TH45340B - Method of simulating film grain based on pre-calculated conversion coefficient. - Google Patents

Abstract

DC60 The film grain simulation inside the receiver (11) is performed by first acquiring at least one block of pre-computed transform coefficients. The block of pre-computed transform coefficients is filtered to a frequency range characterized by the desired film grain pattern. In practice, the frequency range lies within the set of cutoff frequencies fHL, fVL, fHH, and fVH of the two-dimensional filter circuit, where the desired film grain pattern is characterized. The filtered set of coefficients is then inversely transformed to obtain the film grain pattern. The film grain simulation inside the receiver (11) is performed by first acquiring at least one block of pre-computed transform coefficients. The block of pre-computed transform coefficients is filtered to a frequency range characterized by the desired film grain pattern. In practice, the frequency range lies within the set of cutoff frequencies fHL, fVL, fHH, and fVH of the two-dimensional filter circuit, where the desired film grain pattern is characterized. The filtered set of coefficients is then inversely transformed to obtain the film grain pattern.

Claims (5)

A method for generating a block of film, comprising the steps of (a) obtaining a pre-computed block of transformed coefficients, (b) frequency-filtering the transformed coefficients corresponding to a frequency range characterized by a desired film grain pattern, and (c) performing an inverse transformation on the frequency-filtered transformed coefficients. 2. The method according to claim 1, wherein the step of obtaining the pre-computed block of transformed coefficients comprises the further step of reading at least one pre-computed block of transformed coefficients from memory. 3. The method according to claim 1, wherein the step of frequency-filtering comprises the further step of filtering the transformed coefficients corresponding to a set of cutoff frequencies fHL, fVL, fHH and fVH of the two-dimensional filter circuit, wherein the characteristic of the desired film grain pattern is characterized. 4. The method according to claim 1, wherein the step of performing the transformed coefficients The inverse transformation further comprises the step of performing the inverse discrete cosine transform. 5. The method according to claim 1 further comprises the step of scaling the inversely transformed blocks of coefficients. 6. The method according to claim 1, wherein steps (b) and (c) are repeated for all possible grain sizes and shapes to obtain a plurality of grain patterns, each derived from a pre-computed block of transformed coefficients. 7. The method according to claim 1, wherein steps (a), (b), and (c) are repeated for all possible grain sizes and shapes to obtain a plurality of grain patterns, each derived from a pre-computed block of transformed coefficients. 8. The method according to claim 6 further comprises the step of storing each inversely transformed set of filtered coefficients in memory during the repeated operation. Each of step (c) 9. The method according to claim 7 further comprises the step of storing each inversely transformed set of filtered coefficients in memory during the iterated operation, each of step (c) 1 0. The method according to claim 1 further comprises the step of scaling the inversely transformed set of filtered coefficients before the coefficients undergo the inverse transformation 1. 1. The apparatus comprises a memory for storing at least one pre-computed block of transformed coefficients, at least one processor of a programmed processor, and dedicated logic circuits for simulating film grains by (a) obtaining the pre-computed block of transformed coefficients from the memory, (b) filtering the transformed coefficients to a frequency range which is characterized by a desired shape of the film grains, and (c) performing an inverse transformation on the transformed coefficients which are filtered to a frequency range. 2. The device according to claim 11, wherein at least one processor of the programmed processor and the dedicated logic circuit further scales the converted coefficients that are inversely frequency filtered. 3. The apparatus according to claim 11 further comprises a second memory for storing the inversely filtered transformed coefficients 1 4. The apparatus further comprises a first memory for storing at least one pre-computed block of transformed coefficients, a means for obtaining the pre-computed block of transformed coefficients from the memory, a means for filtering the transformed coefficients that respond to a frequency range characterized by a desired grain pattern, and a means for performing an inverse transformation on the transformed coefficients that are filtered 1 . 4. The apparatus according to claim 14 further comprises a means for making the converted coefficient scale that is inversely frequency-transformed filtered 1. 5. The apparatus according to claim 14 further comprising a second memory unit for storing the converted coefficients that are filtered and the inversely converted frequency.