Ok Monitor

• VGA or HDMI connection
• Resolution 1024x768 or lower
• 5 fps - 6 inch screen or
• 6 fps - 12 inch screens
• Wireless, around 2 hours+
• :( lag of around 1.2 seconds.

An okay eInk Monitor ?

TL; DR;

• HDMI USB Capture card
• PI encodes to kindle eink format
• PI Wireless Access Point
• Quad-Core PI Streams 1/4 per core
• Jailbreak Kindle(s) display

Hardware

• Kindle Paperwhite(s) (depreciating)
• Raspberry Pi4
• HDMI to USB Capture
• Plus

  • microSD Card
  • Cables
  • PI PSU

Software

• OpenWRT
• ffmpeg
• GeekMaster Video
• KUAL

Operation

Single Screen

Close Up

Kindle

• Paperwhite 1
• Around £37 Cex
• Runs linux
• Battery amazing

Jailbreak

• Paperwhite 1 (all firmware)
• Takes around 20 mins
• Documented on website
• No soldering!

KUAL

Kindle Unified Application Launcher

• Launcher application
• Highly Configurable

PI 4

• Faster processor
• Quad Core

USB HDMI Capture

• Cheap! £8-£12
• Adds some lag
• Can use a VGA -> HDMI

Lag Lag

• Direct loopback on laptop
• 22 frames, when 25 frames per second
• 0.8 Seconds

Better HDMI

• Expected to save 200ms

Video4Linux

• PI4 can handle 'YUYV'
• PI3 can handle 'MJPG'

  • Less on CPU
  • Poor display
  • Extra lag

v4l2-ctl -d 2 --list-formats-ext
            [0]: 'MJPG' (Motion-JPEG, compressed)
                    Size: Discrete 1024x768
                            Interval: Discrete 0.017s (60.000 fps)
            [1]: 'YUYV' (YUYV 4:2:2)
                    Size: Discrete 1024x768
                            Interval: Discrete 0.100s (10.000 fps)

OpenWRT

• Fast boot
• Instant Access point for Kindle(s)
• ~18,000 Packages available

  • opkg update
  • opkg install package_name

OkMonitor Image

• microSD Image: 300MB, 56MB compressed
• Wireless Access Point "OkMonitor"
• Headerless

  • Kindle connect and control

Netcat - nc

• Kindle has inbuild nc
• Kindle(s) and PI use nc
• Allows headless on PI, by nc

  • Pull ssh key
  • Configure monitor number to kindle
  • Restart broadcast - video stream

CPU Intensive

• Pixel by Pixel video encoding is intensive

  • Or my c is poor
  • Or both

• PI 3 not up to job

CPU Intensive

• PI are QUAD Core
• Video is encoded in kindle format

  • four streams 1/4 each
  • four raw2gmv to nc

QUAD Core

mkfifo /tmp/screen1.pipe
mkfifo /tmp/screen2.pipe
mkfifo /tmp/screen3.pipe
mkfifo /tmp/screen4.pipe

cat /tmp/screen1.pipe  | /usr/bin/raw2gmv  | netcat -l -p  5001 &
cat /tmp/screen2.pipe  | /usr/bin/raw2gmv  | netcat -l -p  5002 &
cat /tmp/screen3.pipe  | /usr/bin/raw2gmv  | netcat -l -p  5003 &
cat /tmp/screen4.pipe  | /usr/bin/raw2gmv  | netcat -l -p  5004 &

QUAD Core

ffmpeg -re -f v4l2 -input_format yuyv422  -y -video_size 1024x768  -i /dev/video0  \
    -pix_fmt gray -r 6 -f rawvideo  \
    -filter:v "crop=512:379:0:0,scale=512:379,transpose=2,transpose=2"  \
    /tmp/screen1.pipe  \
    -pix_fmt gray -r 6 -f rawvideo  \
    -filter:v "crop=512:379:512:0,scale=512:379"  \
    /tmp/screen2.pipe \
    -pix_fmt gray -r 6 -f rawvideo  \
    -filter:v "crop=512:379:0:379,scale=512:379,transpose=2,transpose=2"  \
    /tmp/screen3.pipe  \
    -pix_fmt gray -r 6 -f rawvideo  \
    -filter:v "crop=512:379:512:379,scale=512:379"  \
    /tmp/screen4.pipe

GeekMaster Video

• Released 05-04-2012
• Will play pre-encoded video

  • 800x600 at 7 fps

raw2gmv.c

• Takes rawvideo and encodes to kindle format
• Modified to encode at 512x379

gmvplay.c

• Receives 512x379
• Each pixel writes to four pixels

gmvplay2singleHD.c

• Receives 512x379
• Command line determines which quartile
• Each pixel writes to one pixel