Method and apparatus for transitioning from a first display format to a second display format
A letterbox detector includes a detection module configured to determine aspect ratio changes in an input signal. A transition module is configured to transition between a plurality of display modes associated with the aspect ratio changes. A first display mode to a second display mode transition is performed over a first period of time, and a second display mode to a first display mode is performed gradually over a second period of time, that is different from the first period of time. The letterbox detector may be included in digital and analog displays.
1. A letterbox detector, comprising:
a detection module configured to determine aspect ratio changes in an input signal; and
a transition module configured to transition between a plurality of display modes associated with the aspect ratio changes, wherein a first display mode to a second display mode transition is performed over a first period of time, and the second display mode to the first display mode transition is performed over a second period of time that is different from the first period of time.
2. The letterbox detector as recited in claim 1 , wherein the detection module includes a picture analyzer to determine an active area wherein the active area is compared to an active mode of a display device to determine if a transition is needed.
3. The letterbox detector as recited in claim 1 , wherein the transition module includes a plurality of time constants, each time constant being associated with a transition between different display modes.
4. The letterbox detector as recited in claim 1 , wherein one of the first and second periods of time are determined by a transition function.
5. A digital display device, comprising:
a signal processor configured to receive digital video signals and output processed video signals;
a letterbox detector configured to receive the digital video signals, determine active area changes in the digital video signals and provide display mode transition information;
a scaler configured to receive the display mode transition information and transition an active picture area using the processed video signals in accordance with the display mode transition information such that the active picture area is transitioned between a first display mode and a second display mode by a first period of time and transitioned between the second display mode and the first display mode by a second period of time that is different from the first period of time.
6. The display device as recited in claim 5 , further comprising a memory configured to receive the processed video signals and provide the processed video signals to the scaler for output in accordance with the display mode transition information.
7. The display device as recited in claim 5 , wherein the letterbox detector includes a plurality of time constants, each time constant being associated with a transition between different display modes.
8. The display device as recited in claim 5 , wherein one of the first and second periods of time are determined by a transition function.
9. The display device as recited in claim 5 , wherein at least one of the first and second periods of time is user selectable.
10. The display device as recited in claim 5 , wherein if during a transition between the first display mode and the second display mode the active picture area changes, the letterbox detector begins a new transition at a last transition position before the change.
11. A method for changing display modes in a display device, comprising:
comparing an active area of a picture to a display mode set on a display; and
if the display mode set on the display is different from the determined active area, activating an active area transition from a first display mode to a second display mode by a first period of time; and
activating an active area transition from the second display mode to the first display mode by a second period of time that is different from the first period of time.
12. The method as recited in claim 11 , wherein activating a gradual active area transition includes activating one of a plurality of time constants, each time constant being associated with a transition between different display modes.
13. The method as recited in claim 12 , wherein one of the first and second periods of time is determined by a transition function.
14. The method as recited in claim 11 , further comprising, if during a transition between the first display mode and the second display mode the active picture area changes, continuing a new transition at a last transition position before the change.