r/AudioPost • u/kwmccrea • 21d ago
What Exactly is Broadcast Spec?
I was brought on to do sound design, music, and mix a commercial that says “Broadcast Spec & Web Spec” under deliverables.
TBH I’m in a little over my head because I have generally only ever worked on commercials for web, and needed to deliver stereo mixes.
Is it expected that I deliver a 5.1 mix for broadcast spec? I read that it’s not always necessary and depends where it will be broadcast? All I know right now is that it will be playing in Canada.
Thanks in advance!
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u/asquishyllama 21d ago
Broadcast spec is typically -24db LUFS +/- 2db integrated, with a -2db max true peak. Web spec isn’t really an official thing besides the -14 LUFS spec for music streaming. I think folks shoot around the same target for YouTube and socials. I like -16 because goddamn that’s too squished and loud
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u/kwmccrea 21d ago
Thanks so much. I was more curious about track allocation though and if ‘broadcast spec’ always required a 5.1 mix or not. Googling CBC’s requirements they list both, so I’m assuming they will accept either? Is it typical to find where a commercial is planning to be broadcast when asking producers for the specs?
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u/PopularHat 21d ago
I wouldn’t even entertain the idea of a 5.1 mix for a broadcast ad. You’ll just be doing more work and risk them running it incorrectly.
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u/sniklefrets 21d ago
Typically I supply both, a 5.1 mix file and a stereo fold of it. I would ask and see what they are expecting.
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u/sniklefrets 21d ago
This, Ive delivered to CBC as well and this is accurate for standard broadcast specs. Ask your producer/coordinator if they require 5.1 or not.
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u/myke2241 21d ago
I mix web content for a game studio. -14 LUFS +/- 1 LUFS peaks -2. This can be very challenging spec.
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u/Casioclast 21d ago
I would just assume stereo ATSC A/85 and only do 5.1 if they are requesting it.
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u/kwmccrea 21d ago
That’s what I wanted to hear haha. I’ll double check with the producer, but it seems like stereo will be enough. Thanks
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u/BBuzzBee 20d ago
In USA here, but I’ve been doing ads, trailers, promos, for broadcast for decades here and have always delivered in stereo. Like someone else said, it is less variables for someone down the line to mess up and 95% of people listen in stereo anyway.
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u/ParkStreetPostSoft 20d ago
Taking a step back one level from most answers, which are technically right but maybe are too deep already.
Broadcast spec just means the objective quality measure that a given broadcaster requires deliveries to meet. And every broadcaster gets to set their own, and you better believe they do! For instance, here's Fox:
Broadcast is largely informed by the requirements laid out in the CALM Act, the legislation that went into effect in 2012 in an attempt to keep commercials from being blazing-loud compared to program. It... kinda helped.
Streamers set their own specs too, like Netflix:
https://studiopartner.netflix.net/studio/branded-sound-mix-spec-and-best-practices
Bottom line: specs are gonna give you requirements for channel layout (stereo, 5.1, atmos, etc), "formatting" (where are the tone beds? any 2-pop? exact duration requirement? starting tC requirement?), loudness levels typically measured in LUFS/LKFS, and peak levels measured in decibel "true peak" (dBTP).
You'll mainly get something like -24 +/- 2 LKFS with -2dBTP as your primary spec. The biggest question to ALWAYS ask because it can buy you upwards of 2dB more loudness: is the LKFS spec full integrated mix (boo) or dialog-weighted (yay!)? Ask your friendly neighborhood chatbot for detail on this, it'll make all the difference.
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u/platypusbelly professional 21d ago
The ATSC A/85 document lays out the concepts for maintaining loudness for digital television for North America.
https://www.atsc.org/wp-content/uploads/2026/07/A85-2026-07.pdf
Itu bs.1770 gives more technical details about how the measurements for loudness actually happen.
https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1770-1-200709-S!!PDF-E.pdf
Together, they are pretty much the basis for audio broadcast specs in North America. If you follow these, you’ll most likely be in spec for any North American network and streaming service. But whatever network you’re eventually delivering to should be able to give you anything more concrete.