Hi Jakob + all Just to let you know I have managed use alsa-midi-latency-test to test the latency of PianoBooster which is very bad at the moment but here are the results anyway: I know the timer tick is much to slow at the moment so I fix that problem and retest. I have used the midi through and a midi loop back cable to put alsa-midi-latency-test and PianoBooster into the midi test loop. My results for comparison without PianoBooster in the loop are pasted in at the end of this email Louis ==== RESULTS WITH PIANOBOOSTER ===== ./alsa-midi-latency-test -i 14:0 -o 24:1 -R -w 1 -r sched_setscheduler: Operation not permitted sample; latency_ms; latency_ms_worst 0; 14.39; 14.39 90; 19.98; 19.98 91; 23.72; 23.72 9999; 10.22; 23.72 ... 4.2 - 4.3 ms: 1 # 4.3 - 4.4 ms: 1 # 4.4 - 4.5 ms: 2 # 4.5 - 4.6 ms: 1 # ... 5.2 - 5.3 ms: 2 # 5.3 - 5.4 ms: 3 # 5.4 - 5.5 ms: 1 # 5.5 - 5.6 ms: 2 # 5.6 - 5.7 ms: 2 # 5.7 - 5.8 ms: 2 # ... 5.9 - 6.0 ms: 3 # 6.0 - 6.1 ms: 1 # 6.1 - 6.2 ms: 2 # 6.2 - 6.3 ms: 7 # 6.3 - 6.4 ms: 3 # 6.4 - 6.5 ms: 9 # 6.5 - 6.6 ms: 1 # 6.6 - 6.7 ms: 11 # 6.7 - 6.8 ms: 7 # 6.8 - 6.9 ms: 8 # 6.9 - 7.0 ms: 11 # 7.0 - 7.1 ms: 7 # 7.1 - 7.2 ms: 9 # 7.2 - 7.3 ms: 11 # 7.3 - 7.4 ms: 15 # 7.4 - 7.5 ms: 8 # 7.5 - 7.6 ms: 12 # 7.6 - 7.7 ms: 9 # 7.7 - 7.8 ms: 9 # 7.8 - 7.9 ms: 20 # 7.9 - 8.0 ms: 19 # 8.0 - 8.1 ms: 27 ## 8.1 - 8.2 ms: 20 # 8.2 - 8.3 ms: 23 # 8.3 - 8.4 ms: 25 ## 8.4 - 8.5 ms: 28 ## 8.5 - 8.6 ms: 31 ## 8.6 - 8.7 ms: 47 ### 8.7 - 8.8 ms: 37 ## 8.8 - 8.9 ms: 40 ### 8.9 - 9.0 ms: 39 ## 9.0 - 9.1 ms: 49 ### 9.1 - 9.2 ms: 55 #### 9.2 - 9.3 ms: 81 ##### 9.3 - 9.4 ms: 68 #### 9.4 - 9.5 ms: 114 ####### 9.5 - 9.6 ms: 100 ###### 9.6 - 9.7 ms: 128 ######## 9.7 - 9.8 ms: 147 ######### 9.8 - 9.9 ms: 238 ############### 9.9 - 10.0 ms: 351 ###################### 10.0 - 10.1 ms: 492 ############################### 10.1 - 10.2 ms: 578 ##################################### 10.2 - 10.3 ms: 681 ############################################ 10.3 - 10.4 ms: 781 ################################################## 10.4 - 10.5 ms: 696 ############################################# 10.5 - 10.6 ms: 710 ############################################# 10.6 - 10.7 ms: 737 ############################################### 10.7 - 10.8 ms: 692 ############################################ 10.8 - 10.9 ms: 567 #################################### 10.9 - 11.0 ms: 525 ################################## 11.0 - 11.1 ms: 322 ##################### 11.1 - 11.2 ms: 201 ############# 11.2 - 11.3 ms: 152 ########## 11.3 - 11.4 ms: 105 ####### 11.4 - 11.5 ms: 82 ##### 11.5 - 11.6 ms: 91 ###### 11.6 - 11.7 ms: 87 ###### 11.7 - 11.8 ms: 55 #### 11.8 - 11.9 ms: 41 ### 11.9 - 12.0 ms: 36 ## 12.0 - 12.1 ms: 34 ## 12.1 - 12.2 ms: 44 ### 12.2 - 12.3 ms: 48 ### 12.3 - 12.4 ms: 33 ## 12.4 - 12.5 ms: 35 ## 12.5 - 12.6 ms: 30 ## 12.6 - 12.7 ms: 31 ## 12.7 - 12.8 ms: 18 # 12.8 - 12.9 ms: 31 ## 12.9 - 13.0 ms: 23 # 13.0 - 13.1 ms: 22 # 13.1 - 13.2 ms: 17 # 13.2 - 13.3 ms: 12 # 13.3 - 13.4 ms: 11 # 13.4 - 13.5 ms: 11 # 13.5 - 13.6 ms: 9 # 13.6 - 13.7 ms: 17 # 13.7 - 13.8 ms: 7 # 13.8 - 13.9 ms: 10 # 13.9 - 14.0 ms: 8 # 14.0 - 14.1 ms: 7 # 14.1 - 14.2 ms: 7 # 14.2 - 14.3 ms: 11 # ... 