Codec Config OBU (Objective and Subjective) is a syntax used by HEVC (High Efficiency Video Coding), which is an advanced video compression standard. It allows for more efficient encoding of videos, resulting in smaller file sizes without sacrificing image quality. The parameters that can be adjusted to optimize image clarity while maintaining small file sizes include:

1. GOP Size This parameter determines the number of frames between I-frames (intra-coded frames) and P/B-frames (inter-coded frames). A smaller GOP size results in better compression, but may also result in more motion artifacts due to the increased use of interpolation techniques.

2. Bitrate This parameter determines the maximum number of bits that can be used for encoding each frame. Higher bitrates result in higher image quality, but also larger file sizes. Lower bitrates result in smaller file sizes, but may also result in lower image quality due to increased compression artifacts.

3. Quantization Parameter (QP) This parameter determines the amount of quantization that is applied to each pixel value during encoding. Higher QPs result in better compression, but may also result in more visible compression artifacts. Lower QPs result in lower compression and higher image quality.

4. Deblocking Filter Strength (DFS) This parameter determines the strength of the deblocking filter that is applied to each frame during encoding. Higher DFS values result in better compression, but may also result in more visible blocking artifacts due to increased filtering. Lower DFS values result in lower compression and higher image quality.

5. Temporal Filter Strength (TFS) This parameter determines the strength of the temporal filter that is applied to each frame during encoding. Higher TFS values result in better compression, but may also result in more visible motion artifacts due to increased filtering. Lower TFS values result in lower compression and higher image quality.

6. Intra Period (IP) This parameter determines the number of frames between I-frames. A smaller IP results in better compression, but may also result in more visible compression artifacts due to increased use of interpolation techniques.

7. Reference Frame List Length (RFLL) This parameter determines the maximum number of reference frames that can be used for encoding each frame. Higher RFLL values result in better compression, but may also result in more visible motion artifacts due to increased use of interpolation techniques.

8. Slice Height and Width (SHW) These parameters determine the size of each slice during encoding. Smaller SHW values result in better compression, but may also result in more visible compression artifacts due to increased use of interpolation techniques.

9. Entropy Coding Mode (ECM) This parameter determines the entropy coding mode that is used for encoding each frame. Higher ECM values result in better compression, but may also result in more visible compression artifacts due to increased complexity during decoding.

10. Loop Filter Strength (LFS) This parameter determines the strength of the loop filter that is applied to each frame during encoding. Higher LFS values result in better compression, but may also result in more visible blocking and ringing artifacts due to increased filtering. Lower LFS values result in lower compression and higher image quality.

11. Coding Tree Unit (CTU) Size This parameter determines the size of each coding tree unit during encoding. Smaller CTU sizes result in better compression, but may also result in more visible compression artifacts due to increased use of interpolation techniques.