Media Gateway Cache Switching Between Unicast and Multicast Delivery
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Solution Overview
Problem
Current media delivery systems face inefficiencies in bandwidth use, particularly with live television programs, due to limited support for IP multicast delivery, leading to delays and video loss when client devices do not support multicast modes, and increased load on head-end servers during popular channels.
Innovation Solution
A media gateway device with a cache pre-filled via IP multicast serves media files via HTTP, utilizing a proxy cache and FCAST/NORM media streamer for error correction and seamless switching between unicast and multicast modes to ensure continuous and efficient delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If IP multicast is used to deliver live television programs, then bandwidth efficiency is improved, but compatibility with client devices is worsened
Solution Approach 1:
The patent introduces a gateway device as an intermediary between the multicast delivery system and client devices. The gateway receives media files via IP multicast and serves them to client devices via HTTP unicast, thus mediating between the multicast infrastructure and unicast-capable clients, resolving the compatibility issue while maintaining bandwidth efficiency
Solution Approach 2:
The patent segments the media delivery function into two parts: the multicast delivery path (from head-end to gateway) and the unicast serving path (from gateway to client). This segmentation allows the system to leverage multicast for efficiency while using unicast for compatibility, as each segment can operate independently with its own protocol
2Speed
If a cache is pre-filled via IP multicast, then media file delivery speed is improved, but delivery reliability is worsened
Solution Approach 1:
The gateway pre-fills its cache with media files received via IP multicast before client devices request them. This preliminary action ensures that when clients request media files, they are already available in the gateway cache for immediate unicast delivery, thus improving delivery speed
Solution Approach 2:
The patent implements a feedback mechanism where the gateway monitors which media files are requested by client devices and adjusts its cache refilling behavior accordingly. When a media file is requested but not found in cache, the gateway fetches it from the multicast stream or alternate servers, creating a feedback loop that improves both speed and reliability
3Speed
If UDP is used for IP multicast delivery, then delivery speed is improved, but error correction capability is worsened
Solution Approach 1:
The patent changes the transport protocol parameter from UDP (connectionless, faster, but unreliable) to TCP (connection-oriented, slower, but reliable) for the gateway-to-client unicast delivery path. This parameter change allows the system to achieve both speed (via efficient multicast) and reliability (via TCP fallback)
4Loss of energy
If single packet loss occurs in UDP multicast, then bandwidth efficiency is improved, but video quality is worsened
Solution Approach 1:
The patent implements beforehand cushioning by having the gateway cache media files proactively before packet loss occurs. When packet loss happens in the UDP multicast stream, the gateway can still serve clients from its cache, cushioning against the impact of packet loss and maintaining video quality while preserving bandwidth efficiency
Data Source
AI summary
A file server delivers media files in unicast mode to a media gateway device in response to user requests, and a FCAST/NORM media streamer delivers a stream of these media files in multicast mode to the media gateway device. By using a file server operating in unicast mode and a FCAST/NORM media streamer delivering a stream of these media files in multicast mode, it is possible to switch seamlessly between the two modes in an embodiment. In an embodiment of the invention, a media gateway device includes a cache memory for storing media files from the file server and/or the FCAST/NORM media streamer; and a controller that controls delivery of media files from the cache memory to the user and transmits user requests for media files to the file server when the cache memory does not contain the media files requested by the user. Thus, the controller requests media files from the file server only when the media files requested by the user are not cached. Otherwise, the media files requested by the user are fetched from the cache memory for delivery to the user. In this manner, the media files requested by the user will be delivered by the file server in unicast mode only when the FCAST/NORM media streamer has not supplied such files to the gateway device for caching.