Abstract: Data storage techniques particularly well-suited for use in archival data storage are disclosed. In one aspect of the invention, a data block is processed to generate an address as a function of the contents of the data block, and the data block is then stored in the system in a memory location identified by the address. The processing operation is configured to provide write-once archival storage of the data block, in that the contents of the data block are not modifiable without also altering the address of the data block determinable in the processing operation. In an illustrative embodiment, the processing of the data block involves determining a substantially unique identifier of the data block by applying a collision-resistant hash function to the contents of the data block, and the address is subsequently determined from the substantially unique identifier by utilizing the identifier to perform a lookup of the address in an index.

Abstract: Data storage techniques particularly well-suited for use in archival data storage are disclosed. In one aspect of the invention, a data block is processed to generate an address as a function of the contents of the data block, and the data block is then stored in the system in a memory location identified by the address. The processing operation is configured to provide write-once archival storage of the data block, in that the contents of the data block are not modifiable without also altering the address of the data block determinable in the processing operation. In an illustrative embodiment, the processing of the data block involves determining a substantially unique identifier of the data block by applying a collision-resistant hash function to the contents of the data block, and the address is subsequently determined from the substantially unique identifier by utilizing the identifier to perform a lookup of the address in an index.

Abstract: A method and apparatus for compressing packets that enables inter-packet compression thereby achieving greater robustness and increased compression ratios without the deleterious effects, e.g., the effect of packet loss multiplying, of prior compression schemes. More particularly, a so-called acknowledgment scheme is employed in conjunction with the specific compression algorithm such that the transmitter, i.e., sender, can limit the history used by the compression algorithm to those packets that are correctly received. In particular, a vector identifying the packets used as the history is included in the compressed packet thereby enabling the receiver to reconstruct the packet history state necessary to decompress the packet. Advantageously, increased robustness and greater compression ratios are achieved independent of any particular one compression scheme.

Abstract: A method and apparatus for compressing packets that enables inter-packet compression thereby achieving greater robustness and increased compression ratios. More particularly, a variable-length coding is used in conjunction with maintaining a separate hash table for each packet. Further, the per-packet hash table indexes particular byte strings in the packet but does not index data in any other packet(s). That is, a respective separate hash table for each packet is employed wherein such hash table is constructed as the particular packet is compressed. As such, the respective hash table is encoded with the particular packet. Employing a per-packet hash table in combination with variable history state inter-packet compression provides for efficient and robust overall compression of the packets.

Abstract: An independent transport layer is used as an error correction mechanism in a method employing perceptual audio coding. The transport layer is characterized by the addition of information, via a transport header, to each of a succession of blocks of encoded program material which is independent of the information within its respective block of encoded program material. The transport header comprises information on the structure of the block. Thus, the transport header is easily separated from the digital representation of the program material and is independent of the content of the digital representation thereby providing for changing of the content of the digital representation without changing the transport layer.

Abstract: A method of encoding an audio signal is disclosed. The method comprises partitioning the audio signal into a first time block and a second time block. Next, a first time block first energy value and a first time block second energy value are calculated. Next, a second time block first energy value and a second time block second energy value are calculated. Next, the technique determines if an attack has occurred in the second time block by comparing the second time block first energy value and the second time block second energy value and also comparing the Erst time block and the second time block Advantageously, the method identifies attach such that the decoder can reproduce the attacks with little audible distortion and also affords the advantage of using long windows for portions of the audio signal that do not contain attacks.

Abstract: A new technique for the determination of the masking effect of an audio signal is employed to provide transparent compression of an audio signal at greatly reduced bit rates. The new technique employs the results of recent research into the psycho-physics of noise masking in the human auditory system. This research suggests that noise masking is a function of the uncertainty in loudness as perceived by the brain. Measures of loudness uncertainty are employed to form noise masking thresholds for use in the compression of audio signals. These measures are employed in an illustrative subband, analysis-by-synthesis framework. In accordance with the illustrative embodiment, provisional encodings of the audio signal are performed to determine the encoding which achieves a loudness differential, between the original and coded audio signal, which is less than (but not too far below) the loudness uncertainty.