Complexity control of video codec

A method for adaptive use of image frame processing resources comprising a central processing unit connected to at least one memory, the central processing unit being configured to receive frames of a video signal, the method comprising:

• each frame being split into coding units comprising pixels,
• defining a threshold for a rate distortion cost error,
• a difference between a corresponding complexity and a complexity threshold is stored in the memory as a reference for calculation of an updated rate distortion cost error threshold,
• wherein the difference between the complexity resulting from the updated rate distortion cost error threshold, and the former complexity threshold is smaller or equal to the difference between the former complexity and the complexity threshold,
• recursively splitting coding units into a quad-tree structure of different coding units having levels and sub-levels, wherein in a quad-tree structure, each level or sub-level is recursively split into parts, a depth of a specific coding unit being defined by the number of recursive splits of coding units that have been used in order to reach the specific coding unit, wherein the size of the specific coding unit is the maximum size divided by the number of recursive splits, and
• wherein the coding unit at a certain depth being encodable with the second number of different coding modes, the determining of the second number being such as to maximise the use of dynamically for the encoder available image frame processing resources.

A method for adaptive use of image frame processing resources comprising a central processing unit connected to at least one memory, the central processing unit being configured to receive frames of a video signal, the method comprising:

• each frame being split into coding units comprising pixels,
• defining a threshold for a rate distortion cost error,
• a difference between a corresponding complexity and a complexity threshold is stored in the memory as a reference for calculation of an updated rate distortion cost error threshold,
• wherein the difference between the complexity resulting from the updated rate distortion cost error threshold, and the former complexity threshold is smaller or equal to the difference between the former complexity and the complexity threshold, and
• estimating the rate distortion cost comprising all coding modes by assuming said cost is proportional to a linear model of the rate distortion cost comprising less than all coding modes,
• wherein an estimated rate distortion cost is linearly proportional to the rate distortion cost comprising all coding modes multiplied by the coefficient 0.87, 0.92, 0.94, 0.95 for the depth 0, 1, 2 and 3 respectively.

A system for adaptive use of image frame processing resources comprising:

• a central processing unit connected to at least one memory, the central processing unit being configured to receive frames of a video signal, each frame being split into coding units comprising pixels,
• the central processing unit defining a rate distortion cost error threshold, a difference between the corresponding complexity and a complexity threshold is stored in the memory as a reference for a calculation of an updated rate distortion cost error threshold,
• wherein the difference between the complexity resulting from the updated rate distortion cost error threshold, and the former complexity threshold is smaller or equal to the difference between the former complexity and the complexity threshold,
• wherein the system is configured to be used for video compression, wherein the image frame processing resources vary dynamically in time,
• wherein the video signal comprises image frames processed at a video rate, wherein an image frame is expressed in a number of coding units, a coding unit having a predefined maximum size,
• a controller being adapted to receive said image frame, the coding unit being encodable with a first number of different coding modes,
• wherein the central processing unit is configured to determine a rate distortion cost for a second number of different coding modes, the second number being less or equal to the first number of different coding modes for the specific coding unit, the difference between an estimated rate distortion cost for the first number and the rate distortion cost determined for the second number of coding modes is the rate distortion cost error, and the difference between the rate distortion cost error and a targeted rate distortion cost error has a minimum value for a certain coding mode, said coding mode is selected to encode the coding unit.