# [PD] For sample players based on [line~], [vline~], or [phasor~], how can we be sure all samples are being played?

Reed Perkins reedperkins32 at gmail.com
Mon Mar 23 05:50:50 CET 2015

```Hi Jonathan. Thank you for the reply. I still have a question about
something you wrote, with my original question reproduced below:

3. Does the output of [line~] and [vline~] vary due to being asked to
generate a ramp faster or slower? If I ask [line~] to go from 0-555987 in
3789 milliseconds, will the actual output be the same or different if I
then ask [line~] to go from 0-9876545 in 40 milliseconds

​You wrote
: "I'm not sure what you're asking.  Are you asking whether the samples
output from 0-555987 will be the same in both cases?  If so, the answer is
no.  The [line~] object is outputting floating point numbers in the range
you specify, over the duration you specify, aligned to block boundaries."

What I meant to ask is whether or not [phasor~], [line~], and [vline~]
behave the same in terms of outputting sequential values regardless of the
"speed" they are "driven at".

>From what I understand now, if you "drive" [line~] at the speed of the
sample rate, the output should be a steady stream of numbers that increase
by 1 from number to number.
​ However, if you try to "drive" [line~]​ at a speed that is faster or
slower than the sample rate, you'll get dropped samples or duplicated
samples, respectively.
So in this example:

|
[line~]
|
[tabread4~ array1] <--where array1 is a size of 41000

- If we were to print the output of the first ten
​numbers of [line~]​
, it should look like this: 0,
​ ​
1, 2, 3, 4, 5, 6, 7, 8, 9
​.​
​

- If we change the time in the message box to 2000, does the output of
line become 0, 0, 1, 1, 2, 2, 3, 3, 4, because we are now taking twice as
long to read through the table?
- If we change the time in the message box to 500, does the output of
the [line~] become 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, because now [line~]
has to skip samples in order to reach the end goal of 40999 in time?

I did some tests using the patch I outlined above using [print~] and these
stipulations seems to hold true. So now I am curious about what
[tabread4~]​ does. For the second scenario I outlined (2000ms time), does
[tabread4~] change 0, 0, 1, 1, 2, 2, 3, 3, 4, 4... into 0, 0.5, 1, 1.5, 2,
2.5, 3, 3.5, 4, 4.5...? Or in the third scenario (500ms time), does
[tabread4~] change, 0, 2, 4, 6, 8, 10... into 0, 1, 2, 3, 4, 5, 6...?

​

On Sun, Mar 22, 2015 at 10:43 AM, Jonathan Wilkes via Pd-list <
pd-list at lists.iem.at> wrote:
> On 03/20/2015 12:57 PM, Reed Perkins wrote:
>
> Hello all,
>
> [line~], [vline~], and [phasor~] are used to generate line ramps in basic
> sample-playback patches. The output of these objects is usually multiplied
> by the total number of samples in a sound file (that has already been
> into an array or table) and fed into the input of something like
> [tabread4~]. In other words, we use these line-ramp objects to traverse
the
> indices of a table where a sample is loaded at a given speed.
>
> My questions are these:
>
> 1. Do these line-ramps generate enough numbers such that every sample in a
>
>
> No.  (And I assume you are wanting the values of the table to be output
one
> after the other, in sequence, when you output them as a signal.)
>
> The determining factors for how table values are output: a) ramp duration
> (in time units), b) ramp height (end value - start value), c) the sample
> rate, and d) whether the object doing the reading is interpolating the
index
> values.
>
> The sample rate in Pd is fixed, so you are only guaranteed to read every
> table value when the ratio of ramp height/duration matches the sample rate
> ratio.  If you wanted something like [line~] and [tabread~] to guarantee
> that every sample of the table is read/output/whatever, you'd need a
system
> in which the sample rate changes based on the size of the array being
>
>
> 2. Does it matter if, say for example, [tabread4~] receives a decimal
number
> for an index, like 333987.8, which can be caused by multiplying the output
> of [phasor~] (which goes from 0-1) by the total amount of samples
(usually a
> much larger number).
>
>
no
> interpolation so the number after the decimal point in your index wouldn't
> make any difference.
>
> For example:
>
> [0 44099 2000(
> |
> [line~]
> |
> [tabread~ array1] <-- a table of size 44,100
>
> This will output every value of your table twice in a row, because your
> taking twice as long to read the entire table.  However, that's probably
not
> what you want, and if you listen to that results vs. [tabread4~], you'll
> hear why interpolation is a good thing in this case.
>
>
> 3. Does the output of [line~] and [vline~] vary due to being asked to
> generate a ramp faster or slower? If I ask [line~] to go from 0-555987 in
> 3789 milliseconds, will the actual output be the same or different if I
then
> ask [line~] to go from 0-9876545 in 40 milliseconds
>
>
> I'm not sure what you're asking.  Are you asking whether the samples
output
> from 0-555987 will be the same in both cases?  If so, the answer is no.
The
> [line~] object is outputting floating point numbers in the range you
> specify, over the duration you specify, aligned to block boundaries.
>
>
> I realize this is totally theoretical, because in all honestly I wouldn't
be
> able to hear a difference if samples are being skipped, but I want to know
> :)
>
>
> But you do.  If the sample rate is 44,100 samples per second, and you read
> from 0 to 44,099 in one second with [tabread~] you'll hear all the samples
> being output.  But if you read from 0 to 44,099 in _half_ of a second
you'll
> be skipping every other sample.  You'll certainly perceive the difference
as
> the sound recording going _twice_ as fast.
>
> Essentially, the [tabread4~] object is for those situations where you know
> you'll be playing back at a ramp height/duration ratio that doesn't match
> the sample rate ratio.  Or where you'll often be speeding up or slowing
> down.
>
> -Jonathan
>
>
>
>
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