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Why is OTA DTV audio easily broken with weak signal?

5253 Views 17 Replies 12 Participants Last post by  Schmerpy
I use OTA HD, and sometimes I watch a weak channel. When the picture is even slightly garbled, the audio is intermittent. Why?

Audio is 448Kbps Video is 19200Kbps. It is 2.3% of the total amount of data for HD. So why is even a slight garble in video results in bad audio? I understand if bad reception causes me to lose say 10-20% of data, but what's the likelyhood that ALL of 2.3% of audio information is lost in there ALL THE TIME?

For analog OTA, the picture can be ridiculously fuzzy, and the audio would remain crystal clear.

I'm using a LG 50PK550, with the antenna plugged directly into the TV.
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Yep, ATSC uses a single data stream across the alloted bandwidth. It is an all-or-nothing system, but it uses Forward Error Correction so if you are getting dropouts you need to look at better reception gear and/or aiming if possible.

The old analogue NTSC system uses the alloted 6MHz of channel bandwidth by chopping it up into specific parts for video and audio, and not only that but a station's own video and audio signals would interfere with each other if they used the same modulation so NTSC was deliberately specified to use AM (Amplitude Modulation) for the video while the audio portion uses FM (Frequency Modulation).

That's why it is possible to receive NTSC analogue audio and/or video separately. :)
Thanks for that, Rick_Dude, very informative! Your post also makes an interesting corollary to GeorgeMX's post #3 in this thread: :)
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