Method and apparatus for modifying the quantization step of each macro-block in a video segment

• US 5,677,734 A
• Filed: 08/15/1995
• Issued: 10/14/1997
• Est. Priority Date: 08/19/1994
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yanagihara, Naofumi, Izumi, Nobuaki, Oikawa, Yuka
• Primary Examiner(s): Chin, Tommy P.
• Assistant Examiner(s): LEE, Y YOUNG
• Application Number:
  US08/515,529
• Time in Patent Office: 791 Days
• Field of Search: 348/405, 348/419, 382/251, 341/200, 358/335, 358/342, 358/310, 360/9.1, 386/112, 386/46
• US Class Current: 375/240.04
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/192 the adaptation method, adaptation tool or adaptation type being iterative or recursive
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/88 involving rearrangement of data among different coding units, e.g. shuffling, interleaving, scrambling or permutation of pixel data or permutation of transform coefficient data among different blocks
• CPC Class Codes: H04N 7/54 the signals being synchronous H04N21/23602, H04N21/23614, H04N21/2365, H04N21/2368, H04N21/4341, H04N21/4342, H04N21/4347, H04N21/4348 take precedence
• CPC Class Codes: H04N 9/8047 using transform coding

Abstract

A method and apparatus for recording digital video signals in which digital video signals in the form of DCT coefficients, obtained by e.g., discrete cosine transform, are quantized and compressed so as to be recorded on a recording medium. A first quantization step decision unit determines a quantization step in terms of a video segment made up of plural macro-blocks as a unit so that the quantity of quantized data is less than a pre-set data quantity. A second quantization step decision unit determines a quantization step in terms of the macro-blocks as a unit so that the quantity of quantized data is less than the pre-set data quantity. A quantization unit quantizes the digital video signals with the quantization steps determined by the first quantization step decision unit and the second quantization step decision unit. This enables efficient encoding and improved picture quality.

Claims

1. A method for providing quantized and encoded digital video signals, comprising the steps of:

determining a quantization step in terms of a video segment composed of a plurality of macro-blocks as a unit so that a quantity of quantized data is less than a pre-set data quantity, wherein quantization steps for every macro-block constituting the video segment initially are equal to said determined quantization step of the video segment;

modifying the quantization steps associated with each of the plurality of macro-blocks of the video segment individually one at a time in a pre-determined order without exceeding the pre-set data quantity;

quantizing the digital video signal with the determined quantization steps associated with each of the plurality of macro-blocks.

2. The method as claimed in claim 1, wherein the step of modifying the quantization steps comprises giving priority to a macro-block which is located at a center of a picture.

3. The method as claimed in claim 1, wherein the step of determining the quantization step in terms of a video segment comprises calculating an optimum quantization step for each of the luminance signals and color signals of the video signals by arithmetic operations.

4. The method as claimed in claim 1, wherein the number of the macro-blocks in the video segment is five.

5. Apparatus for providing quantized and encoded digital video signals, comprising:

means for determining a quantization step in terms of a video segment composed of a plurality of macro-blocks as a unit so that a quantity of quantized data is less than a pre-set data quantity, wherein quantization steps for every macro-block constituting the video segment initially are equal to said determined quantization step of the video segment;

means for modifying the quantization steps associated with each of the plurality of macro-blocks of the video segment individually one at a time in a pre-determined order without exceeding the pre-set data quantity;

means for quantizing the digital video signal with the determined quantization steps associated with each of the plurality of macro-blocks.

6. The apparatus as claimed in claim 5, wherein said modifying means is operable to give priority to a macro-block which is located at a center of a picture.

7. The apparatus as claimed in claim 5, wherein the means for determining the quantization step in terms of a video segment comprises means for calculating an optimum quantization step for each of the luminance signals and color signals of the video signals by arithmetic operations.

8. The apparatus as claimed in claim 5, wherein the number of the macro-blocks in the video segment is five.