Audio compression of a broadcast TV signal causing problems?
August 5, 2014 11:55 AM   Subscribe

Two of the broadcast channels in my area (think lower mid-market) have some serious audio issues described after the jump. Is it amateurish compression?

The local NBC channel goes weird mostly during sports broadcasts, where the play-by-play and color commentary (but not the ambient crowd noise, etc.) fades in and out. This isn't a complete fade-out, but more like someone turning the volume from 3 to 7 every 1.5 seconds. This was especially evident in the Stanley Cup playoffs, where Doc Emerick sounded like he was waving his mike back and forth in front of him.

The local CBS channel seems to turn up the gain on certain audio tracks. I've especially noticed this during any hour-long cop procedural (Criminal Minds). The background music and sound effects are at a fairly normal volume, but the dialogue is dialed back about 50%. So I turn it up to hear the dialogue, but then the gunshots/moody strings pad/whatever is nearly deafening.

Now, I do not notice these problems with the station's own audio broadcast (i.e., local news, etc.)

What little I know about audio compression leads me to believe that each station has squashed the audio mix somehow with a compressor, leading to these problems. Obviously, these are small-time markets and perhaps they can't afford to hire the best audio engineers. Is this a case of amateurish compression?
posted by kuanes to Media & Arts (8 answers total)
Are you getting these broadcasts via an OTA antenna? Or are you watching them via cable or satellite?

If the former, then yes, it could be the local station. If the latter, then it could be the local station or it could be the compression that your carrier uses to pass that signal on to you.

If you have cable and On Demand, then watch an episode of something that you know had a problem and compare.
posted by inturnaround at 12:07 PM on August 5, 2014

Response by poster: Sorry, should have mentioned it is via cable, not OTA.

I have not noticed this problem on any other channel, but it is pronounced on these two broadcast channels.
posted by kuanes at 12:10 PM on August 5, 2014

Yeah, it sounds like bad dynamic range compression.
posted by destructive cactus at 12:20 PM on August 5, 2014

This almost sounds like a phasing problem with stereo sound (if the two channels are out of phase, things that appear only on one or the other channel sound fine, things that appear in the center of the sound field are muted because the out-of-phase sounds on the two channels cancel each other out). Or maybe do you use a center-channel speaker that isn't set up right, or an amplifier that is expecting a center channel speaker that isn't there?
posted by BillMcMurdo at 1:00 PM on August 5, 2014 [1 favorite]

Best answer: Low dialogue volume is generally caused by a surround sound mix (which has a center channel) being played on a stereo speakers.
posted by wongcorgi at 1:30 PM on August 5, 2014 [1 favorite]

I think wrongcorgi is right. When you go from stereo to 5.1 Surround, all the dialog gets pushed to the center channel. If you don't have a surround setup, your missing a big chunk of the sound.
posted by doctor_negative at 2:13 PM on August 5, 2014

Best answer: i think wongcorgi really nailed it. You need to check the settings on your cablebox and make sure it's set to force stereo.

The sport broadcasting thing is something i've noticed that is just really annoying dynamic range compression, but the problem you had on CBS is absolutely playing just the side channels of a surround mix.

You should see if your TV or soundbar/receiver has something like SRS truvolume for stuff like the sports broadcasts. My tv and receiver both have it, and it's fucking great.

The surround mix thing is a problem i've encountered before though. And the cablebox was just set to "auto" instead of stereo.
posted by emptythought at 4:30 PM on August 5, 2014

Response by poster: I'm fairly certain I have the cable box set to force stereo, but I'll check again. I may also fiddle with the TV's audio setting, as well.

Thanks for the thoughts.
posted by kuanes at 5:09 AM on August 6, 2014

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