Why not a ".TSX" Format for MSX Tapes? | MSX Resource Center (Página 9/13)

Por hit9918

Prophet (2932)

20-06-2014, 01:05

While with a tool generated .wav file, a thing "as solid as purely digital data", 9.6khz .wav did happily load.

Por hit9918

Prophet (2932)

20-06-2014, 01:13

Oh wait, and let us not forget, when the casette has 12.5kHz music, then that is like 25khz DAC!

The "computer hertz" is the sample values per second, and a tone Hz needs at least two samples.
Similar, with 50hz monitor, the sound / vibrato you can make at vertical blank interrupt rate is max 25hz.

Por hit9918

Prophet (2932)

20-06-2014, 01:20

Just found a snippet, http://en.wikipedia.org/wiki/44,100_Hz
"Firstly, because the hearing range of human ears is roughly 20 Hz to 20,000 Hz, and via the Nyquist–Shannon sampling theorem the sampling frequency must be greater than twice the maximum frequency one wishes to reproduce, the sampling rate therefore had to be greater than 40 kHz."

So here is hinted how the DAC hz must be twice the music hz.

Por hit9918

Prophet (2932)

20-06-2014, 01:24

Well and those theorems always sound like big math, but the basic thing is easy:

x x x
 x x x
 
up down up down... for a music hz you need an up plus a down.
needing two values in the thinking of computer RAM and DAC rate.
"music hz = halve of DAC hz"

Por sd_snatcher

Prophet (3659)

20-06-2014, 01:30

@Randam
Thanks!

BTW, i found a disk version of Mystery House at this site. I'll take a look at the other games.

Por hit9918

Prophet (2932)

20-06-2014, 01:36

But wait... and the 9.6khz casette rate I talked about again is of the DAC hz kind, not the music hz.
Heck it is braintwisting
2400 baud, 4 ppi values per bit.

Then 4.8khz "music quality" should be enough for a tape.
When tapes have 12khz, how on earth could there ever be load error. Because tapes are unreliable

Like, when a tape somewhere has one hole of ten milliseconds.
The dolby C freak with hifi supertower will never note
But your little datasette will note and the Alien 8 doesnt load

Por sd_snatcher

Prophet (3659)

21-06-2014, 00:59

Some more juicy information I found and I hope it helps to enrich this discussion: The page-17 of the MSX Technical Handbook states that the MSX cassette interface must have a low-pass filter for 3KHz, and a high pass filter for 16Hz~200Hz.

The modulation used is FSK.

Note: This low-pass filter requirement seems to have been removed on MSX2.

Por sd_snatcher

Prophet (3659)

06-03-2016, 05:05

@hit9918

IMHO, your tool is awesome for tape storage. If you could just add cas to wav conversion and 1200bps (thus 4.6KHz) support it would be perfect.

Por Pablibiris

Paragon (1815)

06-03-2016, 10:56

And what about a .tzx format? I think Manolito opens this thread for this reason

Por hit9918

Prophet (2932)

06-03-2016, 18:25

I dont know the CAS format, it is a bigger topic than my whole tool.
It would be nice if tools could be plugged together in a batch file.
It would be nice if a batch file was same language as the tool is written in.
One nice thing about MSX BASIC is that everyone got it ready installed, hum.
Well my tool was thought for crossdev. But otherwise such tools could be written for the MSX.
But then the emu should have "harddisk-as-dir".
Ok, now my thoughts slipped to "things like cas tools done on the MSX"