1. 1
Screencasting
Rex Tsai
chihchun@kalug.linux.org.tw
http://nutsfactory.net/
H4 @ MR Brown
2013-08-29
(2013-09-01 updated)

2. 2
Screen mirroring solutions
● AirPlay
● mirroring standard for iOS.
● Miracast/WiDi
● RTP/RTSP
● Chromecast
● DIAL
● WebRTC

3. 3
Apple AirPlay
● Wireless Media Streaming / Screen Mirroring Protocol
for iOS
● Discovery – Bonjour / zeroconf
● AirPlay service / RAOP (Remote Audio Output Protocol)
● FairPlay for protect screen content and encrypted
● UDP-based, based on RTSP
● Codec - Apple Lossless codec with 44100 Hz and 2 channels
and H264
● Proprietary protocol, only license audio-streaming to 3rd
partyies

4. 4
Requirement for hacks
● Understand FairPlay / DRM for screen
protection
● FairPlay DRM initiation - ‘/fp-setup’
● Video steaming encryption
● AirTunes/AirPlay private/public RSA keys
● Implement the AirPlay receiver server

5. 5
Commerical products of
AirPlay mirroring
● James Laird reverse-engineered and released the
private key
● VMLite rPlay for Raspberry Pi and Windows
– http://www.youtube.com/watch?v=aviPOINM6Bk
● Electroniccolor -
http://v.youku.com/v_show/id_XNTgwMjQzMTk2.html
AirParrot - http://www.airsquirrels.com/airparrot/
● AirServer - http://www.airserver.com/
● Hacksugar: Live AirPlay mirroring to Mac from iOS |
TUAW - The Unofficial Apple Weblog
– http://www.tuaw.com/2012/02/08/hacksugar-live-airplay-mirroring-to-mac/

6. 6
Micrast/Wireless Display
● Discovery - WiFi Direct (Layer 2 protocol)
● Media Protocol
● RTP
● RTSP
● Available
● Android 4.2
● Windows client available from Intel
● Built-in in Windows 8.1
● Wi-Fi Display Technical Specification 199USD

7. 7

8. 8

9. 9

10. 10

11. 11
AOSP Miracast Sink
● Android 4.2
● https://github.com/kensuke/How-to-Miracast-on-AOSP/wiki
● https://github.com/kensuke/
● Demo - http://www.youtube.com/watch?v=KNEmaIr3FEg
● Possible to port this feature to Android dongle like mk802

12. 12
Chromecast
● DIscovery And Launch http://www.dial-multiscreen.org/
● Based on UpnP & REST
● WebRTC http://www.webrtc.org/
● Support applications
● YouTube
● Netflix
● Google Play Music
● Google Play Movies & TV
● “Google Cast” Browser plugin available for Windows, Mac OS,
Linux. https://chrome.google.com/webstore/detail/google-cast/boadgeojelhgndaghljhdicfkmllpafd
● Bootloader is hacked http://wiki.gtvhacker.com/index.php/Google_Chromecast#Bootloader_Exploit_Package
●
Does not work in AP Isolation mode
https://support.google.com/chromecast/answer/3213084?hl=en

13. 13
Supported Media Types
● Video codecs: H.264 High Profile Level
4.1, 4.2 and 5, VP8
● Audio decoding: HE-AAC, LC-AAC,
CELT/OPUS, MP3
● Containers: MP4/CENC, WebM,
MPEG-DASH, SmoothStreaming
● Level 1 DRM support: Widevine,
Playready
https://developers.google.com/cast/supported_media_types

14. 14

15. 15

16. 16
Chromecast clone Software
● SINK (Server)
● CheapCast - https://github.com/mauimauer/cheapcast
– Supported Applications
● ChromeCast
● YouTube
● PlayMovies
● GoogleMusic
● GoogleCastSampleApp
● GoogleCastPlayer
● Fling
● TicTacToe
– Unstable, Android's WebView does not work well on old device like mk802.
● SOURCE (Clients)
● AirCast
● RemoteCast

17. 17
References
● Unofficial AirPlay Protocol Specification
http://nto.github.io/AirPlay.html
● Wi-Fi Display Technical Specification v1.0.0
http://www.wi-fi.org/knowledge-center/published-specifications
● Stream Laptop Content over HDTV with Intel® Wireless Display
https://www-ssl.intel.com/content/www/us/en/architecture-and-technology/intel-wireless-display.html
● https://www.wi-fi.org/sites/default/files/uploads/wp_Miracast_Industry_20120919.pdf
● DIAL-2ndScreenProtocol-1.6.4.pdf http://www.dial-multiscreen.org/dial-protocol-specification
● Google Cast API https://developers.google.com/cast/