Reducing the memory of compression Feedforward driving for a new LCD controller

Abstract

Abstract— The authors have studied a method of reducing the frame memory for signal processing used to improve the response time of liquid crystals. Compared with cases in which quantization is used, the compression Feedforward driving method, which reduces frame memory by applying an image‐compression technique, can effectively reduce the frame‐memory size. The study revealed that errors decrease by 6–10 dB or so if the image data was reduced to 1/3 by means of image compression. Based on the results of the study, the authors have developed a second‐generation LCD controller. With just one SDRAM unit, this LCD controller can produce almost ideal processing effects.

Motion adaptive CODEC Feedforward Driving for LCD overdrive

“…The images in (e) and (f) of macFFD(8) have slightly more errors than cFFD-S, but if they are compared with cFFD-D, they contain fewer errors. If we look at the contour area of image (i) of cFFD-D, in particular, we can clearly see that errors are spread wider than (c) of cFFD-S and (f) of macFFD (8). This spreading of errors comes from the overlapping separate errors caused by the two decompression circuits.…”

“…However, cFFD-S allows a problem of overdrive processing to arise even on still images whose data remains unchanged over time. 8 Some of the decompressed image data differs from the original image data because it contains CODEC errors. These CODEC errors have smaller values than the dynamic range of the image data, and therefore they have little effect on moving images, whose data gradually changes.…”

“…1 As for the second-generation overdrive technique, a Compression Feedforward Driving (cFFD) unit has already been developed. 8 This cFFD method has achieved both the retention of overdrive performance and cost reduction by applying the image compression technique to the frame memory reduction method. Further, the authors are continuing to study increasing performances of their overdrive with memory reduction, 9,10 This paper reports the results of the authors' study of Motion Adaptive CODEC Feedforward Driving (macFFD), in which a motion adaptation process is added to the CODEC section in order to reduce the amount errors in overdrive, which are caused by the memory reduction.…”

33.2: Development of Single Chip Overdrive LSI with Embedded Frame Memory

“…The cFFD developed in 2002 consists of an encoding circuit and two decoding circuits as shown in Fig. 1 [1]. First, temporal variations in the pixels are determined from the two-frame decoded image data supplied by the two decoding circuits, and the variations are added to the data of the current frame in order to regenerate the image data of the previous frame.…”

60.2: Dynamic Bit-Rate Allocation of High-Compression Feedforward Driving

“…We have been studying the reduction of image data stored in the frame memory of overdrive for some time. Compression Feedforward Driving (cFFD), which is a second generation overdrive technique, and Motion Adaptive CODEC Feedforward Driving (macFFD), which ranks as the third generation, have been developed and put to practical use before now [7,8].…”