Comment 16 for bug 785939

This USB Monitor software is part of Device Monitoring Studio, which is also able to capture HID traffic. I just noticed that the mixer shows up differently before/after I start Scratch Live.

Before starting Scratch Live:

Universal Serial Bus controllers
    USB Composite Device
        Port_#0002.Hub_#0004
        (Standard USB Host Controller)

Sound, video and game controllers
    USB Audio Device
        0000.001d.0000.001.002.000.000.000.000
        (Generic USB Audio)
    USB Audio Device
        0000.001d.0000.001.002.000.000.000.000
        (Generic USB Audio)

Human Interface Devices
    USB Input Device
        0000.001d.0000.001.002.000.000.000.000
        (Standard system devices)

After starting Scratch Live:

Universal Serial Bus controllers
    Rane TTM 57SL
    Port_#002.Hub_#0004
    Serato

The mixer goes from being a composite USB device, comprising 2 audio devices and an HID device, to a single Rane TTM 57SL device. The configuration before starting Scratch Live looks similar to the output of "sudo lsusb -v" under Linux. I think Scratch Live installs a new driver for the mixer when it starts up. This seems to be mentioned in the manual (http://serato.com/downloads/files/67733/Scratch_Live_TTM_57SL_Manual.pdf): "Additional Windows Drivers: Once Scratch Live is installed, any additional hardware that is connected will be recognized and the drivers will be automatically installed."

I've tried setting up the software to sniff packets for the HID device, but as soon as Scratch Live starts up, the capture stops because the devices change. If I monitor the new Rane TTM 57SL device, then there are various "views" available: Raw Data View, URB View, Packet View, HID View. I see a constant stream for each view except HID, which is blank, even when I play around with the checkboxes in Scratch Live, so it doesn't look like any HID packets are being sent.

I think if there are any important control signals, they should be in that log of the initial handshake that I posted earlier? However, I expect a lot of it might just be querying the mixer to figure out which driver to install. I should mention that the Rane TTM 57SL device driver that gets installed once Scratch Live starts, only persists for as long as the USB cable is connected. If I unplug it, and then plug it back in, the mixer goes back to being detected as a composite USB device.

Sean: If Scratch Live is running in internal mode, then it does notice immediately when the USB cable is disconnected, and stops working until you plug it back in. I think this is partly due to the fact that Scratch Live only outputs audio via the mixer (since there's no option to output audio locally, like in Mixxx). What does this tell us?