Variable bitrate video coding method and corresponding video coder

• US 6,205,174 B1
• Filed: 07/23/1998
• Issued: 03/20/2001
• Est. Priority Date: 07/29/1997
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Kaiser, Daniel, Fert, Etienne
• Primary Examiner(s): Lee, Richard
• Application Number:
  US09/121,574
• Time in Patent Office: 971 Days
• Field of Search: H04/N.732, 348/384, 348/390, 348/400-402, 348/405, 348/407, 348/409-413, 348/415, 348/416, 348/419, 348/420, 348/699, 348/700, 375/240, 375/240-2-2, 375/240-2-2, 375/240.24, 382/232, 382/236, 382/238, 382/239, 382/251
• US Class Current: 375/240.03
• CPC Class Codes: H04N 19/114 Adapting the group of pictures [GOP] structure, e.g. number of B-frames between two anchor frames H04N19/107 takes precedence
• 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 19/149 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 19/177 the unit being a group of pictures [GOP]
• CPC Class Codes: H04N 19/179 the unit being a scene or a shot
• CPC Class Codes: H04N 19/192 the adaptation method, adaptation tool or adaptation type being iterative or recursive
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/87 involving scene cut or scene change detection in combination with video compression

Abstract

A variable bitrate coding method includes an iterative process including a first analysis pass and a second prediction pass. Further, followed by a last control step for adjusting a stepsize with respect to a target bitrate. A picture re-arrangement step is also provided between the analysis and prediction steps of one iteration, in order to encode with an improved quality the picture sequence. This coding method is applicable to MPEG-2 encoders for storage media with limited capacity.

Claims

1. A variable bitrate video coding method including an iterative process that comprises a first analysis step, for coding a bitstream corresponding to a picture sequence with a constant quantization stepsize, and a second prediction step, for predicting the quantization stepsize which must then be used to code said bitstream according to a predetermined target bit rate, and is followed by a final control step, for adjusting the stepsize with respect to said target bit rate, said method including, between the analysis and prediction steps of one iteration, a picture re-arrangement step;

said picture re-arrangement step includes in series a first scene change detection sub-step, a second allocation sub-step, and a third optimum placement sub-step;

wherein said allocation sub-step is based on the implementation of a Viterbi algorithm allowing to select a preferred size for successive groups of pictures while matching a scene change with the start of such a group of pictures.

2. A variable bitrate video coding method including an iterative process that comprises a first analysis step, for coding a bitstream corresponding to a picture sequence with a constant quantization stepsize, and a second prediction step, for predicting the quantization stepsize which must then be used to code said bitstream according to a predetermined target bit rate, and is followed by a final control step, for adjusting the stepsize with respect to said target bit rate, said method including, between the analysis and prediction steps of one iteration, a picture re-arrangement step;

said picture re-arrangement step includes in series a first scene change detection sub-step, a second allocation sub-step, and a third optimum placement sub-step;

wherein said optimum placement sub-step comprises a first long-term optimization operation, for finding over several groups of pictures the optimum spacing between the pictures of these groups, and a second short-term optimization operation, for finding inside a group of pictures the best places of predicted and interpolated pictures.