Digital Camera Patent Abstract
The present invention provides a method (200, 400, 500, 600), device
(300, 400, 500, 600, 700) and digital camera (800) for error control
of a wavelet-based image codec, wherein wavelet coefficients are
encoded using entropy coding. The method includes: A) utilizing,
in a decoder, control information and a plurality of resynchronization
markers inserted at arbitrary positions in a wavelet-based image
bitstream wherein the control information provides decoding information
for decoding at least a forward sequence of wavelet coefficients;
and B) detecting errors in an image bitstream and limiting propagation
of errors in a decoded image utilizing the control information and
the plurality of resynchronization markers. Digital Camera Patent Claims
We claim:
1. A method of error control of a wavelet-based image codec, wherein
wavelet coefficients are encoded using entropy coding, comprising
the steps of:
A) utilizing, in a decoder, control information and a plurality
of resynchronization markers inserted at arbitrary positions in
a wavelet-based image bitstream wherein the control information
provides decoding information for decoding at least a forward sequence
of wavelet coefficients;
B) detecting errors in an image bitstream and limiting propagation
of errors in a decoded image utilizing the control information and
the plurality of resynchronization markers,
wherein the control information includes an absolute restart address
in a predetermined wavelet-based image decomposition scheme, and
wherein the absolute restart address includes at least one of:
C) an absolute subband address in a predetermined wavelet decomposition
scheme;
D) an absolute spatial position address in a predetermined wavelet
subband coefficient-scanning scheme;
E) an absolute class address in a predetermined wavelet coefficient
classification scheme; and
F) an absolute coefficient accuracy value in a predetermined variable
coefficient accuracy wavelet-coding scheme.
2. The method of claim 1 wherein the control information includes
decoding information for decoding a backward sequence of wavelet
coefficients utilizing reversible entropy codewords.
3. The method of claim 1 wherein the control information includes
a resetting of predetermined predictively encoded information at
a boundary of bitstream segments.
4. The method of claim 1 wherein the absolute class address in
the predetermined wavelet coefficient classification scheme includes
classification according to at least one of:
A) classes of individual wavelet coefficients;
B) classes of blocks of wavelet coefficients; and
C) classes of multiresolution trees of wavelet coefficients.
5. The method of claim 1 wherein detecting an error in the image
bitstream includes detecting an error in the absolute restart address
including at least one of:
A) detecting loss of entropy coding synchronization;
B) detecting an incorrect absolute subband address;
C) detecting an incorrect absolute spatial position address;
D) detecting an incorrect absolute class address; and
E) detecting an incorrect absolute coefficient accuracy value are
present.
6. The method of claim 1 wherein the method is a process whose
steps are embodied in at least one of:
A) an application specific integrated circuit;
B) a field programmable gate array; and
C) a microprocessor; and
D) a computer-readable memory;
arranged and configured to decode a wavelet-based image bitstream
in accordance with the scheme of claim 1.
7. A method of region of interest localization of a wavelet-based
image codec, wherein wavelet coefficients are encoded using entropy
coding, comprising the steps of:
A) localizing, in a decoder, wavelet coefficients associated with
one or more predetermined regions of interest utilizing control
information and a plurality of resynchronization markers wherein
the control information provides information for decoding at least
one region of interest in an image;
B) detecting boundaries of regions of interest in an image bitstream
and limiting the decoding of the image bitstream to at least one
region of interest utilizing the plurality of resynchronization
markers and the control information;
wherein the control information includes an absolute restart address
in a predetermined wavelet-based image decomposition scheme and
wherein the absolute restart address includes at least one of:
C) an absolute subband address in a predetermined wavelet decomposition
scheme;
D) an absolute spatial position address in a predetermined wavelet
subband coefficient-scanning scheme;
E) an absolute class address in a predetermined wavelet coefficient
region of interest classification scheme; and
F) an absolute coefficient accuracy value in a predetermined variable
coefficient accuracy wavelet-coding scheme.
8. The method of claim 7 wherein the control information includes
a resetting of predetermined predictively encoded information at
a boundary of bitstream segments.
9. The method of claim 7 wherein the absolute class address in
the predetermined wavelet coefficient region of interest classification
scheme includes classification according to at least one of:
A) classes of individual wavelet coefficients of a region of interest;
B) classes of blocks of wavelet coefficients of a region of interest;
and
C) classes of multiresolution trees of wavelet coefficients of
a region of interest.
