Media server system which employs a SCSI bus and which utilizes SCSI logical units to differentiate between transfer modes

Abstract: A media server system including a media server coupled through a SCSI bus to one or more MPEG decoder boxes. Each of the MPEG decoder boxes includes a plurality of data channels and is adapted to receive encoded MPEG data from the computer system. The computer system generates data transfers to the respective MPEG decoder boxes for transfer on the selected channels. The computer system is configurable according to various file storage formats, including file systems which prepend a header comprising channel information to the video data, and file systems which do not prepend a header comprising channel information to the video data. According to the present invention, the computer system assigns a first SCSI logical unit number, preferably LUN 0, to a SCSI bus data transfer if the data being transferred includes a header comprising channel information. The computer system assigns a SCSI logical unit number which corresponds to the destination channel if the data transfer does not include a header including channel information. Each of the MPEG decoder boxes examines received data from the computer system and uses the SCSI logical unit number comprised in the data to determine the channel. If the LUN is 0, the MPEG decoder box examines the header in the received data and determines the channel from the header. If the LUN is other than 0, the MPEG decoder box determines the channel based on the LUN number. Therefore, the present invention allows the MPEG decoder box to operate with different file systems.

Description: 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 utilizes SCSI logical unit addressing to identify channels in order to accommodate different file system architectures. 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 generally use a file system to store the video or media streams. Examples of a file system include the UNIX file system (UFS), the media file system (MFS) developed by Sun Microsystems, and the Windows NT file system developed by Microsoft Corporation, among others. Certain file system, such as the UNIX file system, incorporate or prepend header information to data, such as video data, which includes a function code as well as a channel number associated with the data. Other file systems, such as the media file system, do not prepend a header which includes this information to video data. Thus, if an MPEG decoder block is designed to accept data in a certain format, such as including or not including this prepended header, the MPEG decoder block typically will not work with the other type of file format. Therefore, an improved media server system and method is desired which includes MPEG decoder block logic that operates properly with different file system formats. SCSI Bus Background Background on the SCSI bus architecture is deemed appropriate. The SCSI bus is a peripheral expansion bus used for connecting peripheral I/O devices to a computer system. Various versions of the SCSI bus exist, including "Fast SCSI", "Wide SCSI", and "Fast/Wide SCSI". The Wide SCSI bus can accommodate up to 16 devices, including one or more host adapters and up to 15 other SCSI devices which are connected to the SCSI bus. The host adapter interfaces the computer system to the SCSI bus and controls operations on the SCSI bus. Devices on the SCSI bus are classified as target devices or initiator devices. Some SCSI devices may function as both target and initiator devices. A SCSI host adapter is the most common example of an initiator. Common examples of SCSI target devices are disk drives and tape drives. Each device connected to the SCSI bus includes a target ID or address. The target ID is used during arbitration and is asserted by its respective device to request ownership of the SCSI bus. The target IDs are also used during a selection phase in which a device winning arbitration of the SCSI bus selects another device on the SCSI bus for sending a command. A bridge controller may be connected to the SCSI bus, wherein the bridge controller couples to one or more other devices, referred to as logical units, which interface through the bridge controller to the SCSI bus. One example of a bridge controller is a SCSI to SCSI bridge controller which interfaces a first SCSI bus to a second SCSI bus. The one or more logical units connected to the bridge controller each have logical unit numbers for identification. The SCSI specification provides for logical unit numbers 0 through 7. In an exemplary SCSI protocol sequence in which a SCSI host adapter transfers data to a SCSI target, an initial bus free phase is followed by an arbitration phase. During the arbitration phase, each of the respective devices desiring to arbitrate for the bus, including the host adapter, asserts the data bit corresponding to its respective target ID. Once the host adapter wins arbitration, then, during a selection phase, the device which wins arbitration selects the target. After the selection phase, a message out (MSG_OUT) phase occurs, in which the host adapter sends an identify message and optional tag queue message and tag bytes to the target. The identify message includes three bits which identify the logical unit number (LUN) number for which the forthcoming command is destined. After the MSG_OUT phase, a command phase occurs. During the command phase, the host adapter sends out a sequence of bytes referred to as the command descriptor block (CDB) to the target. The CDB includes information