Apparatus and method for motion video encoding employing an adaptive quantizer

• US 5,301,242 A
• Filed: 08/31/1992
• Issued: 04/05/1994
• Est. Priority Date: 05/24/1991
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gonzales, Cesar A., Viscito, Eric
• Primary Examiner(s): COUSO, YON JUNG
• Application Number:
  US07/936,724
• Time in Patent Office: 582 Days
• Field of Search: 382/56, 382/50, 382/53, 358/105, 358/133, 358/135, 364/725
• US Class Current: 382/239
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/50 using predictive coding H04N19/61 takes precedence
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 5/85 on discs or drums
• CPC Class Codes: H04N 5/9264 using transform coding

Abstract

An apparatus and method for encoding of a video picture is disclosed. The video picture has a plurality of pictures. The pictures each have a plurality of macroblocks. The macroblocks each have a plurality of sub-blocks. The apparatus comprising a first module configured to generate a transform coefficient C_ij for each of the sub-blocks of the macroblock. The apparatus further comprises a second module configured to variably quantize the transform coefficient by a scaling factor Q_p based on the complexity of the picture and any rate control requirements.

Claims

1. A video encoding apparatus configured to convert groups of blocks of digital video signals into compressible groups of blocks of digital video signals, comprising:

(a) a transform coefficient device, having an input configured to receive a digital video signal representing a block of a video image, configured to generate a first signal representing a set of transform coefficients C_ij in response to said received digital video signal;

(b) an adaptive quantization device, having an input coupled to said transform coefficient device, configured to receive said first signal representing a set of transform coefficients C_ij, and to provide a second signal representing a quantized transform coefficient Cq_ij in response to said first signal representing said set of transform coefficients C_ij ;

(c) a variable length coder, having an input coupled to said adaptive quantization device, configured to receive said second signal representing said quantized transform coefficient Cq_ij and to provide a variable-rate signal having a variable bit rate and representing a compressed digital video signal in response to said second signal representing said quantized transform coefficient Cq_ij ; and

(d) a buffer, having an input coupled to said variable length coder, configured to equalize said variable bit rate of said variable-rate signal representing a compressed digital video signal and to provide a constant rate compressed digital video signal, and further configured to provide a third signal indicating buffer fullness.

2. The apparatus of claim 1, further comprising a bit allocator, coupled to said adaptive quantization device, configured to allocate a specific number of bits for each picture.

3. The apparatus of claim 1, further comprising a storage device, coupled to said buffer, configured to store said constant rate compressed digital video signal.

4. The apparatus of claim 1, wherein said second signal representing a quantized transform coefficient Cq_ij is further provided in response to said third signal indicating buffer fullness.

5. The apparatus of claim 4, wherein said second signal representing a quantized transform coefficient Cq_ij is further provided in response to complexity of the video image represented by said digital video signal.

6. The apparatus of claim 1, wherein said second signal representing a quantized transform coefficient Cq_ij is further provided in response to complexity of the video image represented by said digital video signal.

7. A video encoding apparatus configured to convert groups of blocks of digital video signals into compressible groups of blocks of digital video signals, comprising:

(a) a transform coefficient device, having an input configured to receive a digital video signal representing a block of a video image, configured to generate a first signal representing a set of transform coefficients C_ij in response to said received digital video signal; and

(b) an adaptive quantization device, having an input coupled to said transform coefficient device, configured to receive said first signal representing a set of transform coefficients C_ij, and to provide a second signal representing a quantized transform coefficient Cq_ij in response to said first signal representing said set of transform coefficients C_ij, wherein said adaptive quantization device comprises;

(1) a first multiplier configured to provide a third signal representing partially quantized video data CW_ij in response to said first signal representing a set of transform coefficients C_ij ;

(2) a q_p selection device, coupled to said first multiplier, operable to provide a fourth signal representing a quantization factor q_p in response to said third signal representing partially quantized video data C_ij ; and

(3) a second and third multiplier and an adder, configured to transform said third signal representing partially quantized video data C_ij into said second signal representing said quantized transform coefficient Cq_ij, based on said fourth signal representing said quantization factor q_p.

8. The apparatus of claim 7, further comprising:

(c) a variable length coder, having an input coupled to said adaptive quantization device, configured to receive said second signal representing said quantized transform coefficient Cq_ij and to provide a variable-rate signal having a variable bit rate and representing a compressed digital video signal in response to said second signal representing said quantized transform coefficient Cq_ij ; and

(d) a buffer, having an input coupled to said variable length coder, configured to equalize said variable bit rate of said variable-rate signal representing a compressed digital video signal and to provide a constant rate compressed digital video signal, and further configured to provide a fifth signal indicating buffer fullness.

9. The apparatus of claim 7, wherein said fourth signal representing said quantization factor q_p is further provided in response to a signal representing fullness of a rate buffer.

10. The apparatus of claim 7, wherein said q_p selection device comprises:

(a) a first max select module, having an input to receive said third signal representing partially quantized video data CW_ij, configured to determine a maximum transform coefficient for each of four blocks of each group of blocks, and to generate a firth signal representing the same;

(b) a first min select module, having an input coupled to said first max select module, configured to determine a minimum transform coefficient for each four blocks of each group of blocks, and to generate a sixth signal representing the same;

(c) a normalizing multiplier, having an input coupled to said first min select module, configured to normalize said sixth signal representing said minimum transform coefficient for each of four blocks of each group of blocks, and further configured to provide a seventh signal representing the same;

(d) a q_p min selection module, having an input coupled to said first max select module, configured to select a value of q_p that is a lower bound for q_p, and to provide an eighth signal representing the selected value of q_p min;

(e) a lower bound select module, having a first input coupled to said q_p min selection module and a second input coupled to said buffer, configured to provide a ninth signal representing a lower bound of q_p ;

(f) a second max select module, having a first input coupled to said normalizing multiplier and a second input coupled to said lower bound select module, configured to provide a tenth signal representing a value of q_p that is the greater of said seventh signal and said ninth signal; and

(g) a second min select module, having a first input coupled to said second max select module and a second input coupled to said buffer, configured to select a value for q_p that is not greater than rate control requirements allow and further configured to provide an eleventh signal representing this selected value of q_p.