Discussion in "New Ideas regarding projects" started by    Ajay    Sep 7, 2007.
Thu Apr 03 2008, 12:34 PM
#21

Thankx Sashi,

i'll try that, BTW i was thinking of using the spare timer to keep track of the length of


the message ,if i know the duration of the message played for eg. 5 secs, i can reload

the DPTR to the first value of the table after completion of 5 every secs . to get 5

sec delay i could use a tick of 50msec(interrupt @ of 50mSec) and a counter for 100

will give 5000msecs.


arun
Fri Apr 25 2008, 08:01 PM
#22
Hello forum,

as posted earlier i have success with BTC encoder using 8051 single port pin playback,

the audio file is sampled at 15625Hz, played back on a port pin @15625 bits per sec,

the BTC encoder outputs the audio into stream of 1 bits which need to be played back

using interrupt


now i want to playback using a 8 bit DAC, to playback the BTC encoder 's 1-bit stream

but i have few doubts :

1) instead of playing 1 bit at a time @ of 15625 Hz, can i play 8bits @ 15625/8 Hz i,e

1953 Hz ? will this give same output

2) will using DAC improve playback clarity ?

Arun
Sat Apr 26 2008, 07:15 AM
#23

Hello think tanks ,

any comments on my last post

Arun
Sat Apr 26 2008, 11:50 AM
#24
well you need to do 8-bit sampling, just like PCM wav sound its much more clear but the thing is it takes lot of memory.. you might need an eeprom to store data then..
can be a good project if you can implement playing a wav file stored in eeprom and then playback using 8051
also you can try recording also.. via adc, sample it at 8k and then store that 8-bit data
Sat Apr 26 2008, 11:00 PM
#25

Thanks Ajay


Arun
Sat Apr 26 2008, 11:11 PM
#26
Years ago i built a simple(no uC, only counter and eprom) wave player.
Wave files are resampled at 8KHz and converted to SND then are stored in eprom(27c256/512/1024)
Obviously this is usefull only for short sound.
Regards

P.S.
If someone want play with it i have the schematic somewhere
Mon May 12 2008, 06:39 PM
#27
Hello Guys,

since past 2 weeks i have been working on Roman black's BTC encoder since i didn't want to give up so easily, here are my findings :

1) the output file by the encoder is nearly 1/8th size of the original file - how does he do it? simple , 8:1 Compression , he selects the first MSB of the 8 bit sample and knocks off the remaining 7 bits of the sample byte.

2) clarity Issues - the clarity we get when a sound is played at 8Khz with 8bit sampling can be achevied on BTC but you have to choose to sample it at a very high rate of 48Khz (i,e 8 times faster) to get the same clarity, again you this won't reduce your output file size,

for eg: 1 sec sound at 8Khz, 8 bit has 48,000bits file size same with BTC encoder a 1sec sample at 48Khz rate has 48,000bits file size. so if you want clarity then your BTC doesn't Help you reduce the file size

3) don't get carried away when you select sample rates like 15,625Hz, 22,050Hz etc in BTC options - a 8Khz, 8 bit sample sounds a lot better than 15,625Hz,1 bit BTC sample Why ? in reality it BTC plays the sample at 15,625/8 Hz rate i,e 1,953Hz , 8 bit sample which is creepy when compared to original 8000Hz, 8bit sample

1) instead of playing 1 bit at a time @ of 15625 Hz, can i play 8bits @ 15625/8 Hz i,e

1953 Hz ? will this give same output




i got my answer, YES, it can be played but it gives same harsh sound quality.


hope these findings might help someone


Arun
Sun May 25 2008, 02:40 AM
#28
hey arun....i m not gettin a hang of da btc software...i mean it does convert da wave file into a binary output...but how do i store these values in 8051...how do i get da hex vaues for da look up table...i know dis is a dumb doubt...but i m a newbie.. :-) ...do reply...thanks in advance..
Sun May 25 2008, 05:54 AM
#29


Years ago i built a simple(no uC, only counter and eprom) wave player.
Wave files are resampled at 8KHz and converted to SND then are stored in eprom(27c256/512/1024)
Obviously this is usefull only for short sound.
Regards

P.S.
If someone want play with it i have the schematic somewhere

GioppY



hey Gioppy,
I would certain;y like to see how u stored it in the eprom without a uC .
Can u send me the schematic or tell me about the logic?
thanks in advance
Sun May 25 2008, 06:53 AM
#30

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