US 8,711,925 B2 · Flexible quantization

Abstract

A digital media encoder/decoder uses a flexible quantization technique that provides the ability to vary quantization along various dimensions of the encoded digital media data, including spatial, frequency sub bands and color channels. The codec utilizes a signaling scheme to signal various permutations of flexible quantization combinations efficiently for primary usage scenarios. When a choice of quantizer is available, the codec efficiently encodes the current quantizer by defining a subset of quantizers and indexes the current quantizer from the set.

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Claims17

Dependent claims

A method of decoding digital media, comprising:

with a computer,
receiving compressed digital image data, the compressed digital image data having been partitioned along more than one dimension;
determining multiple sets of quantization parameter indices from signals in the compressed digital image data, the compressed digital image data having been quantized across more than one partitioned dimension of the digital image data, the signals indicating whether quantization parameter indices used during decoding vary within a frequency band dimension and within a color channel dimension, the quantization parameter indices available across the frequency band dimension including, for a given set of the multiple sets of quantization parameter indices, a first quantization parameter index for one or more DC components, a second quantization parameter index for multiple low-pass components, and a third quantization parameter index for multiple high-pass components;
for each of multiple macroblocks of the compressed digital image data:
selecting one of the multiple sets of quantization parameter indices based on a value signaled for the macroblock;
and
determining one or more quantization parameters for the selected set of quantization parameter indices;
dequantizing the compressed digital image data in accordance with the determined quantization parameters;
applying an inverse of a block transform to blocks of the dequantized digital image data;
and
outputting decompressed digital image data,
wherein:
(a) the multiple high-pass coefficients are AC coefficients from first transforms of values of blocks of a macroblock;
(b) the multiple low-pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms;
and (c) the one or more DC coefficients include a DC coefficient from the second transform of the DC coefficients from the first transforms.

12 more elements

At least one memory device or magnetic disk having program code stored thereon for causing a digital media processing device to perform a method of processing digital media data according to a codec, the method comprising:

selecting combinations of available quantization modes to be applied to the digital media data, the available quantization modes including at least a first quantization mode in which low pass coefficients use the same quantizer as a DC coefficient and a second quantization mode in which high pass coefficients use the same quantizer as low pass coefficients, the first quantization mode being signaled by a first syntax element, the second quantization mode being signaled by a second syntax element;
applying a two-stage transform to blocks of the digital media data;
quantizing the digital media data according to the selected combinations of quantization modes;
encoding the quantized digital media data in a compressed data stream;
and
signaling the selected combinations of quantization modes in the compressed data stream, the compressed data stream including the first syntax element and the second syntax element,
wherein the high pass coefficients are AC coefficients from first transforms of values of the blocks, and wherein the low pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms.

4 more elements

receiving compressed digital image data;
determining multiple sets of quantization parameter indices from signals in the compressed digital image data, the signals indicating whether quantization parameter indices used during decoding vary within a frequency band dimension and within a color channel dimension, the quantization parameter indices available across the frequency band dimension including, for a given set of the multiple sets of quantization parameter indices, a first quantization parameter index for one or more DC components, a second quantization parameter index for multiple low-pass components, and a third quantization parameter index for multiple high-pass components;
for each of multiple macroblocks of the compressed digital image data:
selecting one of the multiple sets of quantization parameter indices based on a value signaled for the macroblock;
and
determining one or more quantization parameters for the selected set of quantization parameter indices;
dequantizing the compressed digital image data in accordance with the determined quantization parameters;
applying an inverse of a block transform to blocks of the dequantized digital image data;
and
outputting decompressed digital image data,
wherein (a) the multiple high-pass coefficients are AC coefficients from first transforms of values of blocks of a macroblock;
(b) the multiple low-pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms;
and (c) the one or more DC coefficients include a DC coefficient from the second transform of the DC coefficients from the first transforms.

10 more elements

Dependencies are inferred from the claim text.