10. The method of claim 7 wherein the method is a process whose
steps are embodied in at least one of:
A) an application specific integrated circuit;
B) a field programmable gate array; and
C) a microprocessor; and
D) a computer-readable memory;
arranged and configured to decode one or more regions of interest
of a wavelet-based image bitstream in accordance with the scheme
of claim 8.
11. A device for error control of a wavelet-based image codec,
wherein wavelet coefficients are encoded using entropy coding, wherein
the device is directed by a computer program that is embodied in
at least one of A-D:
A) a memory;
B) an application specific integrated circuit;
C) digital signal processor; and
D) a field programmable gate array, and the computer program includes
the steps of:
E) utilizing control information and a plurality of resynchronization
markers inserted at arbitrary positions in a wavelet-based image
bitstream wherein the control information provides decoding information
for decoding at least a forward sequence of wavelet coefficients;
F) detecting errors in an image bitstream and limiting the propagation
of errors in a decoded image utilizing the control information and
the plurality of resynchronization markers
wherein the control information includes an absolute restart address
in a predetermined wavelet-based image decomposition scheme, and
wherein the absolute restart address includes at least one of:
G) an absolute subband address in a predetermined wavelet decomposition
scheme;
H) an absolute spatial position address in a predetermined wavelet
subband coefficient-scanning scheme;
I) an absolute class address in a predetermined wavelet coefficient
classification scheme; and
J) an absolute coefficient accuracy value in a predetermined variable
coefficient accuracy wavelet-coding scheme.
12. The device of claim 11 wherein the control information computed
by a resynchronization controller defines a boundary of segments
of wavelet coefficients.
13. The device of claim 11 wherein the absolute class address in
the predetermined wavelet coefficient classification scheme includes
classification according to at least one of:
A) classes of individual wavelet coefficients;
B) classes of blocks of wavelet coefficients; and
C) classes of multiresolution trees of wavelet coefficients.
14. The device of claim 11 wherein, in the steps implemented by
the computer program, detecting an error in the image bitstream
includes detecting an error in the absolute restart address including
at least one of:
A) detecting loss of entropy coding synchronization;
B) detecting an incorrect absolute subband address;
C) detecting an incorrect absolute spatial position address;
D) detecting an incorrect absolute class address; and
E) detecting an incorrect absolute coefficient accuracy value are
present.
15. A device for region of interest localization of a wavelet-based
image codec, wherein wavelet coefficients are encoded using entropy
coding, comprising:
A) a decoder, having a wavelet coefficient localizer for localizing
wavelet coefficients associated with one or more predetermined regions
of interest utilizing control information and a plurality of resynchronization
markers wherein the control information provides information for
decoding at least one region of interest in an image; and
B) a boundary detector, coupled to the decoder, for detecting boundaries
of regions of interest in an image bitstream and limiting the decoding
of the image bitstream to one or more regions of interest utilizing
the plurality of resynchronization markers and control information
wherein the control information includes an absolute restart address
in a predetermined wavelet-based image decomposition scheme, and
wherein the absolute restart address includes at least one of:
C) an absolute subband address in a predetermined wavelet decomposition
scheme;
D) an absolute spatial position address in a predetermined wavelet
subband coefficient-scanning scheme;
E) an absolute class address in a predetermined wavelet coefficient
region of interest classification scheme; and
F) an absolute coefficient accuracy value in a predetermined variable
coefficient accuracy wavelet-coding scheme.
16. The device of claim 15 wherein the control information defines
a resetting of predetermined predictively encoded information at
a boundary of bitstream segments.
17. The device of claim 13 wherein the absolute class address in
the predetermined wavelet coefficient region of interest classification
scheme includes classification according to at least one of:
A) classes of individual wavelet coefficients of a region of interest;
B) classes of blocks of wavelet coefficients of a region of interest;
and
C) classes of multiresolution trees of wavelet coefficients of
a region of interest.
