Video surround channel standards

[Matt Marcus]

Speak to me of standards for 5.1-7.1 audio channels in video files. I'm finding myself having to navigate this more and more as one of our university venues is now also a screening facility. It seems to be the wild west out there.
Additionally, we tend to do the screenings through QLab so we can have a more professional presentation w/ preshow slides and the like. QLab is transposing the LFE and Ctr channels in many provided files. Doing the obvious fix w/ the matrix mixer. Everything will route natively through the system (Connectivity into a Qsys core is HDMI) when playing a file through Quicktime.

[micpool]

There is only one standard, the SMPTE one. However there are several other channel orders that are not published  standards in common everyday use. Generally if you open a file in Quicktime  player and get info, the audio tab will state the channel order.

There is still no guarantee that the channels were accurately labelled or routed in the first place.

The matrix is a very handy tool for sorting out these routing problems.

5.1 can generally be deduced by looking at the waveforms while playing back, but the higher channel count formats are not so easy.

I don’t think QLab is transposing any channels, the audio files just haven’t been interleaved  in the correct order.

Mic

[Matt Marcus]

Thanks Mic-

Yup- All of that- I've obviously been using the matrix to compensate, but also the output patch Patch Routing tab is handy for this. 

I've found out there it a FILM standard as well. Here they are in 5.1:

SMPTE=L/C/R/Ls/Rs/LFE

FILM=L/R/C/LFE/Ls/Rs

The FILM ordering is how the majority of screening files from filmmakers have been being delivered.

Also an oddity-  the Dolby originating 7.1 test file we've been using only shows up as 6 channels in QLab- even though all 8 channels are visible when opening the file in an editor (Ocenaudio in this case). The side and rear Chanels get combined, somehow. Also interestingly, using the excellent little file converter Permute, I've been able to create versions of the file from which QLab separates out all 8 channels.

Upon further investigation the  channel transposition looks like it's happening at the OS level in Audio Setup, Doesn't seem to be a way to change this, but still digging.

[Philip Perkins]

We do audio post for films for theatrical and festivals all the time for the last few decades, and the channel order for 5.1 delivery has never been other than “film” or L/R/C/LFE/Ls/Rs.

phil p

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[micpool]

I think there is a difference between standards and conventions.

The SMPTE/ITU FORMAT is a formal standard. Film order is an alternative convention, like pin3 hot on an XLR, but it’s debatable if it is a true standard the  strict use of the term.

Regarding the 7.1 files you believe  QLab is misinterpreting….

If you open these in Quicktime player, how many audio tracks (not channels) are listed. Could you post a, creenshot of the get info window, with the disclosure  triangle on the audio info opened.

QLab will only ever read the first of a maximum of 24 audio tracks each of which , could theoretically  have up to  32 multiplexed audio channels.

Mic

[micpool]

On Saturday, March 14, 2026 at 11:54:31 PM UTC philip....@linesballet.org wrote:

We do audio post for films for theatrical and festivals all the time for the last few decades, and the channel order for 5.1 delivery has never been other than “film” or L/R/C/LFE/Ls/Rs.

I think you will find that that is the SMPTE order. Film formats always,have C as ch2 

[Philip Perkins]

The standard we follow for 5.1 is the one something like 99.9% of our clients over the past 20 years (since we started delivering in 5.1) have demanded on their spec sheets: L/R/C/LFE/Ls/Rs.   This has been for theatrical, festivals, streaming, broadcast and special venue.

phil p

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[micpool]

On Saturday, March 14, 2026 at 11:18:27 PM UTC Matt Marcus wrote:. 

I've found out there it a FILM standard as well. Here they are in 5.1:

SMPTE=L/C/R/Ls/Rs/LFE

FILM=L/R/C/LFE/Ls/Rs

I think you have got that back to front. Can you provide a ,link to your reference? 

Film format always has C as Ch2.

[Kinetic Screen]

For what it's worth, the grouping L/R  C/LFE  Ls/Rs is also the way that PCs and similar sources have been handling 5.1 for years...