System and method for seamless switching through buffering
View Patent ↗A method of preparing data streams to facilitate seamless switching between such streams by a switching device to produce an output data stream without any switching artifacts. Bi-directional switching between any plurality of data streams is supported. The data streams are divided into segments, wherein the segments include synchronized starting points and end points. The data rate is increased before an end point of a segment, to create switch gaps between the segments. Increasing the data rate can include increasing a bandwidth of the plurality of data streams, for example by multiplexing, or compressing the data. The present invention can be used, for example, with MPEG or AC-3 encoded audio and MPEG encoded video segments that are multiplexed into MPEG-2 transport streams. Also included are specific methods for preparing MPEG video streams and multiplexing MPEG video with MPEG or AC-3 audio streams to allow a receiver to create seamless transitions between individually encoded segments.
1. A method of preparing a plurality of digital data streams, each data stream comprising multiple segments, said plurality of digital data streams to be received by a switching device, said switching device including a buffer with a predetermined capacity, said method comprising the steps of:
encoding said segments for transmission to said switching device at a selected data transfer rate, wherein said step of encoding said segments is performed based on a buffer capacity value that is less than said predetermined capacity of said buffer of said switching device; and
multiplexing said segments at said selected data transfer rates, wherein said encoded segments include synchronized start and end points in said plurality of digital data streams and wherein said step of multiplexing said encoded segments is performed at a second data transfer rate that is higher than said selected data transfer rate.
2. The method of claim 1 wherein said step of multiplexing said encoded segments at a second data transfer rate that is higher than said selected data transfer rate is performed for an entire duration of said encoded segments.
3. The method of claim 1 wherein said step of multiplexing said encoded streams at a second data transfer rate that is higher than said selected data transfer rate is performed for a portion of said encoded segments.
4. The method of claim 1 including the steps of:
appending additional data to said segments;
encoding said segments that include the appended additional data; and
removing said encoded additional data from said encoded segments.
5. The method of claim 1 , wherein said segments include MPEG encoded data streams.
6. The method of claim 5 , wherein said segments are multiplexed in an MPEG transport stream.
7. The method of claim 1 , wherein said plurality of digital media streams include AC-3 encoded data streams.
8. The method of claim 1 , wherein a gap is created following said synchronized end points.
9. The method of claim 1 wherein said segments are digital audio streams, and wherein said multiplexing of said encoded streams includes multiplexing at a buffer capacity value lower than said predetermined capacity of said buffer.
10. The method of claim 1 wherein said switching device buffer is an MPEG VBV buffer or a video decoding buffer in a set-top box.
11. The method of claim 1 wherein said switching device is a device capable of decoding MPEG-2 streams; a digital set-top box; a digital TV set; a Video-On-Demand Server; or a DVD player.
12. A system for creating an MPEG transport stream from a plurality of digital data segments, wherein said digital data segments have synchronized end points with respect to each other, and wherein said MPEG transport stream will be received by a switching device with a buffer, comprising:
a frame encoder to receive said plurality of digital data segments and encode said digital data segments into frame encoded segments, wherein said frame encoder encodes said digital data segments based on a selected capacity of said buffer;
a multiplexer coupled to said frame encoder to receive said frame encoded segments and create said MPEG transport stream, wherein said multiplexer adjusts a data rate of said frame encoded segments in said MPEG transport stream to allow a gap after said digital data segments with synchronized end points.
13. The system of claim 12 wherein said multiplexer adjusts a data rate of said frame encoded segments in said MPEG transport stream to a higher data rate for an entire duration of said segments.
14. The system of claim 12 wherein said multiplexer adjusts a data rate of said frame encoded segments in said MPEG transport stream to a higher data rate for a portion of said segments.
15. The system of claim 12 wherein said selected capacity of said buffer is a value below an actual capacity of said buffer.
16. The system of claim 12 wherein said frame encoder encodes said digital data segments as if said segments did not have end points.
17. The system of claim 12 wherein said digital data segments include digital audio streams, and wherein said multiplexer creates said MPEG transport stream based on a selected capacity of said buffer being a value below an actual capacity of said buffer.
18. The system of claim 12 wherein said switching device buffer is a MPEG VBV buffer or a set-top box video decoder buffer.
19. The system of claim 12 wherein said switching device is a device capable of decoding MPEG-2 streams; a digital set-top box; a digital TV set or a DVD player.