Image analysis – Image compression or coding – Including details of decompression
Reexamination Certificate
1997-12-31
2001-08-14
Boudreau, Leo (Department: 2721)
Image analysis
Image compression or coding
Including details of decompression
C382S248000, C382S250000, C382S298000, C382S232000, C348S390100, C348S395100
Reexamination Certificate
active
06275616
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to multimedia images and digital communications, and more particularly to a method and apparatus for converting a high definition image to a relatively lower definition image using wavelet transforms.
BACKGROUND OF THE INVENTION
The introduction of high definition television (HDTV) has generated a large amount of publicity because of the superior performance characteristics of HDTV relative to standard definition television (SDTV). HDTV offers approximately twice the veritical and horizontal resolution of standard definition television (SDTV), providing picture quality approaching that of 35 mm film. Since HDTV signals are digital and virtually free of noise, HDTV offers sound quality approaching that of a compact disc (CD) and does not suffer from some of the shortcomings of SDTV such as crosscolor and crosslumina. HDTV also has lower transmission costs because of error correction codes currently only available with digital formats. In addition, HDTV provides multicasting, which enables broadcasters to split programming transmission into multiple channels, and a higher level of interactivity than SDTV, allowing end users to manipulate a television program at the point of reception.
Despite the technical advantages that HDTV provides over SDTV, the widespread implementation and acceptance of HDTV as a new standard depends upon the resolution of several important issues. One of the most important issues is how to implement HDTV while continuing to support the large number of existing SDTV display devices already in use. Most SDTV display devices cannot decode an HDTV signal and cannot be used in a pure HDTV broadcast environment. Moreover, the relatively high cost of HDTV display devices makes replacing existing SDTV display devices with HDTV display devices impractical. Thus, a widespread implementation of HDTV must address the problem of how to support the existing SDTV display devices currently in use.
One solution to this problem is for service providers to transmit programs in both HDTV and SDTV formats (simulcast). This could be done by transmitting both an HDTV signal and an SDTV signal, or by augmenting an SDTV signal with additional information necessary to “enhance” the SDTV signal to provide a HDTV signal. With this approach, SDTV display devices only process the SDTV portion of the signal while ignoring the additional information. On the other hand, HDTV display devices process both the SDTV signal information and the additional information. Although this approach solves the problem of how to implement HDTV while supporting existing SDTV display devices, it consumes a considerable portion of the available distribution bandwidth making it very undesirable to service providers.
An alternative solution is for service providers to transmit programs in HDTV format only and for all display units to incorporate a special decoder, sometimes referred to as an “all format decoder,” that has the ability to decode both standard definition (SD) and high definition (HD) video from the HDTV signal. This approach is attractive from several standpoints. First, an all format decoder can be included in all new HDTV display devices. In addition, an all format decoder can be sold separately as a stand-alone unit that can be attached to existing SDTV display devices. This allows new HDTV display devices can take full advantage of the new HDTV technology while allowing existing SDTV display devices to continue to be used.
Conventional all-format decoders consist of an SDTV decoder, e.g. an MPEG-2 decoder, with a number of enhancements. An HDTV signal is first preprocessed to discard or decimate information that is not needed for a standard definition display, such as high-frequency coefficients. This reduces the amount of data in the preprocessed HDTV signal, reducing the required bandwidth and allowing a smaller channel buffer to be used. The reduced amount of data also simplifies subsequent processing of the preprocessed signal.
Next, the remaining portions of the encoded image data are decoded using any of the well known video sampling techniques such as a high definition 4:4:4 video sampling technique, or a lower definition video sampling technique such as 4:2:2 or 4:2:0. Conventional MPEG decoders use an inverse discrete cosine transform (IDCT) process to decode video-related data that was previously encoded using a discrete cosine transform (DUCT) process.
Digital Video: An Introduction To MPEG
-2 by Barry G. Haskell, Atul Puri and Arun N. Netravali, provides useful background information on decoding video-related data and is incorporated by reference herein in its entirety.
Image data encoded and decoded by conventional encoders and decoders typically includes luminance data (Y
C
) and two types of chrominance data referred to as (U
C
) and (V
C
). To display a high definition image (1920 by 1080 pixels), a typical decoder provides 1920 by 1080 pixels of luminance-related data and 960 by 540 pixels of chrominance-related data. The resulting data provides a 4:2:0 image having 1920 by 1080 pixels.
Following the decoding process, the decoded image data is then filtered and/or decimated to further reduce the image for display on a lower resolution display. By way of example, the lower definition image provided by certain decoders is ¼ the size (¼ number of pixels) of the original higher definition image. Thus, for a 1920 by 1080 pixel image (2,073,600 total pixels), the lower definition image is 960 by 540 pixels (518,400 pixels). Thus, a lower definition image has less information than a higher definition image.
Consider the conventional system
100
illustrated in
FIG. 1
for encoding, transmitting and decoding image data. An image is scanned or otherwise processed to create image data
102
, which is typically in the form of an image file. Image data
102
is provided to an encoder
104
. Encoder
104
encodes image data
102
and provides encoded image data The encoded image data is transmitted to a decoder
106
via a link
108
. Link
108
can include one or more communication mediums and/or systems and supporting apparatuses that are configured to carry the encoded image data between encoder
104
and decoder
106
. Examples of link
108
include, but are not limited to, a telephone system, a cable television system, a broadcast television system (direct or indirect), a satellite broadcast system (direct or indirect), one or more computer networks and/or buses, the Internet, an intranet, and any software, hardware and other communication systems and equipment associated therewith for transmitting encoded data between two locations.
Decoder
106
decodes the encoded image data received from encoder
104
and provides decoded image data
110
that is suitable for reproduction with a display
112
. Ideally, decoded image data
110
is identical to image data
102
. However, limitations in the encoding and decoding processes performed by encoder
104
and decoder
106
respectively, sometimes alter the data, adversely affecting the quality of decoded image data
110
when displayed on display
112
.
In certain embodiments, encoder
104
and/or decoder
106
include one or more processors that each are coupled to a memory. The processor(s) respond to computer implemented instructions stored within the memories to encode or decode image data
102
as required. In other embodiments, encoder
104
and/or decoder
106
include logic that is configured to encode or decode image data
102
as required.
FIG. 2A
is a block diagram depicting a conventional system
200
for reducing a high definition image to a lower definition image. Image data
202
is provided to an encoder
204
that encodes image data
202
and provides encoded image data. Encoder
204
includes a DCT process
206
that encodes image data
202
using a DCT.
The encoded image data provided by encoder
204
is transmitted to a decoder
208
via a link
210
. Link
210
communicatively couples encoder
204
and decoder
208
and provides for the transmission of d
Chaney Jack
Jahanghir Musa
Kaufman Michael A.
Aiello Jeffrey P.
Boudreau Leo
Mariam Daniel G.
Samsung Electronics Co,. Ltd.
Sherman & Sherman
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