Canadian TV, Computing and Home Theatre Forums banner

Why is OTA DTV audio easily broken with weak signal?

5262 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.
1 - 3 of 18 Posts
The audio stream and video stream are combined (muxed) at the source and broadcast. The TV tuner splits them apart (demuxed). When a data packet is received but corrupted both the audio and video are effected. As you know with digital data you can easily corrupt the data by changing a few bits. So you lose not only the few bits but the entire package of information. Plus with MPEG video it requires a few packets to build an entire image. With analog there are no packets. Analog signals are a different beast. Basically your TV can lock onto the analog audio signal easier than the analog video signal because there is less information encoded in the signal to extract.
seriously robust error correction
That would require a return signal. Much the same way cable systems use the return data channel.
I think you'll find the cable data return channel is for actual user data, not error correction.
Besides the FEC data, the RDC diagnostic page on my cable STB lists the numbers of retransmissions. Just saying.
1 - 3 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.