Video Quality Analyzer: frame-by-frame HLS and DASH bitstream analysis

The iReplay.tv Video Quality Analyzer opens a real segment of your HLS or DASH stream and shows where every bit went. One bar per frame, sized by the bits that frame cost and coloured by whether it is an I, P or B frame, the per-frame bitrate view that desktop bitstream analyzers are normally bought for. Beneath the chart sits the actual picture for every frame, so each verdict can be checked by eye rather than taken on trust.

This is no-reference analysis, not VMAF, PSNR or SSIM

VMAF, PSNR and SSIM are full-reference metrics: each one compares an encode against the original master, frame against frame, and none of them can be computed without that master. You do not upload a master here, so this tool reports none of them. What it does instead is read the encoded bitstream itself and explain the structure behind a quality problem. VMAF tells you how good an encode is; this tells you why, and what to change.

What it finds

• Keyframes sitting mid-segment with no scene change behind them, with the waste quantified in KB, kbps and percent of the segment.
• Keyframes correctly placed on a scene cut, which are explicitly not counted as waste: at a hard cut a P frame has almost nothing to predict from and costs nearly as much.
• Scene cuts the encoder could not afford, where rate control ran out of headroom at the exact moment the picture changed.
• IDR versus open-GOP I frames, read at NAL level, and whether B frames are used as references.
• Microbursts over 100, 250, 500 and 1000 ms windows, measured against the BANDWIDTH your manifest declares.
• Gradual transitions such as dissolves and fades, which no scene-cut detector will flag and which are often the most expensive stretch in a segment.
• Frame rate and bitrate the manifest declares against what the media actually contains.

VOD and live are judged differently

The analyzer detects whether the playlist is VOD or live and changes its recommendations accordingly. On VOD a long GOP, open GOP inside segments and a B-pyramid are all free efficiency, and mid-segment keyframes are pure waste. On live the keyframe interval has to be locked to the segment duration and identical across the ladder, B frames cost latency, and the VBV buffer has to be constrained or microbursts reach the player.

It supports HLS with MPEG-TS or fMP4/CMAF segments, DASH with SegmentTemplate, SegmentList or SegmentBase addressing, and direct segment URLs. Analysing the manifest instead of the frames? The Streaming Analyzer checks your encoding ladder, codec profiles, target duration and DRM signalling. This tool was built by Sylvain Corvaisier, a streaming and video engineer with 20 years in the industry. iReplay.tv is run by a collective of streaming and broadcast engineers; you can also hire streaming and broadcast specialists.