Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-07-06
2003-02-04
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C360S048000, C369S124010
Reexamination Certificate
active
06516136
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to decoding of data stored on a recording medium that is encoded with concatenated codes.
2. Description of the Related Art
Magnetic recording systems first encode user data into binary coded data bits that are subsequently recorded on a magnetic medium. Writing data to, and reading data from, the magnetic medium may be modeled as a transmission channel having an associated frequency response. A signal may then be read from the magnetic medium and sampled to provide a sequence of output samples containing the stored data. Magnetic recording systems for disk drives read and detect data from sectors of tracks on the magnetic medium (disk). Each track comprises user (“read”) data sectors as well as system dedicated control (e.g., “servo”) data sectors embedded between read sectors. Read data sectors store encoded user data that is read during read mode. Servo data sectors store servo data that is read during servo mode. Servo data is control data that the recording system uses during servo mode to 1) search for tracks (during sub- mode) and 2) position a read head over the track on the magnetic medium.
FIG. 1
shows a block diagram of a magnetic recording system
100
. A portion of the data stream is encoded with a predetermined code by data encoder
101
. The remaining, non-encoded portion of the data and the encoded portion of the data are further processed by the magnetic write head
102
and then recorded on the magnetic medium
110
by the magnetic write head
102
. Magnetic recording systems such as system
100
may employ one or more types of codes for data encoder
101
to map data bits to binary coded data bits. Such codes may be run-length limited (RLL) block codes, general convolutional codes, or 2T/bi-phase codes.
A magnetic read head
103
reads the information from the magnetic recording medium
110
as an analog signal. Magnetic write head
102
and magnetic read head
103
may be implemented as a single head read/write device. Magnetic read head
103
may provide a sampled analog signal representing the recorded user data and servo data as output channel samples. The term “output channel sample” refers to data that has passed through a transmission channel (e.g., magnetic medium
110
and magnetic read head
103
) that has a form of frequency response (possibly having memory). This type of transmission channel (possibly including the frequency response of a subsequent equalizer) may be termed a partial response channel. The signal containing the encoded data has an added noise component and added signal distortion caused by passing the signal through the channel's frequency response. To partially correct for variations in the channel's frequency response or for frequency response characteristics of the circuitry of magnetic read head
103
, the output channel samples may be applied to equalizer
104
. The equalized output channel samples are then applied to a soft output detector
105
, such as a partial-response, maximum-likelihood (PRML) detector. As shown in
FIG. 1
, soft output detector
105
is a PRML detector.
The exemplary PRML detector
105
employs an algorithm, such as the Viterbi algorithm (VA), to detect the sequence of symbol bits representing the encoded data from the equalized channel samples. An additional algorithm may be employed by a processor after the equalizer
104
to convert the equalized channel samples to a sequence soft output samples. Data decoder
106
receives the sequence of soft output samples from the soft output detector
105
and decodes the sequence to reconstruct the data.
For an exemplary magnetic recording system
100
, one sector of data recorded on the medium comprises 512 bytes (4096 bits). After data in one section is processed, the operation of the servo mode changes the position of the magnetic read head
103
. During the servo mode operation, the read mode operation is suspended until the servo mode operation is complete. Each of the servo and read mode operations requires a corresponding decoding operation.
Concatenated code systems for encoding and decoding data use two or more component codes that are concatenated during the process of encoding data. Although the codes may be of any type, component codes are typically relatively simple codes, such as the rate 8/9 convolutional code. The two or more component codes are concatenated in either a serial concatenation or a parallel concatenation. In both methods of concatenation, an interleaver may be inserted between the encoders for the component codes. For example, in the serial concatenation of two component codes, data is encoded by a first encoding module with a first component code. This encoded data is, in turn, passed through an interleaver and then applied to a second encoding module for encoding with a second component code. This process operates on only a single, serial data stream, and the first and second component codes may be the same code. In the parallel concatenation, data is encoded with the first component code and also the interleaved data is encoded with a second component code. The two encoded streams are combined in parallel to provide a single encoded data stream, for example, by multiplexing.
Concatenated code systems may employ iterative decoding of encoded data using either serial or parallel iterative decoding methods. Each of the serial or parallel iterative decoding methods may be employed for serial concatenated codes. Each of the serial or parallel iterative decoding methods may be employed for parallel concatenated codes. When employing iterative decoding of data encoded with a concatenated code, a block of data is input to the iterative decoder. The block boundaries desirably conform to symbol boundaries of the concatenated code. The iterative decoder comprises at least one decoding module having N component code decoders for decoding N component codes. Each decoding module and/or component code decoder may typically include a maximum a posteriori, (MAP) decoder. The particular implementation of the decoding module is dependent on which method of serial or parallel concatenation is used by the concatenated code.
In an iterative decoding method, a block of the soft output samples representing encoded data is repetitively processed for decoding by the two or more decoding modules until a predetermined number (I) of decoding iterations are complete. An exemplary iterative decoder
200
employing serial iterative decoding is shown in FIG.
2
. Each decoding module
201
-
203
performs a complete, “soft” decoding of the data encoded with a concatenated code. Each decoding module applies an iteration of the decoding process, and each iteration allows for higher confidence in the decisions for bits in the output decoded data that are made based on the output samples of a detector, such as the PRML detector
105
. Each decoding module includes N component code decoders
210
-
212
(i.e., Decoder
1
through Decoder N). Each component code decoder corresponds to one of the N component codes employed by the concatenated code. Each of the component code decoders
210
-
212
may include, for example, a MAP decoder and a deinterleaver.
For the implementation of serial iterative decoding shown in
FIG. 2
, I iterations of the decoding operations are performed on each packet. A new block is applied to the first decoding module
201
as the previous packet is applied to the second decoding operation of decoding module
202
. The second decoding operation of decoding module
202
corresponds to the second decoding iteration. A fully decoded block is provided as data from the Ith decoding module
203
, corresponding to the Ith decoding iteration. Once all decoding modules
201
-
203
of iterative decoder
200
are loaded with data, the decoding process may occur in a pipeline fashion and/or continuously as each new block is applied.
To avoid a repeated implementation of the two or more decoding modules in the serial iterative decoding such as shown in
FIG. 2
Agere Systems Inc.
Hughes Ian M.
Mendelsohn Steve
Tran Thai
LandOfFree
Iterative decoding of concatenated codes for recording systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Iterative decoding of concatenated codes for recording systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Iterative decoding of concatenated codes for recording systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3156719