1. www.novocaptis.com WPSS Phase 2 Audio/Video Hardware & Software Architecture Christos Papachristou, Dipl-Eng, MSc, PhD

2. www.novocaptis.com Helmet attachment Components –Camera –Omnidirectional microphone –Microcontroller –Push-button –LED driver –Light LEDs –Headphone jack –Microphone jack

3. www.novocaptis.com Helmet attachment

4. www.novocaptis.com Helmet attachment Connection cable USB D+90 Ω twisted pair USB D- 5V2 Amp GND2 Amp Microphoneshielded Headphonesshielded

5. www.novocaptis.com Software Main processing module –Gumstix Overo FireSTORM COM TI DM3730 800Mhz Cortex-A8 ARM TI C64xx DSP @ 660Mhz TPS65950 Audio and power management chip Marvell 88W8686 WiFi/Bluetooth module 512Mb low power RAM 512Mb NAND flash

6. www.novocaptis.com Software Ångstrøm Linux –All packages are cross compiled using the OpenEmbedded framework Software modules are described through recipes: Text files containing instructions on where to get the source, how to patch it, compile it and install it. It also defines its dependences on other software.Upon issuing of a build command, all dependencies are sorted out and compiled if necessary.

7. www.novocaptis.com Software Ångstrøm Linux –All packages are cross compiled using the OpenEmbedded framework A recipe can also be a definition of a whole image of an embedded system. All patches and changes in the software packages performed during phase 1 are described in a set of such recipes. Compiling of the complete operating system takes initially 4-5 hours and is accomplished by a single command. Incremental builds take much less.

8. www.novocaptis.com Software Ångstrøm Linux –All packages are cross compiled using the OpenEmbedded framework The environment consists of two branches: One maintained by the OpenEmbedded or related communities and one which has user additions. Software developed during phase 1 has been maintained as such a branch in an SVN repository. In phase 2 this is scheduled to be maintained in git.

9. www.novocaptis.com Software Main software patches during phase 1 Kernel 2.6.34 –Power management functions of the TPS65950 chip –OTG USB power override –Camera sensor driver Linphone –Audio buffer optimisation for TPS65950 Gstreamer plugins –Camera drivers

10. www.novocaptis.com Software Main services (ARM) OpenVPN –For static IP acquisition to override CERN wireless device policies. Wireless network daemon –Set of scripts to handle reconnections during handover or temporal loss of signal

11. www.novocaptis.com Software Audio services (ARM) Linphone daemon Command script –A bash script that watches the state of the GPIO pins connected to the buttons assigned to the following actions: Volume UpSends command to ALSA mixer Volume DownSends command to ALSA mixer Call/Hang Up Sends command to Linphone daemon

12. www.novocaptis.com Software Audio services (Server) Asterisk server –Telephone book register between the mobile clients. Possible connection with CERN telephone network. Audio services (Supervision post) Linphone or other VoIP solution

13. www.novocaptis.com Software Streaming and Receiver services –Gstreamer pipeline The gstreamer libraries provide APIs both for prototyping and production code. During phase 1 only prototyping code was used in order to test the various pipeline elements and select among the most suitable for the specifications of the WPSS.

14. www.novocaptis.com Software Streaming and Receiver services –Gstreamer pipeline Flexibility is quite limited in the prototyping APIs and particularly regarding to reconnections, which happen often in the ATLAS cavern. The services are currently coded in C++ and maintained in a git repository

15. www.novocaptis.com Software Video services –Streaming service (ARM) –Receiver service (Server) –Transcoding service (Server)

16. www.novocaptis.com Software

17. www.novocaptis.com Software

18. www.novocaptis.com Software Streaming service (ARM) –Gstreamer pipeline –Video4Linux2 source element  Handling of Video4Linux2 IOCTLS for exposure –Colour conversion element  Employment of the ISP or DSP to handle more than 10-15 fps. –H264 encoding element  DSP code to achieve better than 752x532 resolution. –Packetisation and transmission element  Robust acknowledged communication

19. www.novocaptis.com Software Receiver service (Server) –Gstreamer pipeline –Reception and depacketisation element –H264 decoding element –Image processing/overlaying element –Input selector element –Video4Linux sink element

20. www.novocaptis.com Software Transcoding service (Server) –VideoLan Client server Input from video loopback device Transcoding into –MJPEG –H264 in MPEG4 TS  served as a file through HTTP  as an HTML video stream, after being split into 10 second chunks

21. www.novocaptis.com Software Transcoding service (Server) –VideoLan Client server The MJPEG stream is low delay and high bandwidth which better suits the needs of the supervisor post H264 has higher delay and low bandwidth and is better suited for storage. –A video file is constantly output by the server. An external application can get it through HTTP and store it if needed for archiving purposes –The HTML video streaming service provides a comparable capability

22. www.novocaptis.com Software Implementation roadmap Baseline system with main components in C++ –Production level code requires much more error- correction capabilities, in order to be maintenance free and robust –Faster performance Colour conversion, H264 encoding/decoding can be optimised on the hardware. Because of the modular design, they can be dealt with after the baseline system has been validated

23. www.novocaptis.com Software Thank you