1、A MJPEG Encoder for the NOW to visualize and navigate on data-intensive scenarios,Jos Mara Gonzlez chemacs.berkeley.edu,The problem,Problem: How to be able to monitor through interactive visualization enormous amounts of image data that are being treated in a remote (parallel) machine from an extern
2、al box that controls the data process behavior. Two issues: link from the parallel machine to the controller is usually low bandwidth (at least parallel machine internal links) display performance,The solution,Solution: On-the-fly degradation (“downgrade”) of the data trading off visualization quali
3、ty to permit the adaptation to the control box display performance and link bandwidth. Some example numbers: ATV: 1920x1080, 30 fps, 1.5 B/pixel, 93 MB/s, cannot be pumped into a normal LAN CIF at 30 fps, 4.6 MB/s neither ATV with MJPEG 20/1 compression (q75) plus frame decimation (7.5 fps) get poss
4、ible bandwidth = 1 MB/s,More issues,Interactivity Scalability (no centralized coordination point) FlexibilitySolution: Parallelize the degradation process!,Parallelization,Parallel Architecture,An interesting application,A virtual-reality system that permits a remote user to navigate on very large i
5、mage assets (satellite, astronomical, geographical, medical, ) interactively. The user asks for images depending on its position. The system reads the data needed and encodes it in parallel, obtaining a video stream that fits in the user link.,Implementation,Three kinds of processes: readers encoder
6、s multiplexer Use of River, a data-flow programming environment and an I/O substrate for clusters of computers.,Implementation (cont.),Network of Workstations,River,Reader,Encoder,Mux.,Controlling scripts,River modules,Performance results,Disk performance IJG JPEG Encoder performance 2-3 MB/s Config
7、uration n/n/1 Be careful with file caches! (cleaner process),Performance results (cont.),TBD,ATV,CIF,QCIF,Conclusions,Efficient, scalable MJPEG encoder (1 MB/s of reading throughput per pair of nodes) Use of a parallel architecture to permit visualization of huge amounts of image data is an interest
8、ing tool to permit interactive monitoring of parallel machines. Design and development of a virtual-reality system based on the parallel MJPEG encoder,Future work,Output bandwidth adaptive to remote link MPI implementation instead of River Display app. problems: RTP / MPEG Prefetching policies Add DQ Finish the implementation of the system (some parts are still simulated).,
