Abstract: A method and apparatus is disclosed which minimizes the visual artifacts normally generated when images are compressed for transfer through very narrow band channels such as, for example, the Internet. To this end, the images are pre-filtered and then scaled down prior to compression using a two dimensional spatial impulse filter with good pulse fidelity rather than flat pass bands, rapid cutoff at high frequency and minimal impulse response width. The impulse filter preferably is operated at the 6 db point down about 0.6 to 0.9 of the output image spatial band edge, thereby removing visible aliases in the images while compromising between subjective sharpness and total picture entropy.

Abstract: A read/write magnetic head includes a step offset formed in the gap of the head which accordingly generates recorded transitions in a recording medium which also contain a step offset in each successively recorded transition along the length of a track. On subsequent playback of the track by the same or similar step gap head, fine transverse mistracking of the head as it follows the track results in a corresponding echo signal being generated along with the main readout signal. The amplitude of the echo signal is indicative of the degree of fine mistracking while the location of the echo signal relative to the main signal is indicative of the direction of mistracking. Fine mistracking correction is provided by circuits which detect the amount and direction of mistracking and supply an error signal to a tracking servo to correct the mistracking.

Abstract: A servomechanism for controlling the position of a magnetic-tape playback head (16) with respect to a track (24) of digital data on a magnetic tape (22) positions the head by reference to an error signal that error-signal-generation circuitry (FIG. 10). generates. Sample-clock signals obtained from simultaneously read azimuth-recorded data tracks clock respective frequency dividers (52 and 54), and a phase detector 56 generates the error signal by comparing the frequency dividers' outputs.

Abstract: An improved, shielded magnetic core structure is disclosed that is particularly well suited for use in magnetic read and write heads adapted for narrow track, short wavelength magnetic recording systems, and for transformers of high performance, wide band application. The improved magnetic cores use novel field confinement structures to reduce or eliminate leakage magnetic paths which normally do not link the head gap or do not link the transformer windings. This shielding arrangement substantially improves the performance of such devices, as compared to conventional, unshielded heads and transformers. Embodiments involving toroidal cores, thin film heads, and MR heads are disclosed, along with high performance, wide band transformer structures.

Abstract: In an azimuth recording format, the crosstalk of the A channel into the B channel is higher than the crosstalk of the B channel into the A channel because, at the ends of a magnetic recording where the switching contour of constant magnetic field strength is equal to the media magnetization switching field, the switching contour follows a curve. The resulting curvature at the ends of the magnetic recording vary accordingly the angle of azimuth rejection between the B to A azimuth relative to the A to B azimuth at the edges of the track. The use of a record head of a unique design wherein the trailing pole face of the head extends laterally beyond its leading pole face at the over-writing side of the head, removes the curvature at the ends of the transition recordings forming the recorded tracks.

Abstract: A transition overshoot of the record current is usual to compensate record head efficiency loss at high frequencies. Recording compatibility is achieved by decreasing the record current overshoot at the digital data signal transitions as the head gap depth decreases due to wear. Additionally, the different gap depth record heads of different head efficiencies require different optimum record current levels to provide maximum signal-to-noise ratio in the reproduced signal. The head gap depth thus is monitored by means of the optimum record current level without actually measuring the gap depth. The desired amount of overshoot is adaptively adjusted to the gap depth during the recording process by tracking the overshoot to the optimum record current level derived by adjusting the record drive level signal. Recording compatibility between different gap depth heads is achieved using the existing normal record current optimization process during recording.

Abstract: A magnetic transducer for reproducing/recording high frequency signals with a magnetic tape medium includes a pair of opposed transducer head halves separated by an insulation gap and bonded together to form a Y-shaped pole structure, each half including a laminated at least partially ferromagnetic core portion bounded on opposite surfaces with outer and inner conductive layers, each of which forms a winding coil portion. Each core section has a leg portion and an angularly disposed arm portion, the distal end of which is capped with a block-shaped ferromagnetic pole tip in magnetic path relation therewith, the two pole tips lying in a common plane transverse to the plane of the gap. The conductive layers, when conductively interconnected, such as by jumpers, form a one or two turn coil for the transducer.

Abstract: Input data symbols are written to a synchronization (sync) adder, which appends a pseudo randomly (PN) generated sync bit to generate a sync word. Sync words are sent to a receiver where synchronization is recovered. The receiver re-generates the same PN sequence that was generated at the transmitter. Synchronization recovery apparatus conceptually looks at each bit position to locate the appended PN sequence. When the sync bit position is found, the data stream is assembled into fixed length sync words and the data symbols of the sync words are written into a buffer at an address determined by the position of the sync bit in the PN sequence. Error rates in the data stream of sync words are measurable using a correlator network for reading the bit in the sync bit position of a sync word and for comparing that bit with its expected value in a reconstructed PN sequence to provide a difference value where the difference is a measure of the error rate in the data stream.

Abstract: Input data symbols are written in a write buffer then to a sync adder, which appends a pseudo randomly (PN) generated sync bit to the MSB position of a four-symbol sync word data field, to generate a sync word. Sync words may or may not be randomized and sent to a receiver whereafter synchronization is recovered and perhaps de-randomized symbols are written into particular positions of an ECC block in a read buffer which are derivable from the PN sequence. The ECC block is a data array having multi-bit sync words making up its rows and the bit positions of the sync words making up its columns. Synchronization recovery apparatus conceptually looks at each bit position across a row and in a top-to-bottom direction down each of the columns to locate that column which contains the appended PN sequence. Sync recovery involves the receiver re-generating the same PN sequence that was generated at the transmitter.

Abstract: A magnetic transducer for reproducing/recording high frequency signals with a magnetic tape medium includes a pair of opposed transducer head halves separated by an insulation gap and bonded together to form a Y-shaped pole structure, each half including a laminated at least partially ferromagnetic core portion bounded on opposite surfaces with conductive layers, each of which forms a winding coil portion. Each core section is formed as one-half of a Y-shaped cross-sectional configuration having a leg portion and an angularly disposed arm portion, the distal end of which is capped with a block-shaped ferromagnetic pole tip in magnetic path relation therewith, the two pole tips lying in a common plane transverse to the plane of the gap. The conductive layers on the outer and inner surfaces of the laminated core section form outer and inner conductors which, when conductively interconnected, such as by jumpers, are configured to form a one or two turn coil for the transducer.