about the upcoming transfer. The first byte of the CDB includes an opcode which indicates whether the upcoming transfer is, for example, a read or write. The second byte of the CDB comprises three bits of logical unit information, i.e., the LUN number. The command descriptor block thus also includes three bits which identify the logical unit number. After the command phase, a data out phase occurs in which the host adapter transfers the data specified in the CDB to the target. The target then sends a byte of status information to the host adapter during a status phase. Finally, the target sends a command complete message byte to the host adapter to indicate completion of the issued CDB and then releases the SCSI bus back to another bus free phase. If the SCSI data transfer involves a device which is not a bridge device, then the logical unit number is set to zero. However, if the transfer involves a bridge controller which couples to one or more devices which have logical unit numbers, then the three bits of information in the identify message and the second byte of the CDB include the logical unit number of the respective device involved in the transfer. In WO 94/30014 there is disclosed a media server system with plural decoders, each with plural channels. Summary of the Invention According to one aspect of the present invention there is provided a media server system, comprising: one or more decoder boxes, wherein each of said one or more decoder boxes includes a plurality of data channels; a computer system including a memory media for storing data and a host adapter for coupling to a bus, characterized in that the computer system is configured to generate data transfers of blocks of data to individual ones of the one or more decoder boxes through said bus, wherein the computer system is configured to assign a first value to a logical unit number to a field of a first of said data transfers targeting a first of the decoder boxes if a first block of data being transferred includes a header comprising channel information indicating a destination data channel from a plurality of data channels of the first decoder box, and wherein the computer system is configured to assign a value, corresponding to the destination data channel and different from said first value, to the logical unit number field of the first transfer if the first block of data being transferred does not include said header; wherein each of said one or more decoder boxes is adapted to receive a block of the data from said computer system in response to one of said data transfers targeting the decoder box and to transfer said received block of data on the destination data channel; and wherein each of said one or more decoder boxes is configured to determine the value contained in the logical unit number field of a transfer from the computer system, to determine the destination data channel from the channel information in the header of the received block if the value contained in the logical unit number field is the first value, and to determine (614) the destination data channel from the value contained in the logical unit number field if the value contained in the logical unit number field is not the first value. According to another aspect of the present invention there is provided a method for transferring data in a media server system comprising a video server, one or more decoder boxes, each comprising a plurality of data channels, and a cable connecting the video server to said one or more decoder boxes, the method being characterized by comprising: the video server reading a first block of data from a storage media; the video server configuring said first block of the data for transfer to a selected one of the one or more decoder boxes, wherein said configuring includes assigning a first value to a logical unit number field of the transfer if said first block of the data includes a header comprising channel information indicating a destination data channel from the plurality of data channels of the selected decoder box, and wherein said configuring includes assigning a value, corresponding to the destination data channel and different from said fibst value, to the logical unit number field of the transfer if said block of the data does not include said header, the video server performing said transfer of said first block of the data to said selected decoder box; said selected decoder box receiving said first block of data in response to said transfer; said selected decoder box determining value contained in the logical unit number field of said transfer; said selected decoder box determining the destination data channel from the channel information in the header of the first block of the data if the value contained in the logical unit number is the first value; said selected decoder box determining the destination data channel from the value contained in the logical unit numbers field if the value contained in the logical unit number field is different from the first value; said selected decoder box transferring the first block of the data on the destination data channel. The present invention comprises a media server system including a media server coupled through a SCSI bus to one or more MPEG decoder boxes. Each of the MPEG decoder boxes includes a plurality of data channels and is adapted to receive encoded MPEG data from the computer system. The computer system generates data transfers to the respective MPEG decoder boxes for transfer on the selected channels. The computer system is configurable according to various file storage