MAME Floppy sound emulation - Revision history

Mizapf at 11:32, 31 August 2016

2016-08-31T11:32:03Z

← Older revision		Revision as of 11:32, 31 August 2016
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	\| Match rotation period (usually 200ms) or multiple		\| Match rotation period (usually 200ms) or multiple
	\|-		\|-
	\| ~~XX_spin_start_empty~~.wav		\| XX_spin_loaded.wav
	\| ~~Starting~~ spindle motor~~, no~~ disk ~~inserted~~		\| Running spindle motor with floppy disk
	\| Match rotation period (usually 200ms) or multiple		\| Match rotation period (usually 200ms) or multiple
	\|-		\|-

Mizapf at 15:59, 26 August 2016

2016-08-26T15:59:23Z

← Older revision		Revision as of 15:59, 26 August 2016
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	MAME (or its subproject MESS) shows impressive precision for the emulation of arcade and computer systems. One thing that has been slightly out of scope was the emulation of physical phenomena outside of the computer system, in particular the sounds and noises that occur when you operate these systems.		MAME (or its subproject MESS) shows impressive precision for the emulation of arcade and computer systems. One thing that has been slightly out of scope was the emulation of physical phenomena outside of the computer system, in particular the sounds and noises that occur when you operate these systems.

			The following text elaborates on the state of the art of MAME 0.177.

	== Motivation ==		== Motivation ==

Mizapf: /* Improved concept */

2016-08-26T15:58:02Z

Improved concept

← Older revision		Revision as of 15:58, 26 August 2016
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	This proved to yield a really nice sound output that sounds much closer to the real device. However, the playbacks with a shifted pitch decrease the quality of the sound emulation again: An 8 ms seek sample is just not a 16 ms sample, played at double speed; recall the harmonics mentioned above.		This proved to yield a really nice sound output that sounds much closer to the real device. However, the playbacks with a shifted pitch decrease the quality of the sound emulation again: An 8 ms seek sample is just not a 16 ms sample, played at double speed; recall the harmonics mentioned above.

	Therefore ~~I'd recommend~~ to record many different seek samples for a drive and only use slightly changed pitch. A good collection would be 2ms, 6ms~~, 8ms~~, 12ms~~, 16ms~~, and 20ms. Slower step rates behave almost like separate steps, so they can be produced in the easy way by replaying the step sample.		Therefore we need to record many different seek samples for a drive and only use slightly changed pitch. A good collection would be 2ms, 6ms, 12ms, and 20ms. Slower step rates behave almost like separate steps, so they can be produced in the easy way by replaying the step sample.

	== Sample files ==		== Sample files ==

Mizapf: /* Challenges */

2016-08-26T15:55:09Z

Challenges

← Older revision		Revision as of 15:55, 26 August 2016
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	[[File:seek20_curve.png \| 800px]]		[[File:seek20_curve.png \| 800px]]

	~~If you measure~~ the distance between two ~~peaks, you will of course notice that~~ they are ~~20ms~~ apart. ~~And we have~~ to ~~admit that~~ it ~~has virtually no similarities~~ to ~~any part of~~ the ~~step sample~~.		Check the distance between two peeks; they are 20 ms apart, so each one is caused by a step during the seek process. Obviously, the seek sample looks very different to the step sample, and it is questionable whether it is possibly to turn either one into the other.

	Physically speaking, there are two points that explain this issue:		Physically speaking, there are two points that explain this issue:

Mizapf at 15:51, 26 August 2016

2016-08-26T15:51:46Z

← Older revision		Revision as of 15:51, 26 August 2016
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	Therefore I'd recommend to record many different seek samples for a drive and only use slightly changed pitch. A good collection would be 2ms, 6ms, 8ms, 12ms, 16ms, and 20ms. Slower step rates behave almost like separate steps, so they can be produced in the easy way by replaying the step sample.		Therefore I'd recommend to record many different seek samples for a drive and only use slightly changed pitch. A good collection would be 2ms, 6ms, 8ms, 12ms, 16ms, and 20ms. Slower step rates behave almost like separate steps, so they can be produced in the easy way by replaying the step sample.

			== Sample files ==

			These are the current sample files as of release 0.177. The XX prefix must be "35" or "525", according to the floppy type. You need at least one full set of 10 sample files. If a file is missing, floppy sound output is disabled.

