[BUG]: WinMM app cannot send SysEx message with the length of 2049 bytes or more

[m-komo]

Windows Version

27813.rs_prerelease.250307-1407

Service Installation Method

GitHub

SDK version, if appropriate

1.0.3-preview-11.250228-237

Location

Application using WinMM MIDI 1.0 (Classic API)

Type of bug

Cannot send messages to MIDI 1.0 device

Steps to reproduce

If a WinMM app try to send the SysEx message with the length of 2049 bytes or more, it fails.
This issue occurs regardless of the driver.

1. Short INPUPT and OUTPUT connector of the UM-ONE to loop back messages.
2. Attach the UM-ONE to PC.
3. Open the Pocket MIDI and choose the "UM-ONE" as an InputPort and an OutputPort.
4. Open the System Exclusive window and load the attached "TestMIDI_SysEx2049.txt". It contains the single 2049 bytes SysEx message.
5. Click the "Transmit" buttons to send messages.

The app fails to transmit message.

If you load the attached "TestMIDI_SysEx2048.txt" which contains the single 2048 bytes SysEx message and transmit it, it works fine.
I verified that the Pocket MIDI can send 2049 bytes SysEx message with current MIDI stack (no MidiSrv).
So it might not an app issue.

Expected behavior

App can send SysEx message with the length of 2049 bytes or more.

Additional notes

No response

[Psychlist1972]

This also looks like a buffer overrun with the MIDI device.

We're seeing a number of cases where we're sending messages much faster than these MIDI 1.0 devices can handle them, and because there's no throttling, the devices end up failing. I'll look into this.

[m-komo]

I checked the USB log and confirmed that there was no USB Out transaction when I sent 2049 bytes SysEx message.
Nothing sent out to the device.

[Psychlist1972]

Thanks. I'll look into that.

[tosugawara]

I tested sending the 2049 bytes SysEx message to MIDI 1.0 device on the reported environment using our custom WinMM MIDI filer app, which is used for debugging sending/receiving SysEx messages.
In result, the app succeeded in sending 2049 bytes, and there were USB OUT transactions. But when using Pocket MIDI, it failed to do and there was no USB OUT transaction.

[Psychlist1972]

Note: I was able to reproduce this issue using internal loopback devices, so the issue is in wdmaud2.drv or the service. It's not specific to any drivers.