formats, including file systems which prepend a header comprising channel information to the video data, and file systems which do not prepend a header comprising channel information to the video data. According to the present invention, the computer system utilizes the SCSI bus LUN field to indicate the presence or absence of a header comprising channel information. The computer system also utilizes the SCSI bus LUN field to provide channel information when no header is included. In the preferred embodiment, the computer system assigns a first logical unit number, preferably LUN 0, to a SCSI bus data transfer if the data being transferred includes a header comprising channel information. The computer system assigns a logical unit number which corresponds to the destination channel if the data transfer does not include a header including channel information. Each of the MPEG decoder boxes examines received data from the computer system and determines the logical unit number comprised in the data. If the LUN is 0, the MPEG decoder box examines the header in the received data and determines the channel from the header. If the LUN is other than 0, the MPEG decoder box determines the channel based on the LUN number. Therefore, the present invention allows the MPEG decoder box to seamlessly operate with different file system formats. Brief Description of the Drawings A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings in which: Figure 1 illustrates a media server system according to one embodiment of the present invention; Figure 2 illustrates a media server system according to another embodiment of the invention; Figure 3 illustrates a media server system which includes a plurality of 24 channel MPEG decoder units forming a 96 channel system; Figure 4 is a block diagram illustrating the MPEG decoder box of Figure 1; Figure 5 is a flowchart diagram illustrating operation of the media server computer system performing a transfer; and Figure 6 is a flowchart diagram illustrating operation of the MPEG decoder. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary the intention is to cover all modifications equivalents and alternatives solely within the scope of the present invention, which is defined by the appended claims. Detailed Description of the Preferred Embodiment Referring now to Figure 1, a diagram illustrating the media server system according to one embodiment of the present invention is shown. As shown, the media server system includes a computer system unit 102. The computer system unit 102 is preferably the Sun SS-5 or Sun SS-20 computer produced by Sun Microsystems, and is preferably based on the UltraSparc processor. The computer system unit 102 may include one or more various types of storage devices including a RAID (redundant array of inexpensive disks) disk array, one or more digital video disks, or other memory or media storage as desired. Alternatively, or in addition, the computer system unit 102 may couple to a disk array storage device 104, as shown. The computer system 102 may also include a monitor (not shown). The various media storage devices comprised in the computer system unit 102 or coupled to the system unit 102 preferably store compressed data streams. In the preferred embodiment, the data streams are MPEG-2 compressed streams. However, it is noted that any of various types of data or video compression may be used as desired. The computer system unit 102 couples to one or more MPEG decoder boxes 122 as shown. In the embodiment shown, the computer system unit 102 couples to four MPEG decoder boxes 122A - 122D. Each MPEG decoder box 122 preferably comprises 6 MPEG channels. The group of four MPEG decoder boxes 122A - 122D collectively comprises a 24 channel decoder unit 130. As shown, the MPEG decoder boxes 122A - 122D are preferably configured in a rack mounted configuration, wherein the plurality of MPEG decoder boxes 122 are mounted one on top of each other. The MPEG decoder boxes 122 are preferably connected in a daisy chained manner. The computer system unit 102 preferably couples to a first one of the respective MPEG decoder boxes 122A through the Small Computer Systems Interface (SCSI) bus or cable 112. As is well known, the SCSI bus is a peripheral device bus wherein a plurality of devices may be connected to the bus in a daisy chained manner. The SCSI bus may be the Fast SCSI bus or the Wide SCSI bus or a Fast/Wide SCSI bus, as is well known in the art. As shown, the computer system unit 102 couples to a first MPEG decoder box 122A, and the remaining MPEG decoder boxes 122 are in turn daisy chained together. The computer system 102 includes a SCSI host adapter (not shown) which couples through a SCSI cable to the MPEG decoder box 122A. Referring now to Figure 2, an alternate embodiment of the media server system is shown. In the embodiment of Figure 2, a single MPEG decoder 122 is connected to the media server system unit 102. The single MPEG decoder 122 and the media server system unit 102 are preferably physically configured in a rack mounted configuration. Although not shown in Figure 2, the MPEG decoder 122 couples to the media server system unit 102 through a SCSI connection or SCSI cable. The media server system unit 102 may in turn couple to a disk array media storage unit 104 or other type of storage unit, preferably through a Fast SCSI bus, or Fast-Wide SCSI bus cable 112A, as shown. Referring now to Figure 3, a block diagram illustrating a media server system according to another embodiment is shown. This embodiment includes four 24 channel MPEG decoder units 