			{\| class="plain" width="75%"
			! width="30%" \| File name
			! width="33%" \| Meaning
			! width="37%" \| Timing requirements
			\|-
			\| XX_spin_start_empty.wav
			\| Starting spindle motor, no disk inserted
			\| At least 50 ms
			\|-
			\| XX_spin_start_loaded.wav
			\| Starting spindle motor with floppy disk
			\| At least 50 ms
			\|-
			\| XX_spin_empty.wav
			\| Running spindle motor, no disk inserted
			\| Match rotation period (usually 200ms) or multiple
			\|-
			\| XX_spin_start_empty.wav
			\| Starting spindle motor, no disk inserted
			\| Match rotation period (usually 200ms) or multiple
			\|-
			\| XX_spin_end.wav
			\| Stopping spindle motor (with or without disk)
			\| less than 100ms (or we would notice the disk sound)
			\|-
			\| XX_step_1_1.wav
			\| Step sound in zone one, sample 1
			\| Comprise the whole step sound, at least 75 ms; should be clipped to start immediately
			\|-
			\| XX_seek_2ms.wav
			\| Seek sound at 2ms step rate
			\| Should be low volume, can be barely heard; at least 10 ms
			\|-
			\| XX_seek_6ms.wav
			\| Seek sound at 6ms step rate
			\| Most notable floppy drive sound; may be well hearable. At least 50 ms.
			\|-
			\| XX_seek_12ms.wav
			\| Seek sound at 12ms step rate
			\| May be well hearable. At least 75 ms.
			\|-
			\| XX_seek_20ms.wav
			\| Seek sound at 20ms step rate
			\| Very coarse sound, well hearable. At least 100 ms.
			\|}

			The step sound naming already suggests that there is a possible further enhancement: to use different samples according to the position on the disk, and then possibly different sounding samples in the same zone that would be picked at random. The step sounds are softer when the head approaches the spindle in the center.

			== Adapting to other drives ==

			Many drive brands have their specific sound, one could say, like a fingerprint. Therefore, while MAME delivers 20 sample files (10 for 5.25", 10 for 3.5" drives), you may want to use samples for your special disk drive. You'll have to proceed as follows:

			* Create your own samples directory (like ''mysamples'') and use that name in the mame.ini configuration file as value for the ''samples'' property
			* Record your own samples with the same names as above (according to the drive size)
			* Put those files into your mysamples directory.

			Concerning the seek samples, it may occur that you cannot make your disk drive use the mentioned step rates. This is not a problem as long as the emulation uses the same rates. You must provide those files, however. If the file is never used, you can put anything into it. Otherwise, if you want to provide something meaningful (just in case you do have that step rate in emulation), you can try to "forge" a sample.

			For instance, you may only have a 20 ms sample, but you cannot be sure that there won't be a 16 ms step rate at some time. If you cannot record a sample at that rate, load your 20 ms sample into an audio processing tool (like Audacity), and change its rate to 16 ms. In Audacity, you would have to apply the effect filter "Change speed". However, keep in mind that those samples are no real samples, and they likely sound weird: For human speech you could easily tell whether a recording is replayed at higher speed, or whether the speaker has a higher pitched voice; this is nearly the same effect here. For the same reason we cannot get along with a single seek sample and just modify its replay speed.

Mizapf: /* Improved concept */

2016-08-23T19:57:11Z

Improved concept

← Older revision		Revision as of 19:57, 23 August 2016
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	[[File:merged_seek.png\|600px]]		[[File:merged_seek.png\|600px]]

	At first we start with a step sample; then we switch to the seek sample. You do not notice this quick switch; it sounds as if it begins with the seek sample. We keep the position within the step sample, though: When the seek is over, the last step should resemble a single step, and then we resume the step sample.		At first we start with a step sample; then we switch to the seek sample. You do not notice this quick switch; it sounds as if it begins with the seek sample. We keep the position within the step sample, though: When the seek is over, the last step should resemble a single step, and then we resume the step sample. If you look closely you see that we resume the seek sample at a slightly later point of time (1/100 s); this way we can dampen the end pulse a little bit to make it more realistic - we are skipping the strongest peak.

	~~In fact~~, from a "tup-tup-tup" and a "rooooop", we create a "tu-roooooo-p" here. That is, we get to this solution:		Hence, from a "tup-tup-tup" and a "rooooop", we create a "tu-roooooo-p" here. That is, we get to this solution:

	* We start with a step sample.		* We start with a step sample.

Mizapf: /* Initial approach */

2016-08-22T22:28:59Z

Initial approach

← Older revision		Revision as of 22:28, 22 August 2016
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	Taking this list into account, we can easily define our requirements:		Taking this list into account, we can easily define our requirements:

	* We need samples of the turning disk without head movement. Since the head does not move all times, this is ~~quite~~ easy to ~~accomplish~~; we just need to record a sample of some longer disk operation.		* We need samples of the turning disk without head movement. Since the head does not move all times, this is easy to achieve; we just need to record a sample of some longer disk operation to get everything we need.

	* We also need samples of the head movement, the popping sounds as just mentionend.		* We also need samples of the head movement, the popping sounds as just mentionend.

	We can treat both as two sound sources and simply add the sample values on each sample step. This creates a mix of motor and stepper sound.		We can treat both kinds as two sound sources and simply add the sample values on each sample step. This creates a mix of motor and stepper sound.

