timing

[errorsmith]

hello,
first i want to thank you for developing this tool! I always wanted to have something like this. I hope i can contribute to improve it.

I have a Wacom sapphire cte-430. The midi loopback device is midi yoke.

Here are my test/bugs/improvement request.
The mentioned wav-files can be downloaded here: www.errorsmith.de/unlinked/tablet2miditest.zip

I made following tests concerning the timing of table2midi:

1. To test the delay between the actual physical hit of the pen on the tablet and the received midi event, i miked this hit with a microphone, routed it in reaktor via my soundcard and recorded it together with the received midi gate in reaktor as an audiofile. The same i did with my midikeyboard. The audiobuffer of my soundcard (RME Hammerfall) was set to 11 ms. What i meassured disapointed me much: While there is no delay between the micrphone click and the midi gate of my midi-keyboard. (Since the microphone click is of course delayed by the bufferlength of my audiocard, there must be compensation for that somewhere!) ,the delay when i use the midi2table is big and varies (timing jitter). It is in the range 20ms to 40 ms, which makes it pretty useless for triggering notes and even for modulation this delay is at least unsatisfing! (see "keyboard gate versus mic.wav" and "tablet2midi gate versus mic.wav"

2. I recorded the received controller from table2midi as audio signal (i used reakor for it again) and compared it to the recording of the modulationwheel of my midi-keyboard. I tried to make a sweep on both controller of the same duration at around 200-400 ms. I noticed that the table2midi signal is more jagged as the modwheel signal. I guess that the sample rate at which the tablet is sampled at is smaller as the one of my midikeyboard. I wish i can adjust this rate or it should be set to a value below 10ms period. Also the tablet2midi signal has a strange distribution of events. Please have a look at tablet sweep.wav in an editor: At sample 5928 there is an event that looks as if it is much more delayed than the following one for instance. I would expect it to be much more in the middle between the previous one and the following one. Please remember that i made straight sweep by hand. The corresponding recording of the modwheel shows a much more even distribution of the events.



3. See xy.wav: Here i recorded the controller of the xy field. I created jumps by clicking on a upper left position of the tablet, lifting the pen and then clicking on a lower right postion. As you can see in the wav file, the x and y controller aren't updated at the same time, which should be. One would want to sample and hold the controllers on note-on in his aplication. For example x could be pitch, y could be velocity of a note on. That would also require that the midi-gate from tablet2midi should be sent last, means after x and y. I see that this is only a feature that might be interesting to reaktor or max users, where you can tranform midi signals. But it leads maybe to another request: tablet2midi should include a "Keyboard" Object that sends out midi notes with variable pitch, like Ribbon Controller ala R2M from Doepfer! Uuuhhh there is a ton of features just in that Object that comes up in my mind. For more ideas check the R2M Manual which is available on the website: www.doepfer.de

that's it for now.
I hope it's a help.

all the best,
erik

[ohm]

answered in a the "bugs" thread