to the latest snapshot, unless snapshot_filename is exactly 
  'lastsnap'
  # snapshot_filename %v-%Y%m%d%H%M%S-snapshot
  snapshot_filename pic-snap
  # File path for motion triggered images (jpeg or ppm) relative to target_dir
  # Default: %v-%Y%m%d%H%M%S-%q
  # Default value is equivalent to legacy oldlayout option
  # For Motion 3.0 compatible mode choose: %Y/%m/%d/%H/%M/%S-%q
  # File extension .jpg or .ppm is automatically added so do not include this
  # Set to 'preview' together with best-preview feature enables special naming
  # convention for preview shots.
  # See motion guide for details
  # jpeg_filename %v-%Y%m%d%H%M%S-%q
  jpeg_filename pic-motion
  # File path for motion triggered ffmpeg films (mpeg) relative to target_dir
  # Default: %v-%Y%m%d%H%M%S
  # Default value is equivalent to legacy oldlayout option
  # For Motion 3.0 compatible mode choose: %Y/%m/%d/%H%M%S
  # File extension .mpg or .avi is automatically added so do not include this
  # This option was previously called ffmpeg_filename
  # movie_filename %v-%Y%m%d%H%M%S
  movie_filename pic-movie
  # File path for timelapse mpegs relative to target_dir
  # Default: %Y%m%d-timelapse
  # Default value is near equivalent to legacy oldlayout option
  # For Motion 3.0 compatible mode choose: %Y/%m/%d-timelapse
  # File extension .mpg is automatically added so do not include this
  timelapse_filename %Y%m%d-timelapse
  # Live Webcam Server ###############################
  webcam_port 8080
  webcam_quality 85
  webcam_motion off
  webcam_maxrate 1
  webcam_localhost off
  webcam_limit 0

  # HTTP Based Control ##############################
  control_port 8081
  control_localhost on
  control_html_output on
  ; control_authentication username:password

  # Tracking (Pan/Tilt) ###########################
  # External Commands, Warnings and Logging:
  # You can use conversion specifiers for the on_xxxx commands
  # %Y = year, %m = month, %d = date,
  # %H = hour, %M = minute, %S = second,
  # %v = event, %q = frame number, %t = thread (camera) number,
  # %D = changed pixels, %N = noise level,
  # %i and %J = width and height of motion area,
  # %K and %L = X and Y coordinates of motion center
  # %C = value defined by text_event
  # %f = filename with full path
  # %n = number indicating filetype
  # Both %f and %n are only defined for on_picture_save,  on_movie_start and 
  on_movie_end
  ############################################################
  quiet on
  on_event_start /home/pi/.motion/echostart
  on_event_end /home/pi/.motion/echoend
  ; on_picture_save value
  ; on_motion_detected value
  ; on_area_detected value
  ; on_movie_start value
  ; on_movie_end value
  ; on_camera_lost value
  ############################################################
  # Common Options For MySQL and PostgreSQL database features.
  # Database Options For MySQL
  # Database Options For PostgreSQL
  # Video Loopback Device (vloopback project)
  ############################################################
  ; video_pipe value
  ; motion_video_pipe value
  ##############################################################
  # Thread config files - One for each camera.
  ##############################################################
  # thread config files. 
  ; thread /usr/local/etc/thread1.conf
  ; thread /usr/local/etc/thread2.conf
  ; thread /usr/local/etc/thread3.conf
  ; thread /usr/local/etc/thread4.conf

Environment

Motion version:	3.2.12
ffmpeg version:	N-77432-gc0f67e1
Libraries:	ffmpeg
Server OS:	Raspbian GNU/Linux 7 \n \l

-- RaymondWarichet - 05 Jan 2016

Answer