	This was the first approach, and it worked already quite well, but not fully convincing.		This was the first approach, added to MAME with release 0.165, and it worked already quite well ... but not fully convincing.

	== The Real Thing ==		== The Real Thing ==

Mizapf: /* Initial approach */

2016-08-22T22:26:33Z

Initial approach

← Older revision		Revision as of 22:26, 22 August 2016
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	* The spindle motor produces a low humming sound while running. There may also be a specific start and stop sound, caused by the quick acceleration and slowing down of the rotation.		* The spindle motor produces a low humming sound while running. There may also be a specific start and stop sound, caused by the quick acceleration and slowing down of the rotation.

	* The floppy disk often causes a hissing sound, in particular the bigger 5.25" disks. The reason is that disk inside the protective enclosure stays in contact with the material. Moreover, when the enclosure is slightly bent or dented, the disk produces louder noises. The smaller 3.5" disks have hard enclosings that ~~leaves~~ enough space for the disk to turn without hearable sliding.		* The floppy disk often causes a hissing sound, in particular the bigger 5.25" disks. The reason is that disk inside the protective enclosure stays in contact with the material. Moreover, when the enclosure is slightly bent or dented, the disk produces louder noises. The smaller 3.5" disks have hard enclosings that leave enough space for the disk to turn without hearable sliding.

	* The head motor and the read/write head are the components with the most obvious sound production. The head motor is a stepper motor which moves the read/write head. Stepper motors have a noticeable sound; the moving head sounds as if it locks into some hole or hits an obstacle, but this is not the case. The rapid stop of the head movement is what causes the "pop" sounds.		* The head motor and the read/write head are the components with the most obvious sound production. The head motor is a stepper motor which moves the read/write head. Stepper motors have a noticeable sound; the moving head sounds as if it locks into some hole or hits an obstacle, but this is not the case. The rapid stop of the head movement is what causes the "pop" sounds.

Mizapf: /* Initial approach */

2016-08-22T22:26:08Z

Initial approach

← Older revision		Revision as of 22:26, 22 August 2016
Line 27:		Line 27:
	* The spindle motor produces a low humming sound while running. There may also be a specific start and stop sound, caused by the quick acceleration and slowing down of the rotation.		* The spindle motor produces a low humming sound while running. There may also be a specific start and stop sound, caused by the quick acceleration and slowing down of the rotation.

	* The floppy disk often causes a hissing sound, in particular the bigger 5.25 ~~inch~~ disks. The reason is that disk inside the protective enclosure stays in contact with the material. ~~When~~ the enclosure is slightly bent or dented, the disk ~~produced~~ louder noises. The smaller 3.5 ~~inch~~ disks have hard enclosings that leaves enough space for the disk to turn without hearable sliding.		* The floppy disk often causes a hissing sound, in particular the bigger 5.25" disks. The reason is that disk inside the protective enclosure stays in contact with the material. Moreover, when the enclosure is slightly bent or dented, the disk produces louder noises. The smaller 3.5" disks have hard enclosings that leaves enough space for the disk to turn without hearable sliding.

	* The head motor and the read/write head are the components with the most obvious sound production. The head motor is a stepper motor which moves the read/write head. Stepper motors have a noticeable sound; the moving head sounds as if it locks into some hole or hits an obstacle, but this is not the case. The rapid stop of the head movement is what causes the "pop" sounds.		* The head motor and the read/write head are the components with the most obvious sound production. The head motor is a stepper motor which moves the read/write head. Stepper motors have a noticeable sound; the moving head sounds as if it locks into some hole or hits an obstacle, but this is not the case. The rapid stop of the head movement is what causes the "pop" sounds.

Mizapf: /* Initial approach */

2016-08-22T22:25:14Z

Initial approach

← Older revision		Revision as of 22:25, 22 August 2016
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	Trying to go for such a physical emulation opens up a giant world of dynamic systems with complicated maths and considerable requirements for the emulating systems. Also, while there is an abundance of visual rendering system, there are not that many for audio rendering, at least to my knowledge.		Trying to go for such a physical emulation opens up a giant world of dynamic systems with complicated maths and considerable requirements for the emulating systems. Also, while there is an abundance of visual rendering system, there are not that many for audio rendering, at least to my knowledge.

	If we do not want to compute sounds, we have to use pre-defined sound clips or ''samples''. This is a proper way to emulate sounds for quite a long time, appearing in many applications. For our floppy ~~soound~~ emulation we need to find out what sounds have to be produced:		If we do not want to compute sounds, we have to use pre-defined sound clips or ''samples''. This is a proper way to emulate sounds for quite a long time, appearing in many applications. For our floppy sound emulation we need to find out what sounds have to be produced:

	* The spindle motor produces a low humming sound while running. There may also be a specific start and stop sound, caused by the quick acceleration and slowing down of the rotation.		* The spindle motor produces a low humming sound while running. There may also be a specific start and stop sound, caused by the quick acceleration and slowing down of the rotation.