130 labeled 130A - 130D. In Figure 3, each of the 24 channel MPEG decoder units 130 comprises the four MPEG decoder boxes 122A - 122D connected or daisy chained together as shown in Figure 1. In the embodiment Figure 3, four 24 channel MPEG decoder units 130 are daisy chained together to produce a 96 channel system. Thus the embodiment of Figure 3 comprises 16 MPEG decoder boxes 122. As shown in Figure 3, in this embodiment the media server system unit 102 includes a plurality of output ports, preferably four output ports, which provide Fast / Wide SCSI bus connectivity. Each of the SCSI bus connector ports is adapted to couple to a digital input of one of the respective 24 channel MPEG decoder units 130A - 130D as shown. As shown, the media server system unit 102 also includes a serial output port which couples to an input port of one of the respective MPEG decoder units 130A. The respective MPEG decoder unit 130A which receives the serial output from the media server system unit 102 includes an analog output which is provided to a corresponding analog input of a subsequent MPEG decoder unit 130B. This respective MPEG decoder unit 130B in turn provides an analog output to an analog input of a subsequent MPEG decoder unit 130C. Finally, the MPEG decoder unit 130C provides a corresponding analog output to an analog input of the last MPEG decoder unit 130D. Thus, each of the MPEG decoder units 130A-D are daisy chained together through the serial output of the media server system unit 102. The last MPEG decoder unit 130D in the daisy chain provides a 96 channel output, i.e., an output signal which comprises up to 96 video streams or channels of video or audiovisual content, including television programming content. The analog output of the MPEG decoder unit 130D may be comprised in various formats. In one embodiment, the analog output conforms to the National Television Standards Committee (NTSC) standard for analog video. In an alternate embodiment, the analog output corresponds to the European PAL format. As shown in Figure 3, the first MPEG decoder unit 130A also preferably includes an analog input port for receiving an analog input signal. As shown, this analog input signal may comprise a UHF or VHF signal, or a cable TV signal. Figure 4 - MPEG Decoder Box Block Diagram Referring now to Figure 4, a block diagram illustrating one of the MPEG decoder boxes 122 is shown. As shown, each MPEG decoder box 122 includes an MPEG decoder board 180. The MPEG decoder board 180 includes two expansion slots 226 and 227 for receiving up to two MPEG decoder daughter cards 182. The MPEG decoder board 180 includes two MPEG channels, as shown. Each MPEG decoder daughter card 182 also includes two MPEG channels. Thus, when two MPEG decoder daughter cards 182 are inserted in the respective slots 226 and 227 of the MPEG decoder board 180, the MPEG decoder box 122 comprises 6 MPEG channels. The MPEG decoder box 122 also includes a modulator box 184 which is coupled to an output of the MPEG decoder board 180. The output of the MPEG decoder board 180 is a baseband signal. The modulator box 184 converts the output baseband signal to a passband signal, such as a UHF, VHF or cable TV signal. Each MPEG decoder board 180 includes an input/output (I/O) port 202 for coupling to a SCSI bus. As noted above, in the preferred embodiment each MPEG decoder box 122 is adapted for coupling to a Fast/Wide SCSI bus. As also noted above, the SCSI bus I/O port is preferably used to couple through a SCSI bus to a respective media server system unit 102. The SCSI I/O port 202 couples to a SCSI controller 204. In the preferred embodiment, the SCSI controller is the NCR53C720 SCSI Controller produced by National Cash Register (NCR). Each MPEG decoder box 122 also includes a serial port input for receiving serial data. The respective serial port input 212 couples to a local processor 214. In the preferred embodiment, the local processor 214 is the MC68340 processor produced by Motorola Corporation. The SCSI controller 204 and the local processor 214 couple to a system bus interface 222. A memory, preferably dynamic random access memory (DRAM) 216, couples to the system bus interface 222. The DRAM is preferably 512K x 16. A nonvolatile memory 218, preferably an EEPROM (electrically erasable programmable ROM), is also coupled to the system bus interface 222. The EEPROM 218 stores firmware which controls the operation of the SCSI controller 204 according to the present invention. At power on, the firmware stored in the EEPROM 218 is loaded into the DRAM 216, and the firmware is then executed by the SCSI controller 204 from the DRAM 216. As discussed below, the firmware directs the SCSI controller 204 to examine the Logical Unit # (LUN) during a video transfer and determine destination channel information, i.e., determine which of the six channels on which the data should be transferred. As discussed below, if the LUN is 0, then header information is included with the video data block which indicates the channel number. If the LUN is not 0, then no header is prepended, and the SCSI controller 204 uses the LUN to determine the appropriate MPEG channel. The system bus interface 222 couples to a bus 224 as shown. The two MPEG decoder daughter card slots 226 and 227 are coupled to the bus 224. The bus is preferably the S-bus, but other bus types may be used. Two MPEG decoder logic blocks 230 are coupled to the bus 224. The MPEG decoder logic blocks 230 are preferably identical, and only one is described below for convenience. As shown, each MPEG decoder logic