# Unit "s" unexpected behavior

**URL:** <https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347>\
**Category:** TidalCycles\
**Tags:** innards\
**Created:** [9 October 2022 10:11 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347 "2022-10-09T10:11:25Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![joanq](https://uzu.lurk.org/letter_avatar_proxy/v4/letter/j/bcef8e/32.png) [@joanq](https://uzu.lurk.org/u/joanq)\
**Post date:** [9 October 2022 10:11 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/1 "2022-10-09T10:11:25Z")

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While trying to document functions `speed` and `unit` I found that `unit "s"` behavior is not what I was expecting.

- What I expected: setting `unit "s"` changes the meaning of `speed` in that it refers to seconds. So, `d1 $ s "sax:5" # speed 2 # unit "s"` would make the sample last for 1/2 =half second. Its pitch would be changed accordingly.

- What it actually does: sample pitch changes exactly the same as with `unit "c"`, but it always lasts for one second, unless you set `begin` and/or `end`. For example:

```haskell
d1 $ s "sax:5" # speed 2.2 # unit "s" # end 0.5 # cps 0.4 # pan 0.8
d2 $ s "sax:5" # speed 2.2 # unit "r" # legato 1 # pan 0.2

```

If you listen to these two sounds at the same time, you can hear that the pitch is exactly the same for both, but the first one goes silent after half a second (independently of `cps` and `speed`).

What I want to know if this is the expected behavior, or it is a bug.

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**Author:** ![yaxu](https://uzu.lurk.org/user_avatar/uzu.lurk.org/yaxu/32/2_2.png) [@yaxu](https://uzu.lurk.org/u/yaxu)\
**Post date:** [11 October 2022 21:16 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/2 "2022-10-11T21:16:40Z")

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Hey @joanq, yes this looks like a bug! Either the behaviour wasn't ported from 'classic' dirt ([GitHub - tidalcycles/Dirt: Experimental sample playback](https://github.com/tidalcycles/dirt)) properly or something went wrong..

To memory though, I think how it should work is that `speed 2 # unit "s"` would actually slow down playback of the sample so that it would sound lower in pitch, and last two seconds.

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<div class="post-metadata">

**Author:** ![joanq](https://uzu.lurk.org/letter_avatar_proxy/v4/letter/j/bcef8e/32.png) [@joanq](https://uzu.lurk.org/u/joanq)\
**Post date:** [11 October 2022 22:12 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/3 "2022-10-11T22:12:22Z")

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It seems like there is some missing part in the current code.

This is from `audio.c` in Dirt:

```haskell
  if (sound->unit == 's') { // unit = "sec"
    sound->accelerate = sound->accelerate / sound->speed; // change rate by 1 per specified duration
    sound->speed = sound->sample->info->frames / sound->speed / g_samplerate;
  }
  else if (sound->unit == 'c') { // unit = "cps"
    sound->accelerate = sound->accelerate * sound->speed * sound->cps; // change rate by 1 per cycle
    sound->speed = sound->sample->info->frames * sound->speed * sound->cps / g_samplerate;
  }

```

This is from `DirtEvent.sc` in SuperDirt:

```haskell
        if (~unit == \c) {
			speed = speed * ~cps * if(useUnit) { unitDuration } { 1.0 }
		};

[...]
		if(useUnit) {
			if(~unit == \rate) { ~unit = \r }; // API adaption to tidal output
			switch(~unit,
				\r, {
					unitDuration = unitDuration * ~length / avgSpeed;
				},
				\c, {
					unitDuration = unitDuration * ~length / avgSpeed;
				},
				\s, {
					unitDuration = ~length;
				},
				{ Error("this unit ('%') is not defined".format(~unit)).throw };
			)
		};

```

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<div class="post-metadata">

**Author:** ![joanq](https://uzu.lurk.org/letter_avatar_proxy/v4/letter/j/bcef8e/32.png) [@joanq](https://uzu.lurk.org/u/joanq)\
**Post date:** [14 October 2022 18:27 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/4 "2022-10-14T18:27:56Z")

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Issue opened: [unit "s" unexpected behavior · Issue #275 · musikinformatik/SuperDirt · GitHub](https://github.com/musikinformatik/SuperDirt/issues/275)

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<div class="post-metadata">

**Author:** ![joanq](https://uzu.lurk.org/letter_avatar_proxy/v4/letter/j/bcef8e/32.png) [@joanq](https://uzu.lurk.org/u/joanq)\
**Post date:** [14 October 2022 18:47 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/5 "2022-10-14T18:47:20Z")

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Independently of the possible bug, it seems strange to me that while `speed 2 # unit "c"` makes the sample go faster than `speed 1 # unit "c"`, this is not the case with `speed 2 # unit "s"`, which will make the sample go slower than `speed 1 # unit"s"`.

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**Author:** ![julian](https://uzu.lurk.org/user_avatar/uzu.lurk.org/julian/32/1398_2.png) [@julian](https://uzu.lurk.org/u/julian)\
**Post date:** [16 October 2022 11:20 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/6 "2022-10-16T11:20:01Z")

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It is possible that my implementation is wrong, I may have misunderstood what it should do at the time. Strange that nobody noticed :).

The current implementation is as follows:

- `"r"`: changes `sustain`
- `"c"`: changes `sustain` and `speed`
- `"s"`: changes `sustain`

All this applies only to samples and is overridden by `legato`.

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<div class="post-metadata">

**Author:** ![joanq](https://uzu.lurk.org/letter_avatar_proxy/v4/letter/j/bcef8e/32.png) [@joanq](https://uzu.lurk.org/u/joanq)\
**Post date:** [16 October 2022 17:52 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/7 "2022-10-16T17:52:03Z")

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I'm leaving `unit "s"` undocumented until something is decided about how exactly it should behave.

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<div class="post-metadata">

**Author:** ![julian](https://uzu.lurk.org/user_avatar/uzu.lurk.org/julian/32/1398_2.png) [@julian](https://uzu.lurk.org/u/julian)\
**Post date:** [27 October 2022 11:39 UTC](https://uzu.lurk.org/t/unit-s-unexpected-behavior/4347/8 "2022-10-27T11:39:27Z")

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Yes, as soon as this is clear, it should be easy to implement.