The research activities at the USC Data Management Research Lab and the Information Laboratory during the past several years have resulted in the design, implementation and evaluation of Yima, a scalable real-time streaming architecture that enables applications such as video-on-demand and distance learning on a large scale. Yima incorporates lessons learned from first generation research prototypes and it also complies with industry standards in content format (e.g., MPEG-2, MPEG-4) and communication protocols (RTP/RTSP).

The Yima server is based on a scalable cluster design. Each cluster node is a off-the-shelf personal computer with attached storage devices and, for example, a Fast Ethernet connection. The Yima server software manages the storage and network resources to provide real-time service to the various clients that are requesting media streams. The following is a list of features of the Yima system.

_{Commercial, off-the-shelf hardware components}

_{Scalable, multi-node implementation}

_{Smoothing for variable bit-rate (VBR) media}

_{Support for panoramic video and multi-channel audio}

_{Multi-channel synchronization}

_{Random data placement for load-balancing}

_{Deadline driven scheduling}

_{Support for heterogeneous disk systems (HERA)}

_{Online, incremental storage scalability (SCADDAR)}

The Yima clients run on either Windows or Linux and may utilize a hardware or software decoder to display media streams. We have implemented a number of different clients that support a variety of display bandwidths from less than 1 Mb/s to more than 20 Mb/s. The following media types are currently supported:

• DVD (MPEG-2 video, Dolby Digital (AC3) audio) at 5-8 Mb/s
• HDTV (MPEG-2 video, Dolby Digital (AC3) audio) from 19.4 Mb/s to 45 Mb/s.
• DivX;-) (MPEG-4 video and MP3 audio) at 600-800 Kb/s
• Panoramic video (5 MPEG-2 video channels frame accurately synchronized) at a total of 25 Mb/s
• Multi-channel audio (up to 16 channels of uncompressed PCM audio sample accurately synchronized) at a total of 10.8 Mb/s

The Yima continuous media server project has motivated a number of different sub-projects that are aimed at improving various aspects of the Yima system.

• Online Scalability: How do we scale the storage system incrementally while (a) the system continues operation, (b) the minimal amount of data is reorganized, and (c) the system continues to be load balanced.
• Heterogeneous Disk Storage: How do we maximize the resource use of disks with different data transfer rates and storage sizes while at the same time ensuring that none of the real-time constraints for audio and video data retrievals are violated.
• Variable Bitrate (VBR) Media: Constant bitrate (CBR) encoding of media streams can result in either reduced quality of complex scenes or wasted storage space during simple scenes. VBR encoding on the other hand allocates bits where they are most needed, resulting in a more uniformly high visual or aural quality. The disadvantage of the VBR technique is that it results in bursty network traffic and uneven resource utilization when streaming media. Our techniques focuses on smoothing VBR media transmissions without a priori knowledge of the actual bitrate. Hence, our technique can be applied to (a) live streams and (b) stored streams without requiring any server side pre-processing.

Furthermore, Yima is the basis of the Remote Media Immersion (RMI) project. RMI is a testbed that integrates many of the technologies that are the result of multiple research efforts. The goal of the RMI is to reproduce the complete aural and visual ambience of an environment that includes people and other real and virtual elements.

We have performed experiments across both LAN and WAN environments. Our most recent tests were conducted via a trans-continental SUPERNET link from the Information Science Institute (ISI East) at Arlington, VA, to the USC campus in Los Angeles, CA. See also the SUPERNET Next Generation Internet (NGI) Experiments web site.

• On Thursday May 9, 2002, the Yima streaming architecture was described in the The New York Times. The article entitled "On Internet of the Future, Surfers May Almost Feel the Spray" by Eric A. Taub appeared in the Circuits section. The Yima project is the streaming technology that enables high fidelity Internet on-demand media transmissions such as demonstrated by the Remote Media Immersion (RMI) project.
  Article PDF (1,329 KB).
• On Thursday May 9, 2002, Yima and RMI were covered during the 10 o'clock news on NBC-4.
  
  • Press clip in QuickTime format.
• On Thursday May 9, 2002, Yima and RMI were covered during the 10 o'clock news on KTLA-5.
  
  • Press clip in QuickTime format (broadband speed).
  • Press clip in QuickTime format (modem speed).
• On Wednesday June 19, 2002, Yima and RMI were covered in USC's Daily Trojan. The article entitled "USC engineers develop new 3-D technology" by Sara Rodriguez appeared in the Summer Trojan.
  • Article PDF (40 KB).

• Kun Fu, Ph.D., (server design and multi-threshold rate control)
• Sahitya Gupta, M.S., (server distributed file system and streaming content preparation)
• Mehrdad Jahangiri, M.S., (clients, infrared remote control, and multi-threshold flow control)
• Nitin Nahata, M.S., (client hardware interfaces and streaming content preparation)
• Vasan R. Sundar, M.S., (selective retransmission protocol)
• Rishi Sinha, Ph.D., (selective retransmission protocol)
• Didi Shu-Yuen Yao, Ph.D., (server design and scalability)
• Farnoush Banaei-Kashani, Ph.D., (RTSP design and implementation)
• Beomjoo Seo, Ph.D., (HDTV and multichannel audio interface)
• Guanghua Gary Zeng, M.S., (HDTV content preparation)
• Kambiz Ghahremani Sarighieh, M.S., (Demo video preparation)

The Yima technology has been licensed. More information can be found at USC's Office of Technology Licensing.

• Information Laboratory Yima page at USC.
• NSF ITR report page.
• One page Yima summary (PDF format, 28 KB).

• DivX is an MPEG-4 style codec.
• Creative Dxr2 and Dxr3 DVD hardware decoder Linux drivers.
• mpeg2dec, a fast, open source Linux MPEG-1 and MPEG-2 software video decoder.
• Panoram Technologies, home of the FullView 360 degree camera.
• Vela Research, home of the CineCast and CineCast HD hardware MPEG-2 decoders.
• RME, home of the multi-channel RME 9652 "Hammerfall" sound card.
• RTP: the Real-Time Protocol for streaming media.

Get the PDF reader from Adobe.

For additional publications see the following project pages: Continuous Media Storage, Advanced Media Transmission, and Remote Media Immersion.

• Yima: A Second Generation Continuous Media Server.
  Cyrus Shahabi, Roger Zimmermann, Kun Fu, and Shu-Yuen Didi Yao.
  Published in the IEEE Computer magazine, June 2002, pp. 56-64.
  Abstract Postscript (3,783 KB) PDF (913 KB)

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• Yima: Design and Evaluation of a Streaming Media System for Residential Broadband Services.
  Roger Zimmermann, Kun Fu, Cyrus Shahabi, Didi Yao, and Hong Zhu.
  Proceedings of the VLDB 2001 Workshop on Databases in Telecommunications (DBTel 2001), Rome, Italy, September 10, 2001.
  Abstract Postscript (65 KB) PDF (99 KB)
  

Maintained by Roger Zimmermann
Last updated: Thursday January 2, 2003.
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