block 230 includes a first transceiver 232 coupled to the system bus 224. A first in first out (FIFO) buffer 234 couples to the transceiver 232. Each of the transceiver 232 and FIFO buffer 234 couple to an MPEG-2 decoder block 242. A memory block 244, preferably 2M x 16 DRAM, couples to the MPEG-2 decoder block 242. The MPEG-2 decoder block is preferably the HDM8211 produced by Hitachi. The MPEG-2 decoder block 242 couples to a video encoder 252. The video encoder 252 includes analog to digital conversion logic and produces a baseband analog video signal. The MPEG-2 decoder block 242 also couples to an audio coder/decoder (codec) 254, which converts the digital audio portion of the decoded MPEG signal to analog audio signals. Each of the video encoder 252 and codec 254 are coupled through a bus to an input/output port 262 of the MPEG decoder board 180. As mentioned above, one or more MPEG-2 decoder daughter cards 182 may be coupled to the system bus 224 for providing two additional stream processing channels. As shown, each MPEG-2 decoder daughter card 182 comprises two MPEG decoder logic blocks 230, as described above. The analog I/O port 262 of the MPEG decoder board 180 preferably outputs a baseband analog signal comprising a plurality of data streams or channels. In the preferred embodiment of the invention, a modulator box 184 is coupled to the I/O outport 262 for converting the baseband analog signal to a band pass analog signal. As shown, the modulator box 184 comprises a plurality of modulators 284 for each of the respective channels. Each of the modulators 284 is coupled to a combiner 286 which combines the modulated systems into a single analog signal, such as a VHF or UHF signal, comprising a plurality of channels. The combiner 286 provides an output through a connector 288. The output may conform to any of various formats, including the NTSC format, the PAL format, or the SECAM format. As shown, the modulator box 184 also includes an input for receiving a UHF, VHF or cable TV signal. The analog input is provided to the combiner 286 and is provided as a portion of the analog output from the I/O port 288. Figure 5 - Flowchart Diagram of Media Server Referring now to Figure 5, a flowchart diagram illustrating operation of the computer system 102 according to the preferred embodiment of the invention is shown. As shown, when the computer system 102 is transferring video data or video streams to one of the MPEG decoder boxes 122, the computer system 102 first retrieves the data to be transmitted from the storage media. The computer system 102 then determines in step 504 if the video data block includes a prepended header. As noted above, certain file systems, such as the UNIX file system, prepend header information to a video data block, wherein this header information includes the MPEG channel number and the number of bytes involved in the transfer. The MPEG channel number is necessary for the MPEG decoder box 122, which is a multi-channel MPEG decoder, to properly route the video data to the proper MPEG channel. However, other file systems, such as the media file system (MFS), do not provide for header information to be prepended to a video data block. Therefore, in step 504 the computer system 102 determines if a prepended header is included with the video data block. If so, then in step 508 the host driver executing on the computer system 102 assigns logical unit zero (LUN 0), i.e., writes a 0 value in the LUN field of the command descriptor block of the transfer. As discussed further below, the LUN 0 value written into the command descriptor block indicates to the SCSI controller 204 in the MPEG decoder box 122 that the video data block includes a prepended header. The LUN 0 value is also preferably written into the identify message of the SCSI transfer. Upon completion of step 508, the host server 102 performs other operations necessary to perform the transfer, and then in step 512 the server 102 performs the data transfer to the respective MPEG decoder box 122 based on the target ID of the respective box. Operation then completes. If a prepended header is determined to not be included with the video data in step 504, then in step 506 the host driver executing in the computer system 102 assigns an LUN number in the command descriptor block which indicates the respective MPEG decoder destination channel. In the preferred embodiment, the computer system 102 assigns or writes one of LUNs 1-6, corresponding to one of the respective six channels of the MPEG decoder box 122. The channel data is thus encoded in the LUN field of the command descriptor block. The respective LUN number is also written into the identify message of the SCSI transfer. Each of the LUNs 1-6 have a one-to-one correspondence with the respective MPEG channel number on the MPEG decoder box 122. As discussed above with reference to Figure 4, the MPEG decoder box 122 includes at least two MPEG channels and may include up to six MPEG channels. Where a prepended header is not included, the MPEG channel number which is the destination for the data is written or encoded into the LUN field of the command descriptor block to enable the MPEG decoder box 122 to determine the channel number. After operation of step 506, the host server 102 performs other operations necessary to perform the transfer and then performs the data transfer in step 512. Figure 6 - Flowchart Diagram of MPEG Decoder Box Referring now to Figure 6, a flowchart diagram illustrating operation of the SCSI controller 204 in a respective MPEG decoder box 122 is shown. As shown, in