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Method for seamless transitions between video decoders

IP.com Disclosure Number: IPCOM000018765D
Publication Date: 2003-Aug-06
Document File: 3 page(s) / 44K

Publishing Venue

The IP.com Prior Art Database


Disclosed is a method for seamless transitions between video decoders. Benefits include improved performance and improved usability.

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Method for seamless transitions between video decoders

Disclosed is a method for seamless transitions between video decoders. Benefits include improved performance and improved usability.


        � � � � � In the future, home audio-visual systems will stream video between clients in a person’s house to enable the enjoyment the content in any room of the house. Video content may be available from personal computers, digital video recorders, media centers, and set-top boxes. Content sinks will enable digital video content to be displayed on a television screen or a PC monitor. These sinks are often referred to as media adapters or thin clients. Video data can be transmitted between sources and sinks across networks through a streaming server that exists on the source device.

        � � � � � As the bandwidth available on the home network varies, the streaming server may switch between multiple versions of the same video sequence to match the network characteristics. For example, if a majority of a 100-Mbps Ethernet network is available, the server may send an 8 Mbps video stream. If other network traffic comes on line and the available bandwidth decreases to 20 Mbps, the server may scale back its usage and send a video stream at 4 Mbps.

        � � � � � Changing between bit rates can be performed in several ways. The server can specify rate control parameters to an encoder or transcoder. By changing the rate control parameter, the bit rate of the video sequence changes, but its properties remain the same. For example, the server may change a standard definition (720 x 480), MPEG 2 video signal from 8 Mbps to 4 Mbps by changing the rate control parameter. The decoder in the thin client can still decode the video stream without change to the display of the decoded video.

        � � � � � Alternatively, to get a better visual quality, the server may alter the resolution and/or compression algorithm as well as the bit rate. For example, the server may change a 720 x 480 MPEG2 signal at 8 Mbps to a 352 x 480 MPEG2 signal at 2 Mbps or a 352 x 480 MPEG4 signal at 1 Mbps.

        � � � � � When the resolution of the video is changed, the decoder may need to be reinitialized before decoding the changed compressed signal. When the video coding standard is changed, a different hardware or software encoder must be instantiated. In either case, the reinitialization or restarting of the decoder may result in a glitch in the presentation of the video.

        � � � � � In a conventional decoding system, two compressed video signals are received from the streaming server (see Figure 1). Incoming timing information is present and encapsulated in the form of network protocols (such as RTP or RTSP) or MPEG transport protocols (such as MPEG2 systems). The incoming timing information is used to pace the system and ensure that the decoding, scaling, and alpha blending between the streams is synchronized. Two video decoders operate in parallel. The first decodes compressed video A, which is the ori...