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'PCM Audio'
1999\11\02@174019 by Martin McCormick

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       I just realized that the 17C43 does not have an on-board
analog to digital converter.  I do have a TI 8-bit
successive-approximation type converter that I can use and I also have
a PIC1671 which I could use.  Since I must use an external
device, I am wondering about the ISDN telephone chips as are used in
Sun work stations.

       They have the A/D and D/A built in as well as some low-pass
filters.  The only thing I see right off the bat is that they speak in
a 64-KB data stream which might or might not get along with the serial
USART in the 17C43.  If I use the TI chip or the 16C71, I can use the
PWM output in the 17C43 as the D/A end of the system.  How bad does
8-bit PCM sound?  The audio needs to be at least telephone quality,
but not much better.

Martin McCormick

1999\11\02@184441 by Dennis Plunkett

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At 16:39 2/11/99 -0600, you wrote:
>        I just realized that the 17C43 does not have an on-board
>analog to digital converter.  I do have a TI 8-bit
>successive-approximation type converter that I can use and I also have
>a PIC1671 which I could use.  Since I must use an external
>device, I am wondering about the ISDN telephone chips as are used in
>Sun work stations.
>
>        They have the A/D and D/A built in as well as some low-pass
>filters.  The only thing I see right off the bat is that they speak in
>a 64-KB data stream which might or might not get along with the serial
>USART in the 17C43.  If I use the TI chip or the 16C71, I can use the
>PWM output in the 17C43 as the D/A end of the system.  How bad does
>8-bit PCM sound?  The audio needs to be at least telephone quality,
>but not much better.
>
>Martin McCormick
>
>

Most 64Kbit stuff is framed on a packet of 125uS (That's micro section),
and nominaly has frame syc bits etc that are often dragged out of the
incomming stream, be this G.711, 7.03. After this it may turn into an
omnibus type format.
As for how bad does it sound, quite good if you are after voice only. If
you want music then you will have to compress the upper frequencies


Dennis

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