Single-pass variable bit-rate control for digital video coding

An integrated digital video processing system comprising:

• an MPEG-2 compliant real-time digital image encoding subsystem for receiving an input video signal including a plurality of groups of pictures (GOPs), and generating therefrom, in a single processing pass, an output encoded video signal, such multiple GOPs being processed effectively in a look-ahead factor associated with a plurality of GOPs in a specified bit-stream sequence;
• and
• digital signal processing means coupled to such subsystem for processing the video signal to determine a variable bit rate limited by a bit rate constraint associated with such multiple GOPs, such bit rate constraint comprising a peak bit rate and an averaged bit rate, being pre-specified or dynamically re-specified for one or more current or future GOPs, wherein each of said multiple GOPs comprises at least one I-type picture, said I-type picture delimiting each of said multiple GOP from other GOPs of said multiple GOPs.

A single-pass variable bit rate controller comprising:

• an activity calculator for receiving a signal comprising a plurality of macroblocks including a plurality of groups of pictures (GOPs), and determining an activity measure for each such macroblocks and a bit rate constraint comprising a peak bit rate and an averaged bit rate associated with each such macroblocks;
• and
• a rate controller coupled to the activity calculator for processing the received signal to determine a quantization parameter to provide variably a bit rate according to the bit rate constraints, such multiple GOPs being processed effectively in a look-ahead factor associated with a plurality of GOPs in a specified bit-stream sequence, wherein each of said multiple GOPs comprises at least one I-type picture, said I-type picture delimiting each of said multiple GOP from other GOPs of said multiple GOPs.

A process for generating a variable bit rate signal comprising the steps of:

• determining a bit rate range for one or more groups of pictures (GOPs) in a digital video bit stream and a bit rate constraint comprising a peak bit rate and an averaged bit rate associated with multiple GOPs;
• and
• generating in a single processing pass according to the bit rate constraint an encoded signal from the digital video bit stream, the encoded signal having a bit rate which is controllable within the bit rate range, such multiple GOPs being processed effectively in a look-ahead factor associated with a plurality of GOPs in a specified bit-stream sequence, wherein each of said multiple GOPs comprises at least one I-type picture, said I-type picture delimiting each of said multiple GOP from other GOPs of said multiple GOPs.