Adaptive interlace-to-progressive scan conversion algorithm

An interlace-to-progressive scan conversion system, comprising:

• a spatial line averaging prefilter having a prefiltered signal as an output;
• a motion estimator having the prefiltered signal as input and a motion-corrected signal as an output, the motion estimator comprising:
• a 3-D recursive search sub-component;
• a motion vector correction sub-component;
• a block erosion sub-component;
• a three-stage adaptive recursive filter, wherein:
• a first stage comprises a function that selects between using static pixels data and moving pixels data from a next field;
• a second stage comprises a function that selects a more valid set of data between motion compensated data from a previous field and the pixels selected by the first stage;
• and
• a third stage comprises a function that combines an intra-field interpolation with the more valid set of data selected by the second stage.

An interlace-to-progressive scan conversion system, comprising:

• a spatial line averaging prefilter having a prefiltered signal as an output;
• a motion estimator having the prefiltered signal as input and a motion-corrected signal as an output, the motion estimator comprising:
• a 3-D recursive search sub-component having a bilinear interpolator;
• a motion vector correction sub-component having an error function, the error function including penalties related to a length of the difference vector between a given candidate vector and a plurality of neighboring vectors;
• a block erosion sub-component;
• wherein the motion estimator assumes that a motion vector for an object between a previous field and a current field is the same as a motion vector for the object between the current field and a next field
• a three-stage adaptive recursive filter having the prefiltered output and the motion-corrected output as inputs, the three stages comprising:
• a first stage that comprises a function that selects between using static pixels data and moving pixels data from a next field;
• a second stage that comprises a function that selects a more valid set of data between motion compensated data from a previous field and the pixels selected by the first stage;
• and
• a third stage that comprises a function that combines an intra-field interpolation with the more valid set of data selected by the second stage.

An interlace-to-progressive scan conversion system, comprising:

• a spatial line averaging prefilter having a prefiltered signal as an output;
• a motion estimator having the prefiltered signal as input and a motion-corrected signal as an output, the motion estimator comprising:
• a 3-D recursive search sub-component;
• a motion vector correction sub-component;
• and a block erosion sub-component;
• wherein:
• the 3-D recursive search sub-component includes a bilinear interpolator defined by:
• 53 F ⁡ ( x , y , t ) = ⁢ ( yf · xf · F ⁡ ( xi , yi , t ) ) + ( yf · ( 1 - xf ) · F ⁡ ( xi + 1 , yi , t ) ) + ⁢ ( ( 1 - yf ) · xf · F ⁡ ( xi , yi + 1 , t ) ) + ( ( 1 - yf ) · ( 1 - xf ) · ⁢ F ⁡ ( xi + 1 , yi + 1 , t ) ⁢ where :
• ⁢ yf = ⌊ y ⌋ ⁢ ⁢ xf = ⌊ x ⌋ ⁢ and :
• ⁢ yi = y - ⌊ y ⌋ ⁢ ⁢ xi = x - ⌊ x ⌋
• and wherein a value of a first estimator is set to a value of a second estimator if:
• e({overscore (MV)}a,{overscore (X)}−{overscore (SMV)}a,t)>e({overscore (MV)}b,{overscore (X)}−{overscore (SMV)}b,t)+Th
• and wherein the value of the second estimator is set to the value of the first estimator if:
• e({overscore (MV)}b,{overscore (X)}−{overscore (SMV)}b,t)>e({overscore (MV)}a,{overscore (X)}−{overscore (SMV)}a,t)+Th
• where Th is a fixed threshold;
• the 3-D recursive search sub-component has a look-up table consisting of:
• 54 US n = { ( 0 0 ) , ( 0 1 ) , ( 0 - 1 ) , ( 1 0 ) , ( - 1 0 ) , ( 0 2 ) , ( 0 - 2 ) , ( 3 0 ) , ( - 3 0 ) , ( 0 1 4 ) , ( 0 - 1 4 ) , ( 1 4 0 ) , ( - 1 4 0 ) }
• a motion vector correction sub-component having an motion vector error correction function defined by:
• 55 MV _ ⁡ ( x , y , t ) = { ⁢ ( 0 0 ) , ( e m ⁡ ( x , y , t ) ≥ e s ⁡ ( x , y , t ) ) ⁢ MV _ ⁢ ( x , y , t ) , ( e m ⁡ ( x , y , t ) < e s ⁡ ( x , y , t ) ) ⁢ ⁢ where :
• ⁢ e m ⁡ ( x , y , t ) = ∑ [LeftBracketingBar] F ⁡ ( C ) - F ⁡ ( D ) [RightBracketingBar] ⁢ ⁢ e s ⁡ ( x , y , t ) = ∑ [LeftBracketingBar] F ⁡ ( A ) - F ⁡ ( B ) [RightBracketingBar] ⁢
• and where A, B, C, D, and X are blocks containing ends of candidate motion vectors, X being in the current field, A and C being in the previous field, and B and D being in the next field.
• a block erosion sub-component that divides each block according to:
• B(x,y,t)={(x,y)|Xx−X/2≦x≦Xx+X/2Xy−Y/2≦y≦Xy+Y/2}
• wherein a vector {overscore (MV)}(x,y,t) is assigned, into four sub-blocks Bi,j(x , y , t)
• 56 B i , j ⁢ ( x , y , t ) = { ( x , y ) ❘ X x - ( 1 - i ) · X 4 ≤ x ≤ X x + ( 1 + i ) · X 4 ⋀ X y ⁢ ( 1 - j ) · Y 4 ≤ y ≤ X y + ( 1 + j ) · Y 4 }
• and wherein the variables I and j take the values +1 and −1;
• wherein a vector MVij(x, y, t) is assigned to the pixels of each of the sub-blocks Bij(x, y, t):
• ∀(x,y)εBi,j(x,y,t):{overscore (MV)}i,j(x,y,t)=:{overscore (MV)}i,j({overscore (X)},t)
• wherein:
• {overscore (MV)}i,j({overscore (X)},t)=med[{overscore (MV)}(x+i·X,y,t),{overscore (MV)}({overscore (X)},t), {overscore (MV)}(x,y+j·Y,t)]
• wherein the median function is a median on the x and y vector components separately;
• and wherein a resulting vector is replaced by an original motion vector unless the resulting vector is equal to one of the three input vectors.
• a three-stage adaptive recursive filter having the prefiltered signal and motion-corrected signals as output, the three stages comprising:
• a first stage comprises a function that selects between using static pixels data and moving pixels data from a next field according to the function:
• 57 F n ⁡ ( x , y , t ) = { ⁢ F ⁡ ( x + MV x ⁡ ( x , y , t ) , y + MV y ⁡ ( x , y , t ) , t + 1 ) , ( D m < D s ) ⁢ F ⁡ ( x , y , t + 1 ) , ( D m ≥ D s ) ⁢ ⁢ where :
• ⁢ ⁢ D s = ∑ k = - 2 2 ⁢ C v ⁡ ( k ) · [LeftBracketingBar] F ⁡ ( x , y + k , t ) - F ⁡ ( x , y + k , t + 1 ) [RightBracketingBar] ⁢ ⁢ ⁢ D m = ∑ k = - 2 2 ⁢ C v ⁡ ( k ) · [LeftBracketingBar] F ⁡ ( x , y + k , t ) - F ⁡ ( x - MV x ⁡ ( x , y , t ) , y - MV y ⁡ ( x , y , t ) + k , t + 1 ) [RightBracketingBar]
• a second stage comprises a function that selects a more valid set of data between motion compensated data from a previous field and the pixels selected by the first stage;
• and
• a third stage comprises a function that combines an intra-field interpolation with the more valid set of data selected by the second stage according to the function:
• 58 F o ⁡ ( x , y , t ) = { ⁢ F ⁡ ( x , y , t ) , ( y ⁢ ⁢ mod ⁢ ⁢ 2 = t ⁢ ⁢ mod ⁢ ⁢ 2 ) ⁢ ⁢ ( c i · F i ⁡ ( x , y , t ) ) + ( 1 - c i ) ⁢ ( c p · F p ⁡ ( x , y , t ) + ( 1 - c p ) ⁢ F n ⁡ ( x , y , t ) ) , ( otherwise ) ⁢
• wherein ci and cp are adaptive coefficients ranging from 0 to 1;
• Fn is given by:
• 59 F n ⁡ ( x , y , t ) = { ⁢ F ⁡ ( x + MV x ⁡ ( x , y , t ) , y + MV y ⁡ ( x , y , t ) , t + 1 ) , ( D m < D s ) ⁢ F ⁡ ( x , y , t + 1 ) , ( D m ≥ D s )
• wherein intra-field interpolation is given by:
• 60 F i ⁢ ( x , y , t ) = F ⁢ ( x , y - 1 , t ) + F ⁢ ( x , y + 1 , t ) 2
• and wherein backward data prediction is given by:
• Fp(x,y,t)=F(x−MVx(x,y,t),y−MVy(x,y,t),t−1)

A method for converting an interlaced image to a progressive scan image, the method comprsing:

• providing an input signal corresponding to an image;
• prefiltering the input signal with a spatial line averaging prefilter;
• estimating motion in the image by:
• performing a 3-D recursive search;
• performing a motion vector correction;
• performing a block erosion to reduce blockiness in the progressive scan image;
• filtering the signal in three stages:
• in the first stage selecting between using static pixels data and moving pixels data from a next field;
• in the second stage selecting a more valid set of data between motion compensated data from a previous field and the pixels selected by the first stage;
• and
• in the third stage combining an intra-field interpolation with the more valid set of data selected by the second stage.

A method for converting an interlaced image to a progressive scan image, the method comprsing:

• providing an input signal corresponding to an image;
• prefiltering the input signal with a spatial line averaging prefilter;
• estimating motion in the image by:
• assuming that a motion vector for an object between a previous field and a current field is the same as a motion vector for the object between the current field and a next field;
• performing a 3-D recursive search;
• performing a motion vector correction in which the error function penalizes a candidate vector based on a length of a difference vector between the candidate vector and a plurality of neighboring vectors;
• performing a block erosion to reduce blockiness in the progressive scan image;
• filtering the signal in three stages:
• in the first stage selecting between using static pixels data and moving pixels data from a next field;
• in the second stage selecting a more valid set of data between motion compensated data from a previous field and the pixels selected by the first stage;
• and
• in the third stage combining an intra-field interpolation with the more valid set of data selected by the second stage.