18. A digital camera having a device for region of interest localization
of a wavelet-based image codec, wherein wavelet coefficients are
encoded using entropy coding, wherein the device comprises:
A) a decoder having a wavelet coefficient localizer, for localizing
wavelet coefficients associated with one or more predetermined regions
of interest utilizing control information and a plurality of resynchronization
markers wherein the control information provides information for
decoding at least one region of interest in an image; and
B) a boundary detector, coupled to the decoder, for detecting boundaries
of regions of interest in an image bitstream and limiting the decoding
of the image bitstream to one or more regions of interest utilizing
the plurality of resynchronization markers and control information.
wherein the control information includes an absolute restart address
in a predetermined wavelet-based image decomposition scheme, and
wherein the absolute restart address includes at least one of:
C) an absolute subband address in a predetermined wavelet decomposition
scheme;
D) an absolute spatial position address in a predetermined wavelet
subband coefficient-scanning scheme;
E) an absolute class address in a predetermined wavelet coefficient
region of interest classification scheme; and
F) an absolute coefficient accuracy value in a predetermined variable
coefficient accuracy wavelet-coding scheme.
19. The digital camera of claim 18 wherein the control information
includes a resetting of predetermined predictively encoded information
at a boundary of bitstream segments.
20. The digital camera of claim 18 wherein the absolute class address
in the predetermined wavelet coefficient region of interest classification
scheme includes classification according to at least one of:
A) classes of individual wavelet coefficients of a region of interest;
B) classes of blocks of wavelet coefficients of a region of interest;
and
C) classes of multiresolution trees of wavelet coefficients of
a region of interest.
Digital Camera Patent Description
FIELD OF THE INVENTION
This invention relates to the encoding and decoding of compressed
image bitstreams in the presence of error prone channels. More particularly,
this invention pertains to compressed image bitstreams generated
using the discrete wavelet transform and its variants.
BACKGROUND OF THE INVENTION
The transmission of compressed images over noisy or error prone
channels is a difficult problem, but one which is very relevant
to a number of systems in use today. Errors may be injected into
a transmitted bitstream in both wired and wireless environments.
In the case of wired networks, there are a variety of unreliable
transmission protocols which may result in lost packets of information
at a decoder due to network congestion. Mobile wireless networks
often exhibit Rayleigh fading or burst errors as a result of multipath
propagation. These examples are relevant to the transmission of
image data because a wide variety of multimedia applications have
recently come into existence which require the delivery of image
data over such error prone networks. Transmitting image data over
the Internet using the User Datagram Protocol (UDP) is one example
application which may result in erroneous data at the decoder in
the presence of network congestion.
Currently, as is known in the art, the most popular standard for
image compression for use in network based multimedia is JPEG (a
standardized image compression mechanism developed by the Joint
Photographic Experts Group). The JPEG standard is a block based
Discrete Cosine Transform (DCT) standard, which transmits the spatial
information in a frame in several different ways. The most common
use of JPEG is in its baseline form, where the image data appears
sequentially in blocks in raster scan order in the bitstream. When
a baseline JPEG bitstream is subjected to errors, large spatial
portions of the image will be lost. JPEG permits structuring entropy
coded data into segments, so it is possible to recover other segments
of an image, when errors are localized to a segment.
Another form of JPEG is the progressive mode. In this mode, image
data appears not only sequentially in blocks in raster scan order,
but also in scans of increasing frequency resolution and/or DCT
coefficient accuracy. This mode allows for data to appear in low
quality form first at a decoder, and then be decoded and displayed
while higher resolution information is still being transmitted.
Like the baseline mode, when a progressive JPEG bitstream is subjected
to errors, the errors must be localized to predetermined segments
in order to contain the propagation of errors to different spatial
regions of the image, or to different resolution scans of the image.
The idea of progressive or scalable transmission of image data
is a useful one, when considering the effects of errors on the bitstream.
While the progressive mode of JPEG provides a piece-wise approximation
of "scalability", it does not provide the flexibility
that the wavelet transform does in the form of continuously scalable
bitstreams. Such bitstreams are ones that may be decoded up to an
arbitrary position in the bitstream, where the decoded image is
always increasing in quality with subsequent decoded bits. When
the data is transmitted in n inherently prioritized fashion, as
is enabled by the wavelet transform, it is much easier to obtain
useable images in the presence of errors. This is because any data
appearing after an error may easily be concealed, or left undecoded,
and an image will still appear to look like the expected image.
One problem with the existing wavelet based image compression algorithms,
however, is that the algorithms are not explicitly designed to be
used in the presence of errors. Therefore, although the data may
be partitioned in an error resilient manner, the decoder may not
be able to localize and conceal the errors without new and enabling
technology.