step 602 the MPEG decoder box 122 receives data from the video server 102. This video write data is received in step 602 by the respective MPEG decoder box 122 in response to a transfer performed in step 512 of Figure 5. As discussed above, during a video data transfer, the video server will use a target ID or target address which indicates the respective MPEG decoder box 122 that is the destination for the video write being performed. In step 604 the SCSI controller 204 in the respective MPEG decoder box 122 determines the logical unit number (LUN). The SCSI controller 204 preferably determines the LUN from the command descriptor block (CDB) of the SCSI transfer. The LUN number may also be determined from the identify message of the SCSI transfer. If the logical unit number is determined to be zero in step 606, then this indicates that the video data involved in the transfer includes a prepended header. This prepended header identifies the transfer and also indicates the MPEG channel number which is the destination of the transfer. Thus, once the SCSI controller 204 detects a LUN 0 transfer in step 606, in step 612 the controller 204 decodes the header for the function, e.g., a video data write, and the MPEG channel on which the data is to be transferred. If the SCSI controller 204 determines in step 606 that the logical unit number is not LUN 0, but rather is one of either LUN 1-6, then in step 614 the SCSI controller 204 uses the received LUN number as the MPEG channel associated with the transfer. Thus, if the LUN number in the command descriptor block is 1, then the SCSI control 204 interprets this as a video data transfer to be performed on MPEG channel 1. Similarly, if the LUN number is 2, then the MPEG channel on which the data is to be transferred is determined to be channel 2. Likewise, there is a one-to-one correspondence between LUNs 1-6 and MPEG channels 1-6 on a respective MPEG decoder box 122. Therefore, the present invention comprises a system and method for encoding the presence or absence of prepended header information, as well as a channel nwnber, on the logical unit number field in the command descriptor block of a SCSI transfer. This allows an MPEG decoder box 122 to operate with different file system formats, including file systems which either prepend header information or do not prepend header information. Although the system and method of the present invention has been described in connection with the described embodiments, it is not intended to be limited to the specific form set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the scope of the invention which is as defined by the appended claims.

Claims: A media server system, comprising: one or more decoder boxes (122), wherein each of said one or more decoder boxes includes a plurality of data channels; a computer system (102) including a memory media for storing data and a host adapter for coupling to a bus (112), characterized in that the computer system is configured to generate data transfers of blocks of data to individual ones of the one or more decoder boxes (122) through said bus (112), wherein the computer system (102) is configured to assign (508) a first value to a logical unit number to a field of a first of said data transfers targeting a first of the decoder boxes if a first block of data being transferred includes a header comprising channel information indicating a destination data channel from a plurality of data channels of the first decoder box, and wherein the computer system (102) is configured to assign (506) a value, corresponding to the destination data channel and different from said first value, to the logical unit number field of the first transfer if the first block of data being transferred does not include said header; wherein each of said one or more decoder boxes (122) is adapted to receive a block of the data from said computer system (102) in response to one of said data transfers targeting the decoder box and to transfer said received block of data on the destination data channel; and wherein each of said one or more decoder boxes (122) is configured to determine (604) the value contained in the logical unit number field of a transfer from the computer system, to determine (612) the destination data channel from the channel information in the header of the received block if the value contained in the logical unit number field is the first value, and to determine (614) the destination data channel from the value contained in the logical unit number field if the value contained in the logical unit number field is not the first value. The media server system of claim 1, wherein the computer system (102) is configured to selectively generate data transfers to each of said plurality of data channels in said one or more decoder boxes (122); wherein, in generating said first transfer of said first block of the data to the first decoder box, the computer system (102) is configured to encode said destination data channel to determine the value to be assigned to the logical unit number field if the first block of the data does not include said header. The media server system of claim 1, wherein said computer system comprises: means (504) for determining if the first block of the data being transferred in a data transfer includes a header comprising channel information; means (506) for assigning a value, corresponding to the destination data channel and different from the first value, to the logical unit number field of the data transfer if the first block of the data does not include said header. The