Old 06-09-2018, 04:16 PM   #1
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Default midi does not quantize to grid

Strange issue

I record - choose grid - quantize - nut no matter what grid i choose there is a little gap between start of midi file and the grid

Søren Bendixen
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Old 06-10-2018, 11:34 PM   #2
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- Which Action exactly do you use for quantizing ? (it's name please).
- I assume you are in MIDI Editor when you are doing the quantize action ?
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Old 06-11-2018, 12:02 AM   #3
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Originally Posted by audiotect View Post
Strange issue

I record - choose grid - quantize - nut no matter what grid i choose there is a little gap between start of midi file and the grid

Søren Bendixen
Are you referring to the start of the MIDI item, or the start of MIDI notes?

I think that you have run into the quantize-to-tick phenomenon, which some users find quite surprising:

If you change the MIDI editor's timebase from "Project beats" to "Source beats", you will notice that the notes can suddenly be nicely aligned with the source beats' grid.

The problem is probably that the MIDI item's start position is slightly off-grid, so the MIDI item's internal grid is slightly misaligned with the project's grid.

REAPER uses the standard specifications for MIDI files (with only a few exceptions) to represent the data in each individual MIDI item. According to these specifications, MIDI events can only fall on discrete tick positions, counted from the *start* of the item's source. By default, REAPER uses a PPQ of 960 ticks per quarter note.

So if your item does not start on a grid position, the ticks *inside* the item may not correspond to the project's grid. It is safest to always ensure that all MIDI items start on a grid position.

More info in Comprehensive ELP MIDI rounding problem thread (FIXED) and Error MIDI editor in Reaper (FIXED).

Also, beware of stretched MIDI items, as the stretching may de-sync the MIDI item's internal ticks/grid vs the project grid: Cut/Paste in ME, can someone explain this?

The best way to avoid these issues is to make sure that every MIDI item's *source* starts on the grid (even a very fine grid like 1/128).

NB: To complicate matters, there may a difference between
1) the start position of the MIDI source, and
2) the start position of the MIDI item in the arrange view, which is the visible part of the MIDI source.

When you drag a MIDI item's border, you change the visible part, but not necessarily the source position.

There are several ways to correct an existing MIDI item and its source simultaneously, for example:
* Glue the item
* Split the item at the nearest grid, after unlooping/unpooling the item and enabling Preferences -> "Allow trim of MIDI items when splitting").
* Drag the edge if the item and then go to Item Properties and set "Start in source" to 0.
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