When errors are present in a compressed image bitstream, some means
must exist for an image decoder to detect those errors, and to react
accordingly in order to localize and conceal those errors before
displaying the image. In a system where some residual errors are
found at the application layer, it is crucial that the application
(in this case a wavelet based image decoder) have the ability to
control the effects of those errors.
The concept or detecting and localizing errors is coupled to the
problem of detecting and decoding regions of interest in an image.
An encoder may need to apply some specific rate control algorithms
to an image such that an unequal amount of bits are spent on certain
regions of interest in the image. If a decoder is to selectively
decode those regions of interest based on demands of certain applications,
that selective decoding must be enabled by technology which has
the same properties that an error control localization method would
have. Those properties would include the ability to detect the boundaries
of regions of interest, and continue decoding in a forward direction
based on special information found at those boundaries. Such technology
does not exist in wavelet based image codecs today.
Thus, there is a need for a method and device for error control
and region of interest localization of a wavelet based image compression
system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic representation of the location of error
control and region of interest localization information in accordance
with the present invention.
FIG. 2 is a flow chart of a preferred embodiment of steps of a
method in accordance with the present invention.
FIG. 3 is a block diagram of one preferred embodiment of a device
in accordance with the present invention.
FIG. 4 is a flow chart showing another embodiment of a method in
accordance with the present invention.
FIG. 5 is a flow chart showing another embodiment of steps of a
method in accordance with the present invention.
FIG. 6 is a block diagram showing a device directed by a computer
program that is embodied in at least one of: a memory, an application
specific integrated circuit; a digital signal processor; microprocessor
and a field programmable gate array in accordance with the present
invention.
FIG. 7 is a block diagram of one embodiment of a device for region
of interest localization of a wavelet-based image codec in accordance
with the present invention, wherein wavelet coefficients are encoded
using entropy coding.
FIG. 8 is a block diagram showing a digital camera that includes
the device for region of interest localization of a wavelet-based
image codec, wherein wavelet coefficients are encoded using entropy
coding, in accordance with the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The present invention provides a method and device for the reliable
error control and region of interest localization of wavelet based
compressed image data for use with systems containing an error prone
channel. The method is designed to work with any image compression
system that generates wavelet based subbands, including, but not
limited to, dyadic multiresolution discrete wavelet transforms and
arbitrary wavelet packet decompositions. The method is characterized
by the following capabilities:
1. Provides both random and burst error protection.
2. Provides a means for detecting errors in a wavelet encoded image
bitstream.
3. Limits the propagation of errors within the decoded image.
4. Provides a means to apply error concealment to an error corrupted
wavelet encoded image.
5. Provides a means to decode only a region or regions of interest
in a wavelet encoded image.
This method provides a format for transmitting segments of wavelet
coded image data in an error prone environment. The boundaries of
segments of wavelet coded data are signaled by resynchronization
markers in the bitstream, followed by special control information
to enable the continued decoding of the image in the presence of
errors. One problem with compressed image data is that entropy codes
such as variable length Huffman codes, or arithmetic codes, are
not robust to errors. Such codes are typically used in wavelet-based
image coding systems to provide very good compression. The problem
of making these codes resilient to errors is one that is pervasive
in the world of wireless and error prone communications. Errors
in variable length and arithmetic codes propagate until being reset
in some manner. Therefore the compression technique must provide
for this option if it is to be error resilient.
With wavelet coded image data, it is beneficial to be able to localize
the regions of the bitstream in which errors occur, and then conceal
those errors using simple coefficient replacement techniques. One
example would be to localize errors to a single subband of wavelet
coefficients, and then to set all of the coefficients in that subband
to zero before applying the inverse wavelet transform. The unique
property of wavelet transforms is that the decoded data will still
look like the encoded image even in the presence of such concealment.
This is a result of the multiresolution prioritization of data that
is inherent to wavelet decompositions.
