External memory for PVR

一种用于个人录像机或电视机顶盒的外部存储装置。MPEG传输流会进行过滤(212)以去除与选定节目不相关的信息。此过滤的传输流会被加密(216)，然后作为同步数据通过IEEE 1394总线(126)传送到外部存储装置(120)。外部存储装置(120)将过滤的传输流解密(220)，并将PAT和PMT表送回个人录像机。那些表在编辑后可去除与选定节目不相关的信息，然后送回外部存储装置(120)以重新插入传输流，从而产生修改后的传输流。此修改后的传输流会存储在外部硬盘驱动器(234)上。修改后的传输流可在存储于硬盘(234)之前或之后进行加密。如果在系统头端对选定的节目进行加扰，则在使用ECM中所含并与MPEG传输流上的节目一起发送的密钥过滤前，在PVR(或STB)中对节目进行解扰。 An external storage device for a personal video recorder or television Set-Top Box. An MPEG transport stream is filtered to remove information not relevant to a selected program. This filtered transport stream is encrypted and then transmitted as isochronous data over an IEEE 1394 bus to an external storage device. The external storage device decrypts the filtered transport stream and returns PAT and PMT tables to the personal video recorder. Those tables are edited to remove information not relevant to the selected program and returned to the external storage device for reinsertion into the transport stream to produce a modified transport stream. This modified transport stream is stored on the external hard disc drive. The modified transport stream may be encrypted prior to or after storage on the hard disc drive. If the selected program is scrambled at the system head end, the program is descrambled in the PVR (or STB) before the filtering using a key which is contained in the ECM and delivered with the program on the MPEG Transport Stream.