14.4 - 14.5 ms: 6 # 14.5 - 14.6 ms: 6 # 14.6 - 14.7 ms: 3 # 14.7 - 14.8 ms: 1 # ... 14.9 - 15.0 ms: 4 # ... 15.1 - 15.2 ms: 2 # 15.2 - 15.3 ms: 1 # ... 15.4 - 15.5 ms: 5 # 15.5 - 15.6 ms: 2 # 15.6 - 15.7 ms: 1 # 15.7 - 15.8 ms: 2 # 15.8 - 15.9 ms: 3 # ... 16.3 - 16.4 ms: 1 # ... 16.5 - 16.6 ms: 1 # 16.6 - 16.7 ms: 1 # ... 18.9 - 19.0 ms: 1 # ... 19.3 - 19.4 ms: 1 # ... 19.5 - 19.6 ms: 1 # ... 20.0 - 20.1 ms: 1 # 20.1 - 20.2 ms: 1 # ... 23.0 - 23.1 ms: 1 # ... 23.7 - 23.8 ms: 1 # best latency was 4.18 ms worst latency was 23.72 ms, which is too much. Please check: - if your hardware uses shared IRQs - `watch -n 1 cat /proc/interrupts` while running this test to see, which IRQs the OS is using for your midi hardware, - if you're running this test on a realtime OS - `uname -a` should contain '-rt', - your OS' scheduling priorities - `chrt -p [pidof process name|IRQ-?]`. Have a look at http://www.linuxaudio.org/mailarchive/lat/ to find out, howto fix issues with high midi latencies. ==== RESULTS WITHOUT PIANOBOOSTER ===== ./alsa-midi-latency-test -o 24:0 -i 24:0 -R -w 1 -r sched_setscheduler: Operation not permitted sample; latency_ms; latency_ms_worst 0; 3.69; 3.69 1; 3.80; 3.80 5; 4.82; 4.82 107; 6.17; 6.17 238; 6.30; 6.30 496; 6.52; 6.52 4712; 6.79; 6.79 8429; 6.82; 6.82 9999; 3.74; 6.82 ... 3.0 - 3.1 ms: 12 # 3.1 - 3.2 ms: 921 ############################################# 3.2 - 3.3 ms: 961 ############################################### 3.3 - 3.4 ms: 969 ############################################### 3.4 - 3.5 ms: 994 ################################################# 3.5 - 3.6 ms: 948 ############################################## 3.6 - 3.7 ms: 944 ############################################## 3.7 - 3.8 ms: 944 ############################################## 3.8 - 3.9 ms: 1022 ################################################## 3.9 - 4.0 ms: 981 ################################################ 4.0 - 4.1 ms: 966 ############################################### 4.1 - 4.2 ms: 137 ####### 4.2 - 4.3 ms: 22 # 4.3 - 4.4 ms: 18 # 4.4 - 4.5 ms: 22 # 4.5 - 4.6 ms: 14 # 4.6 - 4.7 ms: 10 # 4.7 - 4.8 ms: 11 # 4.8 - 4.9 ms: 16 # 4.9 - 5.0 ms: 7 # 5.0 - 5.1 ms: 9 # 5.1 - 5.2 ms: 14 # 5.2 - 5.3 ms: 9 # 5.3 - 5.4 ms: 3 # 5.4 - 5.5 ms: 7 # 5.5 - 5.6 ms: 5 # 5.6 - 5.7 ms: 4 # 5.7 - 5.8 ms: 4 # 5.8 - 5.9 ms: 6 # 5.9 - 6.0 ms: 3 # ... 6.1 - 6.2 ms: 2 # 6.2 - 6.3 ms: 7 # 6.3 - 6.4 ms: 2 # ... 6.5 - 6.6 ms: 1 # ... 6.7 - 6.8 ms: 3 # 6.8 - 6.9 ms: 2 # best latency was 3.04 ms worst latency was 6.82 ms, which is too much. Please check: