Systems for MPEG subsample decoding

• US 7,016,419 B2
• Filed: 05/28/2004
• Issued: 03/21/2006
• Est. Priority Date: 04/23/2001
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Tardif, John A.
• Primary Examiner(s): An, Shawn S.
• Application Number:
  US10/856,604
• Publication Number:
  US 20040218678A1
• Time in Patent Office: 662 Days
• Field of Search: 375/240.25, 375/240.21, 375/240.16, 375/240.12, 375/240.26, 375/240.17, 348/699, 382/233, 382/235, 382/238, 382/236
• US Class Current: 375/240.25
• CPC Class Codes: G06T 3/4084 in the transform domain, e.g. fast Fourier transform [FFT] domain scaling
• CPC Class Codes: H04N 19/428 Recompression, e.g. by spatial or temporal decimation
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 19/48 using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data motion estimation in a transform domain H04N19/547; processing of decoded motion vectors H04N19/513
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/90 using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals

Abstract

Decimating MPEG or other video data by subsampling the output of an inverse discrete cosine transform (IDCT) module. The decimation process is useful for reducing the volume of data that must be processed to display images on a display device, particularly when the volume of video data received at the decoder is greater than the amount needed to take advantage of the resolution of the display device. For example, high definition television data can be decimated for display on a standard television display device or in a picture-in-picture window, thereby reducing the amount of processing resources needed at the decoder and reducing the size of the frame buffers. Subsampling the output of the IDCT module reduces the volume of data and, for relatively static or constant pans, there is not a significant compounded loss of image quality as successive frames are decoded.

Claims

1. A computer program product for implementing, in a system for processing MPEG data in preparation for displaying video images encoded in the MPEG data, a method for subsampling the MPEG data to reduce the volume of video data processed to selectively display video images based on a reduced volume of video data, the computer program product comprising:

a computer-readable medium carrying computer executable instructions capable of causing the system to perform the acts of

processing the MPEG data to generate a reconstructed digital video stream capable of producing video images in a first video resolution;

receiving a request for displaying video images having a second video resolution;

subsampling the MPEG data to obtain a reduced volume reconstructed digital video stream corresponding to the second video resolution that is less than the first video resolution, wherein the subsampled MPEG data is subsampled without generating a version of the subsampled data in the first video resolution, wherein subsampling includes decimating IDCT output data by a selected factor to generate decimated IDCT output data, and wherein decimating the IDCT output data includes weighting color parameters of at least first and second IDCT output data samples using at least first and second weighting factors, respectively, and summing the weighted color parameters; and

selectively presenting either or both of the first and second reconstructed digital video streams.

2. The invention of claim 1 wherein the act of subsampling comprises:

processing one or more motion vectors in order to produce coordinates for fetching prediction data from a previously decoded and subsampled reference frame;

processing the reference frame and the one or more motion vectors of the MPEG data using a frame prediction module to generate predicted subsampled frame data;

processing frequency coefficients of the MPEG data using an inverse discrete cosine transformer (IDCT) to generate the IDCT output data; and

summing the subsampled predicted frame data and the decimated IDCT output data to generate video images encoded in a reduced volume of video data.

3. The invention as recited in claim 2, wherein the act of decimating the IDCT output by a selected factor comprises the act of decimating the IDCT output by a first factor in a first direction and a second factor in a second perpendicular direction, such that the IDCT output is decimated by the selected factor.

4. The invention as in claim 2, further comprising the act of identifying the selected factor, the selected factor being identified to reduce the volume of MPEG data that is to be processed to display the video images and to retain enough video data to display the video images at tile first video resolution.

5. The invention as in claim 2, wherein the MPEG data, prior to the act of decimating, is formatted for display on a display device with the first video resolution, the computer-executable instructions, when executed at the system, further causing the system to perform the act of displaying the generated video images on a display device having the second video resolution.

6. The computer program product as recited in claim 5, wherein:

the display device having the first video resolution is a high definition television; and

the display device having the second video resolution is a standard television.

7. The computer program product as recited in claim 2, wherein the computer-executable instructions, when executed at the system, further cause the system to perform the act of displaying the video images in a window in a picture-in-picture display, the window having the second video resolution.