Transcript DIF
DV over IP Team 18 Björn Thorsén Hallberg Eva Codina Sanuy Fredrik Blomqvist Johan Fredriksson Tobias Karlsson May 2000 Agenda • • • • • Overview Technologies used Business ideas Video Questions DV over IP Main goal: develop a Remote Lecture System using DV on Linux Platforms RTP CIP DIF DIF DIF DIF DIF DIF DIF DV Server FireWire IP network UDP socket RTP DIF DIF DIF DIF DIF DIF DIF DV Client RTP CIP DIF DIF DIF DIF DIF DIF DIF DV Server FireWire IP network UDP socket RTP DIF DIF DIF DIF DIF DIF DIF DV Client Digital Video (DV) • provides high-quality video data • individual frame compression • supports NTSC and PAL video formats Digital Interface Format (DIF) (120.000 bytes) DV Frame (12.000 bytes) DIF sequence 0 Header Section DIF block 0 DIF block 1 DIF block 2 DIF sequence 1 Subcode Section VAUX Section DIF sequence n-1 Audio & Video Section NTSC: n=10 PAL : n=12 DIF block 149 FireWire (IEEE 1394) • High Perfomance Serial Bus • Characteristics: – Low cost – High-bandwidth • Topology: – Peer-to-peer protocol – Automatic bus configuration FireWire (IEEE 1394) cont. • Benefits: – – – – – – Guaranteed bandwidth Hot plugging Scalability Flexibility Universal interconnection Cable power Common Isochronous Packet (CIP) • FireWire supports isochronous transfer isochronous = equal time • isochronous data transfer – ensures constant data rate – time-dependent • 6 DIF blocks in each CIP packet GNU/Linux IEEE1394 Subsystem The driver hierarchy: Real-time Transport Protocol (RTP) • provides end-to-end delivery services for data with real-time characteristics • services: – timestamping – sequence numbering – payload type identification • “sublayer” of the transport layer Server application – DV Server Main program: There are two processes working with shared memory: – Read CIP packets from the FireWire – Send the DIF blocks encapsulated in RTP packets through the UDP socket to the IP network. Client application – DView • Functionality: decode and display DV data • Input: series of frames frame = full video image + 1/30 sec. sound + aux. data • Algorithm (3 steps) 1. Decode DIF blocks 2. Run iDCT (inverse-Discrete-CosineTransformation) luminance & chrominance 3. Convert YCrCb to RGB and draw the data on the screen Client application – DView Options to improve the perfomance: 1. Downscaling: reduces the displayed size of the video 2. Reduced rendering precision 3. Grayscaling: removes the need of: - decode and render the chrominance - convert from YCrCb to RGB KnowDV • The objective of the company: – provide real-time video transfers • How will we succeed? – – – – unique and useful products user-friendly interface consultant services multi-platform solutions DV Lecturing System • The product: DV Lecturing System – Cheap – High quality video – Multi-platform • Target groups: – Companies – Universities – Private users DV Lecturing System • Competitors: – No similar product for Linux platforms yet – Applications with less bandwidth requirement – Conferencing systems DV Lecturing System • Market segmentation: Questions ??