-preset slow bought 0.16%. Ten ffmpeg settings measured on two ARM cores.

The report details the results of encoding tests performed on two distinct video materials using various libx264 settings on a two-core ARM server. The comparison focused on measuring file size, encoding time, and quality using SSIM and PSNR metrics.

On the first, more straightforward material (Material A), which consists of black text on a white background, the veryfast preset achieved a lighter file size (1,873,445 bytes) with a similar quality score (0.999581 SSIM) compared to the medium preset. However, the medium preset on this material fell between the veryfast and slow presets in terms of size and quality. The slower preset did not provide any significant advantage in this case.

In contrast, when evaluating the second, more complex material (Material B), which includes an animated test pattern with temporal noise, the results changed significantly. For this demanding video, the veryfast preset yielded a larger file size (10,709,432 bytes) compared to the medium preset (9,175,052 bytes) at a slightly higher quality (0.914306 SSIM).

The slow preset also showed promise, with a file size 14.3% smaller than the veryfast preset while maintaining a marginally higher quality score (0.916718 SSIM). However, the significant time difference between the veryfast and medium presets (45.30 to 49.53 seconds vs. 29.55 to 32.21 seconds for the medium preset) made the slower option less justifiable.

Overall, the findings suggest that for videos similar to Material A, the medium preset provides a good balance of file size and encoding time. In contrast, for more complex videos like Material B, the medium preset with a higher CRF value (-crf 24) may offer a better trade-off between reduced file size and acceptable quality, despite requiring more encoding time. The slow preset did not provide a significant advantage in this context.