The DiffALL Blog
Practical guides on image and video quality metrics, compression, and media comparison workflows.
How to Check Video Quality When You Don't Have the Original
SSIM, PSNR and VMAF all need a reference file. What can still be measured from one video on its own — bitrate, focus, blocking, freezes — and what cannot.
Audio QualityIs My Audio Clipping? How to Tell Loud From Damaged
Clipping and loudness look identical on a peak meter. The measurement that separates them is the length of the flat run at the top — here is how to read it.
Image QualityIs This Photo Out of Focus, or Is It Just Small?
Why a photo looks sharp on a phone and soft on a monitor, what focus is as a measurable number, and how to check one image with no sharp copy to compare to.
Image QualityIs This Photo Good Enough to Print?
Megapixels are the least important thing on the list. What really decides whether a photo survives print, and how to check before you pay for it.
Audio QualityLUFS Explained: How Loud Should Your Audio Actually Be?
Why peak meters do not measure loudness, what BS.1770 does instead, every streaming platform's target, and the bug in most loudness code.
QA & TestingNo-Reference Quality Metrics: Judging a File With Nothing to Compare It To
SSIM and VMAF need the original. What changes with only one file, which questions stay answerable, and why one averaged score hides the defect that matters.
Audio QualityWhat MP3 Bitrate Should I Use? Balancing Quality and File Size
Measured numbers for where MP3 stops discarding audible content, why AAC and Opus need fewer kbps, and how to check what a file is really carrying.
Video QualityWhy Does My Video Look Blocky? Diagnosing Compression Artefacts
Blocking, banding, mosquito noise and smearing have four different causes and four different fixes. How to tell which one you are looking at.
Audio QualityCBR or VBR: Is That Bitrate a Promise or an Average?
CBR vs VBR: the same '192 kbps' means two different things. How to tell which your file is, why it changes what the number is worth, and when to use each.
Video QAHow to Find a Frozen Frame Without Watching the Whole Video
A freeze, a dropped frame and a deliberate hold look alike when you scrub. How to find them from the file itself in a fraction of a second, with no decoding.
Image QualityWhat JPEG Quality Was This Saved At? The File Already Knows
A JPEG records its quality setting in its quantisation tables. How to read it back, why re-saving loses more than you expect, and what the number cannot say.
Image QualityYour Photo's Own Metadata Explains Why It Looks Wrong
Noise, softness, colours that shift, photos that appear sideways: the cause is usually in the file's EXIF header. What metadata answers that pixels cannot.