Description6,111 words

Summary1,456 words

#1. Block Transform-Based Coding

#Transform coding is a compression technique used in many audio, image and video compression systems. Uncompressed digital image and video is typically represented or captured as samples of picture elements or colors at locations in an image or video frame arranged in a two-dimensional (2D) grid. This is referred to as a spatial-domain representation of the image or video. For example, a typical format for images consists of a stream of 24-bit color picture element samples arranged as a grid. Each sample is a number representing color components at a pixel location in the grid within a color space, such as RGB, or YIQ, among others. Various image and video systems may use various different color, spatial and time resolutions of sampling. Similarly, digital audio is typically represented as time-sampled audio signal stream. For example, a typical audio format consists of a stream of 16-bit amplitude samples of an audio signal taken at regular time intervals.

#Uncompressed digital audio, image and video signals can consume considerable storage and transmission capacity. Transform coding reduces the size of digital audio, images and video by transforming the spatial-domain representation of the signal into a frequency-domain (or other like transform domain) representation, and then reducing resolution of certain generally less perceptible frequency components of the transform-domain representation. This generally produces much less perceptible degradation of the digital signal compared to reducing color or spatial resolution of images or video in the spatial domain, or of audio in the time domain.

Brief description of the drawings15 figures

#FIG. 1 is a block diagram of a conventional block transform-based codec in the prior art.

#FIG. 2 is a flow diagram of a representative encoder incorporating the block pattern coding.

#FIG. 3 is a flow diagram of a representative decoder incorporating the block pattern coding.

Detailed description4,308 words

#The following description relates to coding and decoding techniques that provide efficient flexible quantization that can vary the quantization applied along spatial, frequency and color dimensions (referred to herein as “Flexible Quantization”). The following description describes an example implementation of the technique in the context of a digital media compression system or codec. The digital media system codes digital media data in a compressed form for transmission or storage, and decodes the data for playback or other processing. For purposes of illustration, this exemplary compression system incorporating this flexible quantization is an image or video compression system. Alternatively, the technique also can be incorporated into compression systems or codecs for other 2D data. The flexible quantization technique does not require that the digital media compression system encodes the compressed digital media data in a particular coding format.

#1. Encoder/Decoder

#FIGS. 2 and 3 are a generalized diagram of the processes employed in a representative 2-dimensional (2D) data encoder 200 and decoder 300. The diagrams present a generalized or simplified illustration of a compression system incorporating the 2D data encoder and decoder that implement the block pattern coding. In alternative compression systems using the block pattern coding, additional or fewer processes than those illustrated in this representative encoder and decoder can be used for the 2D data compression. For example, some encoders/decoders may also include color conversion, color formats, scalable coding, lossless coding, macroblock modes, etc. The compression system (encoder and decoder) can provide lossless and/or lossy compression of the 2D data, depending on the quantization which may be based on a quantization parameter varying from lossless to lossy.

Facts

Application

11/418,690Filed 5 May 2006

Published

US 2007/0258518 A18 Nov 2007

Granted

29 Apr 2014

Term ends

19 Sep 2030

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 1,598 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification7 codes

H04N 19/124
Characterised by the element, parameter or selection affected or controlled by the adaptive coding: quantisation
H04N 19/126
Quantisation: details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
H04N 19/136
Characterised by the element, parameter or criterion affecting or controlling the adaptive coding: incoming video signal characteristics or properties
H04N 19/176
The unit being an image region, e.g. an object: the region being a block, e.g. a macroblock

Timeline

5 May 2006Application filedUS 11/418,690
12 Apr 2007Assigned to Microsoft Corporationassignment of assignor's interest
8 Nov 2007PublishedUS 2007/0258518 A1
29 Apr 2014GrantedUS 8,711,925 B2
9 Dec 2014Assigned to Microsoft Technology Licensing, LLCassignment of assignor's interest
12 Oct 2026TodayWithin its term
19 Sep 2030Term endsEstimated, includes 1,598 days of adjustment

Flexible quantization

Life of this patent

Flexible quantization

Life of this patent

Life of this patent

Abstract

Drawings

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Claims17

Description6,111 words

Drawings

Classification7 codes

Life of this patent

Description6,111 words