Compression based reduced memory video decoder

• US 6,222,886 B1
• Filed: 06/24/1996
• Issued: 04/24/2001
• Est. Priority Date: 06/24/1996
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Yogeshwar, Jay
• Primary Examiner(s): Britton, Howard
• Assistant Examiner(s): DIEP, NHON THANH
• Application Number:
  US08/669,218
• Time in Patent Office: 1,765 Days
• Field of Search: H04/N.712, H04/N 1.102, H04/N 1.1021, 348/392, 348/424, 348/425, 348/397, 348/398, 348/400, 348/405, 348/408-411, 348/412, 348/384, 348/390, 382/233, 382/235, 375/240
• US Class Current: 375/240.23
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/40 using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• CPC Class Codes: H04N 19/423 characterised by memory arrangements H04N19/433 takes precedence
• CPC Class Codes: H04N 19/428 Recompression, e.g. by spatial or temporal decimation
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A compressed video decoder receives a stream of compressed video data in a channel buffer, and decompresses it. A portion of the decompressed video data is recompressed as intraframe data to serve as an anchor frame. The intraframe data is motion compensated, and then a reference picture is selected. The reference frame data is decompressed. Next, a region of interest is selected and stored in display memory for the decompressed form. The recompression of data to be used as an anchor frame can be done in a substantially lossless manner by using DCT with the same quantization matrix, quantizer scale, and field/frame coding type.

Claims

1. A method for decoding compressed video data, comprising the steps of:

receiving compressed video data in a channel buffer, said compressed video data including a quantization matrix, a quantizer scale, and a field/frame coding type;

decompressing said compressed video data and transferring said decompressed video data to a display memory;

recompressing a portion of said decompressed video data as intraframe data, to be used as an anchor frame, using a discrete cosine transform, said quantization matrix, said quantizer scale, and said field/frame coding type for the recompression, and storing said intraframe data, said quantization matrix, said quantizer scale, and said field/frame coding type in a compressed anchor frame storage;

motion compensating said intraframe data;

selecting a reference picture from said intraframe data; and

decompressing a region of interest of said reference picture.

2. The method of claim 1, wherein said receiving, decompressing, recompressing, motion compensating, and selecting steps occur in a decoder built into an encoder.

3. A compressed video decoder comprising:

a channel buffer for receiving compressed video data, the compressed video data having a quantization matrix, a quantizer scale, and a field/frame coding type;

first decompressing means for decompressing the compressed video data and transferring the decompressed video data to a display memory;

discrete cosine transform means for recompressing a portion of the decompressed video data as intraframe data, to be used as an anchor frame, using a discrete cosine transform, said quantizer scale, said quantization matrix, and said field/frame coding type for the recompression;

anchor frame storage means for storing the intraframe data, said quantizer scale, said quantization matrix, and said field/frame coding type;

means for motion compensating the intraframe data;

means for selecting a reference picture from the intraframe data; and

a second decompression means for decompressing a region of interest of said reference picture.

4. The decoder of claim 3, wherein said first decompressing means includes an inverse discrete cosine transform means, configured to time share as said discrete cosine transform means.

5. The decoder of claim 3, wherein the decoder is built into an encoder.