Electrical computers and digital data processing systems: input/ – Input/output data processing – Data transfer specifying
Reexamination Certificate
1999-05-07
2001-02-06
Lee, Thomas C. (Department: 2782)
Electrical computers and digital data processing systems: input/
Input/output data processing
Data transfer specifying
C710S033000, C710S052000, C710S053000, C710S057000
Reexamination Certificate
active
06185636
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to media server and/or video server systems, and more particularly to a media server system comprising a video server coupled through a SCSI bus to one or more MPEG decoder blocks, wherein the system pre-fills data buffers at start-up to prevent buffer underflow.
DESCRIPTION OF THE RELATED ART
Video-on-demand or video delivery systems enable a plurality of subscribers or users to selectively watch movies or other audio/video sequences which are stored on one or more video servers or media servers. The video servers are connected through data transfer channels to the plurality of subscribers or users. The video servers store a plurality of movies or other audio/video sequences, and each user can select one or more movies from the video servers for viewing. Each user includes a television or other viewing device, as well as associated decoding logic, for selecting and viewing desired movies. When a user selects a movie, the selected movie is transferred on one of the data transfer channels to the television of the respective user.
Full-motion digital video requires a large amount of storage and data transfer bandwidth. Thus, video-on-demand systems use various types of video compression algorithms to reduce the amount of necessary storage and data transfer bandwidth. Current video-on-demand systems use MPEG or MPEG-2 encoding in order to reduce the required data transfer bandwidth. Thus, audiovisual sequences, such as movies or other content, are stored on the media server in an MPEG compressed format, and the audiovisual sequence is decoded and typically converted to analog format for display and/or transmission to a user.
One type of media server design comprises a video server computer system which stores a plurality of encoded data streams, wherein this computer system is coupled through a SCSI (Small Computer Systems Interface) bus to one or more MPEG decoder blocks. Each of the MPEG decoder blocks are in turn coupled to video encoders and/or codecs (coder/decoders) for producing analog baseband data. Respective modulators may also be provided for modulating the data with a carrier frequency to produce band pass signals, such as UHF or VHF signals, or cable TV signals.
Media servers which utilize a SCSI bus to communicate to multiple MPEG decode channels utilize a single control channel for multiple video channels. The firmware overhead involved with beginning the transfer of video data on one or more channels may lead to data starvation of an existing channel. In other words, a buffer which is transferring data to an MPEG channel may run out of data due to the overhead associated with other channels. This may result in an undesirable interruption of the play of a multimedia stream. Therefore, a system and method is desired to reduce the probability of data starvation or underflow in a media server system.
SUMMARY OF THE INVENTION
The present invention comprises a media server system and method for reducing the probability of data starvation or underflow in a media server system. The media server system preferably comprises a video server computer system which stores a plurality of encoded data streams, wherein the computer system is coupled through a SCSI (Small Computer Systems Interface) bus to one or more MPEG decoder blocks. The media server system thus utilizes a single control channel for multiple video channels. As discussed above, the firmware overhead involved with starting channels can sometimes lead to data starvation of an existing channel. The present invention operates to fill the FIFO buffer of a channel to a higher level only during startup, thus reducing the probability of data underflow.
According to the invention, the host computer or server begins data transmission prior to sending the “play” function or play command. The number of blocks is calculated based on block size to prevent overflowing the buffer. In this embodiment, the MPEG decoder block is configured to not begin emptying the FIFO until the play function is decoded. After the pre-determined number of blocks have been transferred or issued, the play function is sent. This signals the firmware executing on the MPEG decoder block to enable the FIFO for transfer to the decoder. All subsequent transfers proceed normally.
In another embodiment where the host server is not configured to pre-load the buffer prior to issuing the play command, the firmware executing on the MPEG decoder block sets a flag to disable the FIFO buffer when the play command is received. The MPEG decoder also initiates a predetermined buffer block counter when the play command is received. As data blocks are received for the respective channel, the MPEG decoder decrements the block counter. The buffer block counter counts a predetermined number of blocks of received data based on worst case block size and buffer capacity. When the count expires, the MPEG decoder resets the play flag and enables the FIFO to begin transfers. Once the play flag is reset, all subsequent blocks proceed normally.
Therefore, the present invention pre-loads the FIFO buffer to prevent underflow problems associated with the start-up of multiple data streams. In one embodiment, the host server transfers a calculated number of SCSI blocks and used uses the “play” function or play command to terminate the preload process. In a second embodiment, where the host is not configured for the pre-load option, firmware in the target device detects the beginning of a transfer and use a block counter to control the pre-load process prior to execution of the play command.
REFERENCES:
patent: 5363138 (1994-11-01), Hayashi et al.
patent: 5502494 (1996-03-01), Auld
patent: 5584041 (1996-12-01), Odawara et al.
patent: 5600366 (1997-02-01), Schulman
patent: 5600573 (1997-02-01), Hendricks et al.
patent: 5619341 (1997-04-01), Auyeung et al.
patent: 5644787 (1997-07-01), Nakamura et al.
patent: 5708846 (1998-01-01), Ryan
patent: 5915094 (1999-06-01), Kouloheris et al.
“Buffer Management for Video Database Systems,” Rotem, et al., IEEE, pp. 439-448.
“A Multimedia Storage System for On-Demand Playback,” Oyang, et al., IEEE, pp. 53-64.
Conley Rose & Tayon PC
Kowert Robert C.
Lee Thomas C.
Perveen Rehana
Sun Microsystems Inc.
LandOfFree
Media server system and method for preventing FIFO buffer... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Media server system and method for preventing FIFO buffer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Media server system and method for preventing FIFO buffer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2575324