System and method for transmitting video material

摘要

A "video fax" system electronically delivers a non-real time, full-motion, sub-broadcast quality facsimile of relatively short segments of video material from an originating location to a receiving location in a short period of time, utilizing selected widely available commercial telephone switched networks. At the originating location, analog source material is digitized, compressed, prepared for transmission and stored temporarily. Digital source material is handled by bypassing the digitization step and part of the compression step, and performing the necessary file conversion. The sending location dials up the receiving location, and a connection is established. The digital file is transmitted over the network. When finished, the connection is terminated. At the receiving location, the material is received, decompressed and converted back to either analog form or digital form, depending on the recipient's preference. Compression and decompression are each performed in two stages, with a real-time component performed at full-frame rate, and an offline secondary reduced frame-rate component. Alternatively, the compression is performed entirely at the reduced frame rate, which involves undoing of the compression component performed in real-time. The corresponding decompression involves decompressing entirely at a reduced frame rate, followed by recompressing in preparation for full-frame rate real-time decompression. Transmission over the telephone network is performed concurrently with the reduced frame rate compression, resulting in an overall faster transfer.