media server system of claim 1, wherein each of the one or more decoder boxes (122) comprises: means for determining (604) a value contained in the logical unit number field of a data transfer from the computer system; determining (606,612) the destination data channel from the header in a received block of the data if the value contained in the logical unit number field of the data transfer is the first value; and means for determining (606,614) the destination data channel from the value contained in the logical unit number field of the transfer if the value contained in the logical unit number field is not the first value. The media server system of claim 1, wherein the computer system (102) is configurable to operate according to two or more different file systems; wherein the computer system is configured to include a header to a block of the data being transferred when said computer system is using a first file system architecture; and wherein the computer system is configured to not include a header to the block of the data being transferred when said computer system is using a second file system architecture. The media server system of claim 1, wherein said first value is zero. The media server system of claim 1, wherein the data transferred to the one or more decoder boxes (122) comprise multimedia data streams, wherein the multimedia data streams are MPEG compressed streams; and wherein each of said one or more decoder boxes (122) comprises a plurality of MPEG decoders corresponding to a plurality of data channels. The media server system of claim 1, wherein said bus (112) is a SCSI bus and wherein said host adapter is a SCSI host adapter. The media server system of claim 1, wherein the one or more decoder boxes (122) are coupled together in a daisy chain fashion. The media server system of claim 1, further comprising a cable (112) for connecting said computer system (102) to said one or more decoder boxes (122), wherein said cable realizes said bus. The media server system of claim 1, wherein each of the data channels of each of said one or more decoder boxes (122) is configured to decode a compressed MPEG stream. A method for transferring data in a media server system comprising a video server (102), one or more decoder boxes (122), each comprising a plurality of data channels, and a cable (112) connecting the video server to said one or more decoder boxes, the method being characterized by comprising: the video server reading (502) a first block of data from a storage media; the video server configuring said first block of the data for transfer to a selected one of the one or more decoder boxes (122), wherein said configuring includes assigning (508) a first value to a logical unit number field of the transfer if said first block of the data includes a header comprising channel information indicating a destination data channel from the plurality of data channels of the selected decoder box, and wherein said configuring includes assigning (506) a value, corresponding to the destination data channel and different from said first value, to the logical unit number field of the transfer if said block of the data does not include said header; the video server (102) performing said transfer of said first block of the data to said selected decoder box (122); said selected decoder box (122) receiving (602) said first block of data in response to said transfer; said selected decoder box (122) determining (604) value contained in the logical unit number field of said transfer; said selected decoder box determining (612) the destination data channel from the channel information in the header of the first block of the data if the value contained in the logical unit number is the first value; said selected decoder box determining (614) the destination data channel from the value contained in the logical unit number field if the value contained in the logical unit number field is different from the first value; said selected decoder box transferring the first block of the data on the destination data channel. The method of claim 12, wherein said configuring of the first block of the data for said transfer comprises encoding the destination data to determine the value to be assigned to the logical unit number field of the transfer if the first block of the data does not include said header. The method of claim 12, wherein the data transferred to the selected decoder box (122) comprises a multimedia data stream, wherein said multimedia data stream is an MPEG compressed stream; and wherein said transferring the first block of the data on the destination data channel comprises MPEG decoding said first block of the data. The method of claim 12, wherein the video server (102) is configurable to operate according to two or more different file systems; wherein said configuring said data for said transfer comprises including a header comprising channel information to the data being transferred when said video server is using a first file system; and wherein said configuring said data for said transfer comprises not including a header comprising channel information to the data being transferred when said video server is using a second file system. The method of claim 12, wherein said first value is zero. The method of claim 12, wherein each of the data channels of each of said one or more decoder boxes (122) is configured to decode a compressed MPEG stream.

Inventors: HOUGH JAMES K, HOUGH, JAMES K.
Applicants: SUN MICROSYSTEMS INC, SUN MICROSYSTEMS, INC.
Application year: 1997
Main classification: G06F17
IPC codes: H04N7