Audio track layout verifier

EBU R123 and R48 track layouts

A master whose tracks don’t match the delivery’s track sheet is one of the commonest rejects. Drop the file, pick the EBU R123 or R48 layout, and see every channel against what’s expected: silent or near-silent tracks, dual mono, one-sided or inverted pairs, the stereo copied into the M&E, Dolby E in the wrong place, and a 5.1 in film order. It reads in your browser. Nothing is uploaded.

Drop a master here

MXF, MOV, MP4, WAV and AIFF at any size: only the audio is read. Other containers are listed but not checked. Checked in your browser; nothing is uploaded.

Check against

What the file says, and what it contains

Two separate readings, because they disagree often and the disagreement is the finding. The headers give the tracks, their channel counts, coding, sample rate and bit depth, and the channel labels the file carries: the ‘chan’ atom in a MOV, SMPTE ST 377-4 MCA labels in an MXF. Then every track is decoded once and each channel’s content checked. Channels are numbered across the file, A1 upwards, the way R123 and R48 number them and a track sheet lists them, whether the master holds one 8-channel track or eight mono tracks.

The checks

Track count, short or long. Channels the layout has no slot for are reported, never ignored.
Pairs split across tracks that also carry other channels, where a player or QC tool won’t read them as one pair.
Silence. Digital silence (every sample zero, what “PCM silence” in a spec means) is kept apart from very low level: hiss, dither or bleed on a track someone forgot to mute.
Pairs: dual mono, one side only, and opposite polarity, with the times when it only happens in places.
Copies: a channel or pair that carries the same audio as another, such as the stereo mix copied into the M&E tracks, bit for bit or at another level. Surrounds that are the fronts of the same 5.1 turned down are a warning instead: that’s an upmix, not a wrong track.
Dolby E and other SMPTE ST 337 data in AES pairs: where it is, against where the layout wants encoded audio, its word size and frame rate. It’s reported as data and never measured as sound.
Labels that contradict the layout, and format against R123’s general note: “Audio should be 48 kHz, 24 bit, and time-aligned with picture on tape, file, connection or link.”

5.1 order is a guess, and says so

Broadcast order is L R C LFE Ls Rs (SMPTE, EBU R123 and R48); film and Pro Tools sessions use L C R Ls Rs LFE. Laid down in the wrong one, centre and LFE land on the surrounds. Nothing in the file says which it is, so the tool looks for the LFE: the one channel with almost no energy above 120 Hz, ten seconds at a time. Where that channel sits says the order; whether the surrounds follow their own side backs it up or weakens it. The result is “very likely”, “likely” or “can’t tell”, never certain. A silent LFE, or a passage where nothing is band-limited, can’t decide it and says so.

Thresholds are ours

No standard publishes a figure for “this channel is silent”, “these two channels are the same” or “this is the LFE”, so these are the tool’s own, set with margin and tested on real masters: very low level is a channel that never goes above −60 dBFS; a silent stretch lasts at least 10 s; two channels are copies at a correlation of 0.98 or more; the LFE has under 3% of its energy above 120 Hz and no more than 1/3 of any other channel’s share.

Sources

EBU R 123 (2009), Audio Track Allocation for File Exchange: Table 1 layouts, general notes, §4 Dolby E capacity (6 channels at 16-bit, 8 at 20-bit). tech.ebu.ch (PDF), checked 2026-10-13.
EBU R 48 (2005), Allocation of audio tracks on digital television recorders: Table 1. tech.ebu.ch (PDF), checked 2026-10-13.
SMPTE ST 337:2015 (burst preamble and burst_info), ST 338:2016 (data types), RDD 33:2015 (Dolby E: data type 28, one burst per video frame, burst spacing per frame rate). Checked 2026-10-13. Dolby E’s own programme configuration isn’t read: no published standard describes the inside of its frame.
SMPTE ST 377-4:2021, MCA labelling in MXF. Checked 2026-10-13.

A broadcaster’s track sheet adds its own channel counts and rules for unused tracks. The track layouts page shows some broadcasters’ published allocations for reference.