Video encoder which uses intra-coding when an activity level of a current macro-block is smaller than a threshold level

• US 5,682,204 A
• Filed: 12/26/1995
• Issued: 10/28/1997
• Est. Priority Date: 12/26/1995
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: C-Cube Corporation (Broadcom, Inc.)
• Inventors: Wells, Aaron, Uz, K. Metin
• Primary Examiner(s): Britton, Howard W.
• Assistant Examiner(s): VINCENT, DAVID ROBERT
• Application Number:
  US08/578,231
• Time in Patent Office: 672 Days
• Field of Search: 348/409, 348/390, 348/393-395, 348/398, 348/400-422, 348/699
• US Class Current: 375/240.15
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/142 Detection of scene cut or scene change
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• 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 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/436 using parallelised computational arrangements
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A rate control algorithm for an MPEG-2 compliant encoder is described. The rate control algorithm has embodiments useful for constant bit rate and variable bit rate encoding.

In particular, the invention relates to a quantization biased, activity based inter/intra decision.

Claims

1. In an encoder for coding a sequence of video frames to generate a compressed bitstream, a method for determining whether to use intra-coding or inter-coding to code a macroblock in a frame, said method comprising the steps of

coding said macroblock in said encoder using intracoding:

(1) if an intra-activity of said macroblock is smaller than a threshold,

(2) if a displaced frame difference activity of said macroblock is larger than said intra-activity of said macroblock plus an intra-bias of said macroblock,

wherein said intra-bias of said macroblock is a function of a quantization scale factor utilized by said encoder to code said macroblock, said intra-bias of said macroblock increasing with increasing quantization scale factor.

2. The method of claim 1 wherein said intra-bias of said macroblock is proportional to the product of said quantization scale factor and said intra-activity of said macroblock.