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Variable audio delay to sync radio broadcast with HDTV for sports?

fustini

Howdy -

 

Back in the good ol' days of analog broadcast TV, I remember I could watch my beloved Chicago Bears and listen to the local radio broadcast of the game in sync.  With the advent of HDTV and digital cable, the radio broadcast is ahead of the TV, thus spoiling the suprise of a big play.

 

After a bit of searching, I came of cross this nifty product, SportSync Radio:

 

https://www.scannermaster.com/ProductDetails.asp?ProductCode=01-561060

 

It is a portable radio with a slider that delay the audio upto 8 seconds so that one can sync it up with the action on the TV.  Digging electronics & embedded systems, I figured it would be fun and a good learning experience to try to build my own DIY version.

 

I know a couple quick methods would be to use analog tape on a loop or use an old desktop or laptop with software to delay mic input.  However, ideally, I'd like to come up with an embedded system that uses digital electronics with minimal amount of software (maybe a microcontroller that ties together ADC, memory & DAC).

 

I came across this article in EDN:

 

Low-Cost Audio Delay Uses 1-bit ADC

http://electronicdesign.com/article/analog-and-mixed-signal/low-cost-audio-delay-line-uses-1-bit-adc8056.aspx

 

I really like this idea as it uses what seems to me to be minimal amount of components: op amp, d flip flop & shift register.  However, I'm bit unclear as to what type of shift register would be used.  The article states: the delay line can be any digital storage media.  It seems some type of memory with 1Mbit or more would be needed which is much different that the small 74x series shift register I'm familar with.

 

 

I thought it would be a good idea to see if anyone on element14 had do something similar or might have insight in building such a system.

 

 

Thanks!

Drew

http://twitter.com/pdp7

  • The article you quote is not a serious proposition for a working device. Sigma delta ADCs and DACs exist but you can't get something for nothing. CD quality audio is 44k x 16 bit samples per second per channel = 88k bytes/sec per channel. To store the same quality data as a bit stream you will need 704kbit/s.

    If you are happy with much lower quality (telephone) you can get down to perhaps 8000 x 8 bit samples per second which you could do on a small micro like an AVR with an external RAM chip (you still need 64 kbytes of RAM).

    Some of the ST ARM Cortex M3 chips have ADC, DAC and enough RAM on chip to do it all in one part - they have some very cheap dev tools as well so this might be a reasonable route.