A diagrammatic representation of a wavelet decomposition and several
associated error control segmentations of the present invention
is shown in FIG. 1, numeral 100. FIG. 1 indicates graphically the
location of resynchronization information relative to different
bitstream orderings of wavelet coefficients. The diagrams show the
dyadic wavelet decomposition tree of an image, which is coded and
transmitted in the bitstream here in order of lowest resolution
to highest resolution coefficients. FIG. 1, (102), shows the placement
of resynchronization markers and control information at the boundaries
of each subband in a wavelet decomposition. in the case of such
a segmentation, all of the data in each subband could
be decoded independently of all other subbands' data. Here, the
resynchronization markers and control information contain all of
the necessary information to continue decoding, such as the absolute
address of the current subband, and the resetting of any predictive
coding techniques which might cross a subband border. In another
case, the data appears in the bitstream in terms of accuracy, or
bitplanes (104). Here resynchronization markers and control information
can be placed at the boundary of every bitplane in every subband.
In this case, it is possible to recover more significant bitplanes
in the presence of errors, and utilize that data in the inverse
transform, while localizing and concealing erroneous bitplanes at
a finer level of accuracy. Finally, FIG. 1, (106) shows the use
of resynchronization markers and control information for the segmentation
of classes, or regions of interest, of wavelet coefficients. In
(106) one important class, Class 0, is shown. The coefficients associated
with this class may form a specific region of interest in the image.
With adequate resynchronization and control information, it is possible
to localize the decoding with or without errors to the coefficients
associated with a specific class (which may be a region of interest).
The coefficients in a class need not appear in a contiguous group
within the image, as shown here, but could be dispersed throughout
the image and contiguously decoded. Both cases require a class map
is provided to a decoder in an image header.
FIG. 2, numeral 200, is a flow diagram of one preferred embodiment
of a method in accordance with the present invention. FIG. 2 shows
the placement of resynchronization markers (202) and control information
(204) in a wavelet-based compressed image bitstream. The placement
is controlled by a predetermined user defined scheme in accordance
with one or a combination of the approaches described above and
represented in FIG. 1, (100). The resynchronization markers in this
embodiment are unique codewords in a wavelet coded bitstream, which
are not emulated in the entropy coded symbols used to represent
quantized wavelet coefficients in the compressed bitstream. Each
resynchronization marker is followed by a control information field
of a predetermined number of bits, F, in length. The length of the
control field is a function of the current subband, and of the predetermined
user defined scheme for coding the wavelet coefficients. The components
of the control length field are at least one of:
A) an absolute subband address in a predetermined wavelet decomposition
scheme (A bits) (206);
B) an absolute spatial position address in a predetermined wavelet
subband coefficient scanning scheme (B bits) (208);
C) an absolute class address in a predetermined wavelet coefficient
classification scheme (C bits) (210); and
D) an absolute coefficient accuracy value in a predetermined variable
coefficient accuracy wavelet coding scheme (D bits) (212).
Thus, the total length of the control information field is (A+B+C+D)
bits. In a predetermined wavelet decomposition scheme where the
maximum number of wavelet subbands is N.sub.A, A=Ceil(log.sub.2
(N.sub.A)) bits, where Ceil() is the round-up-to-nearest-integer
function. In a predetermined wavelet decomposition scheme where
the number of wavelet coefficients in the current subband is N.sub.B,
B=Ceil(log.sub.2 (N.sub.B)) bits. In a predetermined wavelet decomposition
scheme where the number of classes of wavelet coefficients is N.sub.C,
C=Ceil(log.sub.2 (N.sub.C)) bits. In a predetermined wavelet decomposition
scheme where the number of classes of wavelet coefficients is N.sub.D,
D=Ceil(log.sub.2 (N.sub.D)) bits. For example, in a wavelet decomposition
having 10 subbands, and 65536 coefficients in the current subband,
and 4 classes and 32 bitplanes of accuracy, F=(A+B+C+D)=(4+16+2+5)=27
bits.
The content of the control field in this embodiment provides a
bitstream decoder the means to detect errors in a bitstream (214).
This error detection property comes about as a result of the fact
that data always appears in a wavelet-based image bitstream in a
predetermined order, as governed by the bitstream syntax known to
the decoder. This syntax provides a picture header which informs
the decoder about the current configuration of any adjustable syntax
parameters for the current bitstream. When a bitstream is corrupted
by an error, such as a burst or packet loss error, the erroneous
data may hinder the ability of a decoder to know its relative location
to the start of the image. The control fields, which may be accurately
decoded when a unique resynchronization marker is found, tell the
decoder what the current bitstream position should be. If the decoder's
internal record of the current subband, spatial address, class,
or accuracy value does not match the control field data, an error
may be detected. This functionality is crucial to bitstreams which
are highly compressed by concatenating long series of variable length
codewords or arithmetically encoded codewords together.
