For example, common CPU encoders x264 and x265 have a tune parameter which optimizes to objective metrics. You can review the findings here.įurthermore, due to the industry standard of tracking encoder “performance” to quantitative metrics like the ones listed above, many encoders have “taught to the test” that is, they provide different command-line arguments that will give higher scores but may look worse to the human eye. Jan Ozer from the Streaming Media Center posted his experimental correlation of MOS vs the above metrics. Many people will argue which metric is best (although PSNR is commonly considered the least accurate).

Mean Opinion Score (MOS) - Humans visually watching the screen and providing feedback Video Multimethod Assessment Fusion (VMAF) Structural Similarity Index Metric (SSIM) This has led to an evolution of algorithmic solutions, the most common of which are: There has been a longstanding goal for video engineers to quantitatively determine the output quality of an encoder without having to watch and inspect every individual frame.

Ffmpeg compress video bit rate