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A DSP-Based Platform for Wireless Video Compression

A DSP-Based Platform for Wireless Video Compression. Patrick Murphy, Vinay Bharadwaj, Erik Welsh & J. Patrick Frantz Rice University November 18, 2002. Motivations & Requirements. Wireless video communication Demand expected to explode Much more challenging than voice

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A DSP-Based Platform for Wireless Video Compression

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  1. A DSP-Based Platform for Wireless Video Compression Patrick Murphy, Vinay Bharadwaj, Erik Welsh & J. Patrick Frantz Rice University November 18, 2002

  2. Motivations & Requirements • Wireless video communication • Demand expected to explode • Much more challenging than voice • Standards not yet established • Need modular hardware & software • Testbed should approximate real system • Similar hardware • Portable code

  3. Testbed Description • Source coding on Texas Instruments DSP • Similar to processors in most wireless devices • Mature software development environment • Bluetooth wireless interface • Datarate comparable to future mobile systems • Decoding performed on separate PC

  4. Testbed Hardware • Custom hardware • Inspired by TI Imaging Developers Kit • Support for lower resolution imaging • Integrates wireless interface & host processor • Daughtercard to TI DSP Starter Kits • Adheres to DSK interface specification • Backward and forward compatible with DSKs

  5. Testbed Hardware Custom daughtercard on C6416 DSP board

  6. Hardware Details: Processor • Axis Etrax 100LX • 32-bit 100 MIPS RISC processor • Runs full Linux operating system • Uses 2.4.x kernels and glibc • Open source Bluetooth stack • Originally developed by Axis • Now available under GPL • Multichip Module • Integrated flash, SDRAM and Ethernet interface

  7. Hardware Details: Camera • Omnivision CMOS imager • 16-bit digital interface • Supports YUV 4:2:2 and raw RGB • On-board image preprocessor • Color space conversion • White balance • Configuration by I2C • Easily controlled by Etrax processor

  8. Hardware Details: Bluetooth • Support for variety of Bluetooth hardware • Up to 1 Mbps serial connection • Standard UART interface • SiliconWave and Ericsson modules tested • Flexible application-level interface • Simple (virtual) serial port • TCP/IP via PPP • Custom protocols possible

  9. Hardware Details: DSPs • Daughtercard adheres to TI spec • Compatible with C62x, C67x & C64x boards • Possible future use with C5x systems • Minimal resource requirements • Uses just one external interrupt • All transfers via external memory interface • Allows additional daughtercards to be used

  10. Software Tools • DSP software • Development in TI Code Composer • Compatible with CC 1.2x and 2.x • Only requires DSK tools • Uses dsplib and imglib • No third-party libraries or extensions required • Etrax software • Standard Linux development in C/C++ • GNU tools (gcc, gdb, etc.)

  11. Image Capture Dataflow • Each pixel read is read from the camera • Daughtercard buffers one line • EDMA interrupted for each line • Buffer emptied by EDMA burst read • EDMA buffers full frame • DSP interrupted for full frame • Frame used only if DSP is ready

  12. Transmission Dataflow • DSP writes coded data to memory • EDMA constantly writes to EMIF • Etrax on daughtercard reads data • Data packaged and transmitted

  13. Testbed Software • Generic framework for dataflow • EDMA setup optimized for input & output • Two coding schemes implemented • MPEG-4 • Advanced video compression • Designed for low-datarate applications • JPEG2000 • Advanced still image compression • Extremely good compression vs. quality

  14. MPEG-4 Encoder • Structure based on open source x86 code • Heavily optimized for C6x processors • Extensive use of TI assembly routines • Implements MPEG-4 Simple Profile • Only one previous frame required • Operates on 8 x 8 macroblocks • Minimizes internal data memory requirements • Core uses 57 KB of program memory

  15. MPEG-4 Encoder Performance • Depends heavily on cache configuration Encoder Performance on C6711

  16. JPEG2000 Image Compression • New version of popular JPEG standard • Continuous tone still image compression • Wavelet based algorithm • More computational intensive than JPEG’s DCT • Much better compression ratios • Useful features • Lossless and lossy options • Random access - no inter-frame dependence • Good control over quality vs. compression ratio

  17. JPEG2000 Encoder • Based on JasPer codec • Open source reference implementation • Project of Image Power & U of British Columbia • Very modular and abstracted design • Easy addition of features and formats • Great for PC execution • Bad for embedded DSP execution • DSP optimizations • Reduce function calls in core code • Eliminate some extraneous format flexibilities

  18. JPEG2000 Encoder Results • Operation on 32 x 32 pixel tiles • Constrained by DSP’s internal data memory • Total code size around 300KB • More internal program memory boosts performance Encoder Performance (frames/sec)

  19. Future Work: Hardware • Interface to new C55x DSP systems • Dependent on availability from TI • Further integrate components • Design single board system • Migrate wireless processing to DSP • TI’s OMAP platform is good candidate • Support full-duplex operation • Add audio support • Integrate video display

  20. Future Work: Software • Implement MPEG-4 decoder • Relatively easy compared to encoder • Further optimize JPEG2000 encoder • Reduce number of data structures • Minimize function calls • Migrate core to optimized assembly routines • Increase tile size to reduce DMA transfers • Investigate better error protection • Supplement or replace Bluetooth error control

  21. Conclusions • Modular & standards-based testbed • Realistic platform • Resembles capabilities of future mobile devices • It works! • Hardware manufactured and tested • Software framework validated • Two compression standards implemented • Ready for future research

  22. Questions ?

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