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WPSS Phase 2

WPSS Phase 2. Audio/Video Hardware & Software Architecture. Christos Papachristou, Dipl-Eng, MSc, PhD. www.novocaptis.com. Helmet attachment. Components Camera Omnidirectional microphone Microcontroller Push-button LED driver Light LEDs Headphone jack Microphone jack.

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WPSS Phase 2

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

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

  3. Helmet attachment www.novocaptis.com

  4. Helmet attachment • Connection cable www.novocaptis.com

  5. 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 www.novocaptis.com

  6. 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. www.novocaptis.com

  7. 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. www.novocaptis.com

  8. 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. www.novocaptis.com

  9. 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 www.novocaptis.com

  10. 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 www.novocaptis.com

  11. 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: www.novocaptis.com

  12. 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 www.novocaptis.com

  13. 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. www.novocaptis.com

  14. 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 www.novocaptis.com

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

  16. Software www.novocaptis.com

  17. Software www.novocaptis.com

  18. 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 www.novocaptis.com

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

  20. 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 www.novocaptis.com

  21. 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 www.novocaptis.com

  22. 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 www.novocaptis.com

  23. Software Thank you www.novocaptis.com

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