Segment timing checker

Black, silence, parts and breaks

Drop the master and this finds its black and its silence to the frame, builds the head, parts, breaks and tail from them, and compares them with your timing sheet (or the file’s own AS-11 segmentation). It runs in your browser: the master is read in place, however large, and nothing is uploaded.

Drop a master here

MXF or MOV: ProRes, DNxHD/HR, XDCAM (MPEG-2), AVC-Intra and other H.264, HEVC, JPEG 2000. Any size: the file is read in place, in your browser, and nothing is uploaded.

Programme starts at

Anything before it (bars, tone, clock) is the head, not part 1. Leave it empty if the programme starts on the first frame.

Timing sheet (optional)

Paste or type rows. An AS-11 file’s own segmentation is used when this is empty.

How breaks are read

A break is silence with black in it. In a typical hard-parted master the sound stops on a part’s end point and the picture may hold for a few seconds before it goes to black; then perhaps a clock, more black, and the next part. So a part ends where its sound stops, not where the black starts, and the next starts where the silence ends. Black with sound under it and silence over picture aren’t breaks: they’re reported as findings, with sound that runs into the black or starts before the picture, and black flashes and dropouts too short to count.

Bars and tone, and a slate with sound, look like programme to black and silence, so anything that ends before the programme start you set (10:00:00:00 unless you change it) is the head. After the last part, material that follows a gap of 80 s or more (textless elements, say) is the tail: breaks between parts can run past a minute, so a shorter gap can’t tell them apart, and the comparison with the sheet will show it as an extra part.

The picture: decoded, or said not to be

No browser decodes ProRes, DNx, XDCAM or JPEG 2000 itself, so the page carries its own decoder: FFmpeg’s (LGPL), built for the browser with only the decoders and the MOV and MXF readers in it (under 1 MB to download). On a page that allows it, it uses several threads: a 52-minute ProRes HQ master takes about 4 minutes, a 90-minute XDCAM master about 6. For ProRes, DNx and JPEG 2000 it decodes every few frames, then every frame around each edge, so edges land on the exact frame. The report says which route checked the picture, and how many frames it decoded.

Frame sizes give a first look in seconds while the decoding runs: black compresses small. They’re only candidates (frames at or below 0.1× the file’s median size), never findings: a flat grey card compresses small too, noisy black doesn’t, and DNx and AVC-Intra frames are all the same size.

Thresholds are ours

No broadcaster publishes a level or a length for “black” or “silence”, so these are the tool’s own, set on real masters. Black: a 4×4 block of picture at or below 1% of the range above black (Y′ 18 in 8-bit limited range), in 98% of the frame, for at least 0.5 s. ffmpeg’s blackdetect allows 10%, and at 10% a dark night scene is black. Silence: every sample below −70 dBFS for at least 0.5 s; digital silence (every sample zero) is reported apart. Room tone at −60 dBFS is not silence. Picture and sound edges more than 1 frame apart are reported.

Sources

AMWA AS-11 X1, Program Segmentation Track and DM_AS_11_Segmentation: One Program Segmentation Track in the Material Package: a DM Segment per programme part (AS_11_Part_Number, AS_11_Part_Total), Filler for non-programme content ("black, ident, clock"). SOM/EOM come from where each segment sits against the Material Package timecode. checked 2026-10-13.