Video signal processing
View Patent ↗A video signal processing apparatus for processing a video signal comprises a receive unit ( 101, 103, 105 ) which receives the video signal comprising a sequence of pictures. A processing unit ( 107 ) applies a picture noise changing algorithm to the sequence of pictures and a variation unit ( 113 ) varies a spatial noise reduction setting for the picture noise changing algorithm between at least some consecutive pictures of the sequence of pictures in response to a predetermined variation rule. Specifically a set of picture manipulation processes ( 203, 205 ) with different spatial noise reduction characteristics may be provided and the variation unit ( 113 ) may select different picture manipulation processes in consecutive pictures. The approach may introduce high frequency noise flickering which is less perceptible to a viewer thereby reducing the perceived noise. The invention may in particular be applied to upconverted high picture rate video signals for hold type displays, such as Liquid Crystal Displays displays.
1. A video signal processing apparatus for processing a video signal, the apparatus comprising:
a processing unit for applying a picture noise changing algorithm, the processing unit including:
a switch unit having a first input for receiving the video signal, the video signal having a sequence of frames, a second input, a first output and a second output, the switch unit selecting, based upon a signal received at the second input, whether frames received at the switch unit input are to be directed to the first or second output;
a first noise reduction unit having a input and an output, the input being coupled to the first output of the switch unit;
a second noise reduction unit having an input and an output, the input being coupled to the second output of the switch unit; and
a frame combiner having a first input and a second input, the first input coupled to the output of the first noise reduction unit and the second input coupled to the output of the second noise reduction unit;
a variation unit for varying a noise reduction setting for the picture noise changing algorithm between at least some consecutive pictures of the sequence of pictures in response to a predetermined variation rule, wherein said varying is independent of the received pictures, the variation unit having an output coupled to the second input of the switch unit for providing signals to the switch unit which determine whether frames received by the switch unit are to be output via the first output of the switch unit or the second output of the switch unit, and thus varying the noise reduction setting.
2. The video signal processing apparatus of claim 1 , wherein the first and second noise reduction unit each perform a set of picture manipulation processes, each picture manipulation process of the set of executable picture manipulation processes having a different noise reduction characteristic.
3. The video signal processing apparatus of claim 2 wherein the predetermined variation rule comprises a predetermined alternating sequence for the different picture manipulation processes.
4. The video signal processing apparatus of claim 2 , wherein the processing unit further comprises:
a noise estimator for generating a noise estimate for a first picture of the at least some consecutive pictures; and wherein at least a first picture manipulation process of the set of picture manipulation processes is arranged to adjust a noise reduction characteristic in response to the noise estimate when the first picture manipulation process is applied to the first picture.
5. The video signal processing apparatus of claim 2 wherein at least one picture manipulation process of the set of picture manipulation processes is an edge preserving spatial noise reduction process.
6. The video signal processing apparatus of claim 2 wherein the picture manipulation processes of the set of picture manipulation processes are spatial noise reduction processes.
7. The video signal processing apparatus of claim 1 further comprising a frame rate upconverter arranged to generate the sequence of pictures as a sequence of upconverted frames generated from a lower frame rate video signal.
8. The video signal processing apparatus of claim 7 wherein the predetermined variation rule prescribes increasing spatial noise reduction for an increasing difference in time between an upconverted frame of the sequence of upconverted frames and an original frame.
9. The video signal processing apparatus of claim 1 wherein a noise reduction setting variation introduced by the variation unit is independent of characteristics of the at least some consecutive pictures.
10. The video signal apparatus of claim 3 wherein the predetermined variation rule is such that a variation frequency of the noise reduction setting is above 30 Hz.