Stability score
A stability score measures how smoothly a video played once it started. It is built from how many times playback paused to buffer and how much of the viewing time those pauses took up. A high score means the picture kept moving; a low score means viewers sat through spinners.
Why it matters
Stalls are the playback problem viewers notice most and forgive least. A falling stability score is an early warning that viewers are sitting through spinners, which leads to shorter sessions, fewer ad impressions and more cancellations. Tracking it by region and network shows where delivery is failing.
How it works
- The player logs every time playback pauses to refill its buffer after the video has started.
- It records both how many pauses happened and how long they lasted in total.
- These become buffer frequency and buffer ratio, which compare stalls with the time spent watching.
- Fewer and shorter stalls push the score toward the top; frequent or long stalls pull it down.
What causes a low stability score?
A low stability score is usually caused by the network or CDN failing to deliver video as fast as it plays. Common reasons are a bitrate ladder whose lowest rung is too high for mobile networks, an overloaded CDN edge in one region, weak home Wi-Fi, or a player that switches quality too slowly. Breaking the score down by ISP, CDN and device usually points to the cause. With FastPix Video Data, your team can see which ISP, CDN or device is behind a drop in one place, because it captures 56 dimensions per session.
Why does my video keep buffering?
Video keeps buffering when the player downloads data more slowly than it plays it, so the buffer runs empty. The network may be too slow for the chosen quality, the CDN edge may be distant or busy, or the player may hold a high rendition too long. Adding lower renditions, checking CDN performance by region and tuning the player's switching logic are the usual fixes.
Where it's used
Live sports streamers and OTT services watch the stability score by region and ISP, because a drop in one area usually means a delivery problem that is costing them viewers right now.
Where it usually goes wrong, and how FastPix handles it
Teams often track total buffering time alone, which hides the difference between one long stall and many short ones, and platform-wide averages hide regional problems.
Buffer count and buffer ratio feed the stability score that FastPix Video Data calculates for every view. It is the largest part of the QoE score and can be broken down by country, ISP, CDN, device and other dimensions. The region or network where viewers stall becomes obvious, so delivery there gets fixed before those viewers cancel.
By the numbers
- A 2012 study of online video viewers found that a viewer whose video froze for 1 percent of its duration watched 5 percent fewer minutes than a comparable viewer whose video did not freeze. (Research quantifies how video stream quality affects viewer behavior (ScienceDaily, 2012))
