Thread: MIDI transport inoperable -- Behringer UFX1204
Brought to you by:
aeb,
bencollins
From: John C. <joh...@gm...> - 2016-06-26 05:52:27
|
I am having an unresolved issue with the MIDI transport control section of the Behringer UFX series mixer. [UFX1204] This device is equipped with two interfaces. Firewire and USB. It is both an audio interface and a MIDI control surface. I am using the most recent kernel: --- Linux w530 4.6.2-hz1000-rt3 #3 SMP PREEMPT RT Thu Jun 23 11:41:06 CEST 2016 x86_64 GNU/Linux Accessing the device uses the following modules: --- snd_firewire_lib 32768 1 snd_bebob snd_rawmidi 32768 4 snd_firewire_lib,snd_bebob,snd_usbmidi_lib,snd_seq_midi snd_pcm 106496 9 snd_firewire_lib,snd_pcm_oss,snd_usb_audio,snd_bebob,snd_hda_codec,snd_hda_intel,snd_hda_core firewire_ohci 40960 0 firewire_core 65536 3 snd_firewire_lib,snd_bebob,firewire_ohci crc_itu_t 16384 1 firewire_core USB MIDI interface to-and-from the transport section of the device works flawlessly. >From the same application software Firewire MIDI communication to the device drops messages. I have read that MIDI section of the linux Firewire stack is not respecting the protocol rate limit. ref: http://mailman.alsa-project.org/pipermail/alsa-devel/2014-April/075912.html --- 2.Data rate for MIDI substream With current implementation, the maximum data rate for MIDI substream in out-stream is one eighth of sampling rate. For example, at 48.0kHz, it's 6,000 bytes. This is excess over standard MIDI data rate, 3,125 bits per second. So a few devices can have buffer over flow when receiving much MIDI messages. For example, M-Audio Firewire 1814 transmits packets with discontinuity in this case. I guess that Fireworks based devices and some BeBoB based devices ignore MIDI messages in more than 8 data blocks of packets and this is vendor's effort for this issue. Drivers need a throttle for this issue but this is for future work. --- Conversely, the Firewire release notes say: https://ieee1394.wiki.kernel.org/index.php/Release_Notes/3.x#Linux_3.19 --- snd-firewire-lib . Limit MIDI transmission rate as per specification to prevent loss of messages. --- So I'm left to wonder what the actual status of the Firewire MIDI substream protocol is, as the behavior I see, dropped packets sent to the UFX1204, is consistent with data overruns. I am assuming that the message content is correct as the MIDI transport functions correctly when accessed via the USB interface. Should I expect this to work, or is this a known open issue? Thanks jCandlish . This inquiry was originally posted here: https://linuxmusicians.com/viewtopic.php?f=6&p=72314#p72314 |