Clemens Ladisch <clemens@xxxxxxxxxx> writes: > David Kastrup wrote: >> If you want to hook up several ones of those via a USB hub, make sure >> that this hub has a separate "Transaction translator" per port so that >> a USB1.1 transaction from one Midi interface does not keep other >> transactions from happening: the 12Mbps limitation should only be per >> Midi interface, not per aggregating hub which can talk at 480Mbps to >> the computer. > > MIDI's speed of 0.03 Mbps is less than one percent of the USB 1.1 limit; > the lack of a transaction translator does not matter at all (unless > other, high-speed USB devices are connected to the hub). If we are aggregating 4 4-port interfaces used in two directions (USB rates are half-duplex), we need 32 times the bandwidth. So we are already at 1Mbps of raw data rate without any packaging. 90% of the full-speed bandwidth can be reserved for isochronous transfers which MIDI isn't. Queuing theory tells us that independent events close to filling up a given bandwidth tend to stack up, so in what order is a single transaction translator going to schedule transfers? What will be the effect on jitter? And events created by arrangers are not actually independent: time codes and chord notes and drums are coming out back-to-back. You'll be getting to "nobody will ever need more than 640kByte" territory sooner than you'll think... -- David Kastrup _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx https://lists.linuxaudio.org/listinfo/linux-audio-user
