Covox player source code

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By ericb59

Paragon (1098)

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19-01-2015, 20:10

hi,

is someone have and can give me the source code of a covox player ?

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By st1mpy

Paladin (900)

st1mpy's picture

19-01-2015, 20:19

is that through the parallel port? (I wanted to build one, but I'm missing the centronics connector, where can I buy one?)

By NYYRIKKI

Enlighted (6016)

NYYRIKKI's picture

19-01-2015, 21:25

Yes I can:

	LD A,(HL)
	INC HL
	OUT (#91),A

(repeat enough many times)

By flyguille

Prophet (3031)

flyguille's picture

19-01-2015, 22:23

NYYRIKKI wrote:

Yes I can:

	LD A,(HL)
	INC HL
	OUT (#91),A

(repeat enough many times)

Big smile I would use some kind of low cost compression Tongue Big smile

By ericb59

Paragon (1098)

ericb59's picture

20-01-2015, 07:02

@nyyrikki : and what about the way to have the good sound speed ?

By Grauw

Ascended (10699)

Grauw's picture

20-01-2015, 10:18

You’ll have to calibrate using the VDP’s VBLANK signal, by playing a silent sample of frequency / 50 or frequency / 60 bytes and using a search pattern.

Add a 16-bit wait loop to the above code, and then with interrupts disabled execute something like the following algorithm:

Part 1, exponential search:

  1. Wait until VBLANK interrupt bit gets set
  2. Play the sample
  3. Read the VBLANK interrupt bit
  4. If the bit is not set, double wait counter and repeat from 2
  5. Let SLOW be the current wait counter, FAST be the previous wait counter

Part 2, binary search:

  1. Pick the average value of SLOW and FAST as wait counter
  2. Wait until VBLANK interrupt bit gets set
  3. Play the sample
  4. Read the VBLANK interrupt bit
  5. If the bit is set, let SLOW be the current wait counter
  6. If the bit is not set, let FAST be the current wait counter
  7. Repeat from 1 until SLOW and FAST are less than two apart

Pick a good initial wait counter value for 3.58 MHz to speed up the process a little. Use a non-silent sample for a nice sound effect Smile.

By Fabf

Champion (266)

Fabf's picture

20-01-2015, 19:54

And do you think a streaming player is possible without mass storage direct access?

By ericb59

Paragon (1098)

ericb59's picture

20-01-2015, 20:00

Fabf wrote:

And do you think a streaming player is possible without mass storage direct access?

without ? or with ? mass storage direct access ?

By Fabf

Champion (266)

Fabf's picture

20-01-2015, 20:29

with mass storage direct access it should be possible as it's done with EVA.

By karloch

Prophet (2159)

karloch's picture

21-01-2015, 00:09

I was always so curious of how Covox sounds. Is there any mp3 record of it?

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