Safari on iPad fails to play multiple tracks about midi.js HOT 7 OPEN

I believe this is due to CPU overload. When used on lower end PCs I get odd problems. When used on the Mac with Safari or Chrome, the CPU is hit and the more sounds playing at once the more the sound quality is impacted. Removed the gain node helps significantly. I believe that when using web audio api, anything that requires sound processing like the gain will eat CPU. Works fantastic on Chrome for my quad core i7, but not so good on Chrome on my Acer Iconia W500 with the C50 atom cpu.

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In some ways, using elements may be better for performance on low end machines.

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Hi @kusog, Good point, there should be an option to turn on/off any special WebAudioAPI features, like gain support (and future effects) to support Mobile browsers more effectively. I'll take a look into this and add to the list for next release. Also, browser support for MIDI.js listed on the project page would be a boon.

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In the meantime, it'd be easy for you to detect iOS, and then have a conditional in the plugin.js that prevents linearRampToValueAtTime, and the createGain function from being run in the WebAudioAPI portion of the script.

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I discovered that the version of MIDI-js I am running will set gain volume above 1, yet the docs say the value should be between 0 and 1 as a decimal. When I did some tests and just hard coded the volume to 50, I get the bad scratchy sound on Safari. A test I made just working with web audio API works great on safari >6.0 with many sounds playing even with gain and no problems.

From: Michael Deal [mailto:[email protected]]
Sent: Tuesday, February 18, 2014 12:47 AM
To: mudcube/MIDI.js
Cc: kusog
Subject: Re: [MIDI.js] Safari on iPad fails to play multiple tracks (#64)

Hi @kusog https://github.com/kusog , Good point, there should be an option to turn on/off any special WebAudioAPI features, like gain support (and future effects) to support Mobile browsers more effectively. I'll take a look into this and add to the list for next release. Also, browser support for MIDI.js listed on the project page would be a boon.

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@kusog I noticed in the docs it says between 0-1 also but for some reason it requires -1 in order to turn the volume completely off... so I mapped from -1.0 to 1.0 for the MIDIPlayer demo. I've added an upwards constraint for values more than 1.0 in the latest push to prevent accidentally going out of range.

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The iPad is still a problem. I was using an older version of your library from Feb and your library worked reasonably well on the iPad in both safari and chrome. I just upgraded to the latest version and there are significant performance issues on Safari.

Let me know if I can help in any way. Unfortunately I don't have a Mac, so I can't debug anything on an Ipad. (Silly platform)

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