Why not a ".TSX" Format for MSX Tapes???

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By bore

Expert (115)

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19-06-2014, 19:49

It is mostly irrelevant for anything that doesn't have to do with data preservation/restoration.
But every now and then someone digs out an old tape or an old disk that might contain stuff of interest.
If there is a format that allows to store "bad" rips together with information of what sections have high uncertainty then it would be nice to know about it.
msx.org might be the wrong forum to ask about it but since the thread was about tsx and there were claims that the format could achieve this I figured that it would be interesting to know how.

By Grauw

Ascended (8442)

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19-06-2014, 20:17

@bore No this place is fine.

I think for the thing that you mentioned, it is best to just store it in WAV format and develop a tool which can analyse it and say which regions have signs of deterioration and which are clean.

By Manuel

Ascended (15744)

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19-06-2014, 21:04

Good thing about the Eurosoft game releases: they check the loaded data with a checksum. Any dump that works is good Smile

Anyway, so I see your point now.

By Randam

Paladin (916)

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19-06-2014, 22:00

@sd_snatcher: the black bass, mystery house 1 and 2, some stuff from infogrames, phalanx, zarth etc.

By hit9918

Prophet (2867)

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19-06-2014, 23:40

The casette topics are going round and round with various expectations.
When in doubt, store it into game.wav.zip and in game.txt note where are the cracks,
what poke ado is needed to get the game to run, does it run in subslot, etc etc,
so you remember that in ten years.

preservation rule #1: "when you put the casette to the basement, you better have a WAV".

By hit9918

Prophet (2867)

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20-06-2014, 00:06

What about the sampling rate?
Well what hz does the DAC / ADC of the no name PC have?
Let's imagine you name 19.2khz and software aliases it with the 22.5khz DAC.
Aliasing, the result is like 11.25khz? Suddenly things are frightening close to the required 9.6khz.

The only thing I can make of this is "when in doubt, say 44.1khz".
When the no name hardware is 22.5khz, you get duplicated samples. The quality remains 22.5khz.

16bit is not needed. e.g. a bad crack is so big that you dont need 16bit to preserve it for analysis.
if 16bit were needed to display a thing, then it would be so tiny that it is no problem for casette loading.

result is mono 8bit 44.1khz.

but, if the drive has a stereo tone head.
the signal might appear better on one side.
then you should sample in stereo, and afterwards in the sound tool sum it up to mono.

By Grauw

Ascended (8442)

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20-06-2014, 00:14

You can just record at 16bit 44.1KHz stereo, and then downsample to 8bit 11.25 kHz mono, right?

But I would expect this is what the PC does when you tell it to record 8bit 11.25 kHz mono, if it can’t do so natively… I do think it’s better to sample at 11.25 kHz though, that’s a pretty standard sampling frequency, a direct division of 44.1 kHz that all hardware should support I think.

By hit9918

Prophet (2867)

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20-06-2014, 00:24

Yes it works if the hardware has no surprise sampling hz.

Trying to downsample in audacity, I did get funny results.
Whole passages lost their volume, like with a sine as envelope.
Maybe the whole thing was fourier transformed forth and back.
Maybe this is the right thing for "pitch music up 5% without hz quality stalling to halve rate", no idea.
But for casette signals it is bad.
One should look at the curves, there are short swings and there are double size swings.
And when they are no more after using some pitch feature, things went bad.

By sd_snatcher

Prophet (3068)

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20-06-2014, 00:24

Quote:

What about the sampling rate?
Well what hz does the DAC / ADC of the no name PC have?

I mean no offense, but just a reality check: aren't the cassette tapes being a bit overrated here? AFAICR the iron-oxide cassettes frequency range topped at 12.5KHz.

By hit9918

Prophet (2867)

hit9918's picture

20-06-2014, 01:01

@sd_snatcher, again a Nyquist thing Smile
The example was, when one thinks 19.2khz is a reasonable rate, but the unknown soundboard has 22.5khz. Then with the aliasing, the result is down to 11.25Hz.
Maybe no problem on a good tape, but what if there are worries and one thought of playing with filters later?

I don't know. And my suggestion is "when you dont know, and the game is important to you, better use high hz".

Like, in the usual "music quality" thinking, stereo is good, 16bit is good, but that is all not required for casette loading.
Except the hz. When in doubt, keep those better on the higher side.

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