Once an error has been detected, the decoder is then enabled to
localize (216) the error to a region between the last decoded resynchronization
marker and the current resynchronization marker. For the purposes
of localization, the start of the image file acts as the first resynchronization
marker. If the encoded bitstream contains reversible variable length
codewords, the codewords may be read in a reverse direction from
the point of the current resynchronization marker, thus recovering
data (218) and localizing the errors to a smaller number of bits.
The localized region of error may then be concealed using an error
concealment method (220) such as setting all coefficients in the
localized error region to zero.
FIG. 3, numeral 300, is a block diagram of one preferred embodiment
of a device in accordance with the present invention. The device
is used for error control of a wavelet-based image codec, wherein
wavelet coefficients are encoded using entropy coding. The device
includes a bitstream controller (302) coupled to receive the compressed
wavelet-based image bitstream (301). The bitstream controller is
directed by an external parameter controller (304) incorporating
predetermined wavelet decomposition parameters (305). The bitstream
controller inserts resynchronization markers (306) and control information
fields with an absolute restart address including at least one of
an absolute subband address (308); an absolute spatial position
address (310); an absolute class address (312); and an absolute
coefficient accuracy address (314), into the compressed bitstream,
according to commands from the external parameter controller. The
control information provides decoding information for decoding at
least a forward sequence of wavelet coefficients.
The bitstream controller (302) outputs an output error resilient
bitstream (316), which is in turn coupled to a bitstream decoder
(318). The bitstream decoder performs error detection in an error
detection unit (320) in the bitstream decoder, optional error recovery
in an error recovery unit (322) in the bitstream decoder when reversible
variable length codes are present as indicated by the syntax of
the output error resilient bitstream (316), and error localization
and concealment in an error containment unit (324) in the bitstream
decoder. The bitstream decoder outputs an output decoded error concealed
image (326).
The absolute class address (312) in a predetermined wavelet coefficient
classification scheme includes classification according to at least
one of: classes of individual wavelet coefficients; classes of blocks
of wavelet coefficients; and classes of multiresolution trees of
wavelet coefficients. This enables grouping the compressed wavelet
coefficients in the output error resilient bitstream according to
a region or regions of interest in the image, or grouping the compressed
wavelet coefficients according to a scheme which is beneficial to
the improved compression of the wavelet-based image decomposition.
The error detection unit (320) is configured to detect an error
in the absolute restart address wherein at least one of: detecting
loss of entropy coding synchronization; detecting an incorrect absolute
subband address; detecting an incorrect absolute spatial position
address; detecting an incorrect absolute class address; and detecting
an incorrect absolute coefficient accuracy value are present.
As shown in FIG. 4, numeral 400, in one embodiment, the method
of the present invention may include the steps of: A) utilizing
(402), in a decoder, control information and a plurality of resynchronization
markers inserted at arbitrary positions in a wavelet-based image
bitstream wherein the control information provides decoding information
for decoding at least a forward sequence of wavelet coefficients;
and B) detecting errors (404) in an image bitstream and limiting
propagation of errors in a decoded image utilizing the control information
and the plurality of resynchronization markers.
Where selected, the control information may include decoding information
for decoding a backward sequence of wavelet coefficients utilizing
reversible entropy codewords or a resetting of predetermined predictively
encoded information at a boundary of bitstream segments and includes
an absolute restart address in a predetermined wavelet-based image
decomposition scheme.
Typically, the absolute restart address includes at least one of:
A) an absolute subband address in a predetermined wavelet decomposition
scheme; B) an absolute spatial position address in a predetermined
wavelet subband coefficient scanning scheme; C) an absolute class
address in a predetermined wavelet coefficient classification scheme;
and D) an absolute coefficient accuracy value in a predetermined
variable coefficient accuracy wavelet coding scheme
The absolute class address in the predetermined wavelet coefficient
classification scheme may include classification according to at
least one of: A) classes of individual wavelet coefficients; B)
classes of blocks of wavelet coefficients; and C) classes of multiresolution
trees of wavelet coefficients.
