On Thu, 8 Oct 2015, Keith A. Milner wrote:
On Thursday 08 Oct 2015 01:51:20 Keith A. Milner wrote:
On Tuesday 06 Oct 2015 20:58:01 Keith A. Milner wrote:
OK, so it seems that this hardware is substantially the same as the GT-100 which has previously (and recently) been raised as a problem on ALSA.
I'm getting somewhere...
With the following quirk I am getting audio playback with aplay. I have what seems like correct MIDI interfaces working (although not fully tested).
However, recording does not seem to work.
I should add that, by "does not seem to work", the interface is seen, but nothing records. When using audacity, for instance, the playhead seems to get stuck and doesn't advance.
How does it look in Wireshark? Does the isochronous transfer for the capture direction start?
Actually, looking at your lsusb -v dump of the GT-001, I notice the following:
Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x0d EP 13 OUT bmAttributes 5 Transfer Type Isochronous Synch Type Asynchronous Usage Type Data wMaxPacketSize 0x0070 1x 112 bytes bInterval 1
Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x8e EP 14 IN bmAttributes 37 Transfer Type Isochronous Synch Type Asynchronous Usage Type Implicit feedback Data wMaxPacketSize 0x0070 1x 112 bytes bInterval 1
When the Isochronous Synch Type is Asynchronous, there must be a feedback channel where the USB device reports back information so that it can adjust the output sampling rate (http://wiki.osdev.org/Universal_Serial_Bus#Asynchronous_Endpoints).
I might be barking up the wrong tree here as I'm new to this, but it looks as if endpoint 0x8e is providing the feedback data, and there doesn't seem to be any other isochronous endpoint defined in the lsusb dump which could be used for the actual capture cdata.
I'm not sure what 'Implicit feedback Data' means exactly though - is the feedback data multiplexed with the capture data perhaps?
/Ricard