# Effect of Saturation Arithmetic on Sum of Absolute Difference (SAD) Computation in H.264 - PowerPoint PPT Presentation

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Effect of Saturation Arithmetic on Sum of Absolute Difference (SAD) Computation in H.264. Venkata Suman Sanikommu ECE 734 Project Presentation. Motion Estimation. Block matching between successive frames – video compression Find the best matching block (Motion Vector)

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Effect of Saturation Arithmetic on Sum of Absolute Difference (SAD) Computation in H.264

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## Effect of Saturation Arithmetic on Sum of Absolute Difference (SAD) Computation in H.264

Venkata Suman Sanikommu

ECE 734 Project Presentation

### Motion Estimation

• Block matching between successive frames – video compression

• Find the best matching block (Motion Vector)

• Motion vector will be used to reproduce the reference frame

• Motion vectors are found by calculating minimum SAD

• Compute (Ai – Bi) for all 16 x 16 pixels in the two blocks A and B

• Determine which Ai – Bi is less than zero and produce the absolute value in that case, else produce Ai – Bi

• Perform accumulate operation to all 16x16 absolute values.

### Saturation Arithmetic

• Overflowed values will be represented as maximum values

• Unsigned: 00…0h, FF…Fh

• Example:

• 6234h + E123h => FFFFh (saturated)

### Saturation Arithmetic – SAD [1]

• Use saturation arithmetic and limit the number of bits used to represent SAD values

• Reduced computation complexity

• Might affect the quality of block matching and thus motion estimation

### Saturation Arithmetic – SAD [2]

• If min{SAD} is less than FF…Fh

• Does not affect motion estimation

• If min{SAD} is greater than FF…Fh

• Affects motion estimation

• Subset size for block matching increases

• Increased encoded file size

• We have to randomly select one for motion estimation

• Randomly selected block might not be a best match

### Project Work

• Modify H.264 SAD computation code for saturation arithmetic

• Compare the performance of H.264 video coding for modular arithmetic and Saturation arithmetic for different number of bits.

• What is the minimum number of bits required to successfully use saturation arithmetic?

• How frequently does the SAD value saturate for a given number of bits to represent?

• What is the effect of saturation on encoded file size?