Generally, detecting an error in the image bitstream may include
detecting an error in the absolute restart address including at
least one of: A) detecting loss of entropy coding synchronization;
B) detecting an incorrect absolute subband address; C) detecting
an incorrect absolute spatial position address; D) detecting an
incorrect absolute class address; and E) detecting an incorrect
absolute coefficient accuracy value are present.
FIG. 5, numeral 500, is a flow chart showing another embodiment
of steps of a method of region of interest localization of a wavelet-based
image codec in accordance with the present invention, wherein wavelet
coefficients are encoded using entropy coding. In this embodiment,
the steps include: A) localizing (502), in a decoder, wavelet coefficients
associated with one or more predetermined regions of interest utilizing
control information and a plurality of resynchronization markers
wherein the control information provides information for decoding
at least one region of interest in an image; and B) detecting boundaries
(504) of regions of interest in an image bitstream and limiting
the decoding of the image bitstream to at least one region of interest
utilizing the plurality of resynchronization markers and the control
information.
Implementation of the control information, the absolute restart
address, and the absolute class address may be as described above.
As shown in FIGS. 5 and 6, the method may be selected to be a process
(500, 600) whose steps are embodied in at least one of: A) an application
specific integrated circuit (ASIC); B) a field programmable gate
array; and C) a microprocessor; and D) a computer-readable memory
that is/are arranged and configured to decode a wavelet-based image
bitstream in accordance with the invention.
For example, as shown in FIG. 6, the present invention may be a
device for error control of a wavelet-based image codec, wherein
wavelet coefficients are encoded using entropy coding, wherein the
device is directed by a computer program (606) that is embodied
in at least one of: a memory, an application specific integrated
circuit (ASIC); a digital signal processor (DSP); microprocessor;
and a field programmable gate array (FPGA) (601). The computer program
typically includes the steps of: 1) utilizing (602) control information
and a plurality of resynchronization markers inserted at arbitrary
positions in a wavelet-based image bitstream wherein the control
information provides decoding information for decoding at least
a forward sequence of wavelet coefficients; and 2) detecting (604)
errors in an image bitstream and limiting the propagation of errors
in a decoded image utilizing the control information and the plurality
of resynchronization markers. Implementation of the control information,
the absolute restart address, and the absolute class address may
be as described above.
Typically, in the steps implemented by the computer program, detecting
an error in the image bitstream includes detecting an error in the
absolute restart address include at least one of: A) detecting loss
of entropy coding synchronization; B) detecting an incorrect absolute
subband address; C) detecting an incorrect absolute spatial position
address; D) detecting an incorrect absolute class address; and E)
detecting an incorrect absolute coefficient accuracy value are present.
FIG. 7, numeral 700, is a block diagram of one embodiment of a
device for region of interest localization of a wavelet-based image
codec in accordance with the present invention, wherein wavelet
coefficients are encoded using entropy coding. The device includes:
A) a decoder (706), coupled to a boundary detector, having a wavelet
coefficient localizer (702) for localizing wavelet coefficients
associated with one or more predetermined regions of interest utilizing
control information and a plurality of resynchronization markers
wherein the control information provides information for decoding
at least one region of interest in an image; and B) the boundary
detector (704), coupled to the decoder (706), for detecting boundaries
of regions of interest in an image bitstream and limiting the decoding
of the image bitstream to one or more regions of interest utilizing
the plurality of resynchronization markers and control information.
Implementation of the control information, the absolute restart
address, and the absolute class address may be as described above.
As shown in FIG. 8, numeral 800, in a preferred embodiment a digital
camera (808) may include the device for region of interest localization
of a wavelet-based image codec, wherein wavelet coefficients are
encoded using entropy coding, in accordance with the present invention.
The device includes a decoder (806) with a wavelet coefficient localizer
(802) and a boundary detector (804) coupled and operating as described
above.
The method and device may be selected to be embodied in at least
one of: A) an application specific integrated circuit; B) a field
programmable gate array; and C) a microprocessor; and D) a computer-readable
memory; arranged and configured to decode a wavelet-based image
bitstream in accordance with the scheme described in greater detail
above.
Although exemplary embodiments are described above, it will be
obvious to those skilled in the art that many alterations and modifications
may be made without departing from the invention. Accordingly, it
is intended that all such alterations and modifications be included
within the spirit and scope of the invention as defined in the appended
claims. |