diff options
Diffstat (limited to 'pd/portmidi/pm_test/latency.c')
| -rw-r--r-- | pd/portmidi/pm_test/latency.c | 278 |
1 files changed, 0 insertions, 278 deletions
diff --git a/pd/portmidi/pm_test/latency.c b/pd/portmidi/pm_test/latency.c deleted file mode 100644 index 87b1965b..00000000 --- a/pd/portmidi/pm_test/latency.c +++ /dev/null @@ -1,278 +0,0 @@ -/* latency.c -- measure latency of OS */
-
-#include "porttime.h"
-#include "portmidi.h"
-#include "stdlib.h"
-#include "stdio.h"
-#include "string.h"
-#include "assert.h"
-
-/* Latency is defined here to mean the time starting when a
- process becomes ready to run, and ending when the process
- actually runs. Latency is due to contention for the
- processor, usually due to other processes, OS activity
- including device drivers handling interrupts, and
- waiting for the scheduler to suspend the currently running
- process and activate the one that is waiting.
-
- Latency can affect PortMidi applications: if a process fails
- to wake up promptly, MIDI input may sit in the input buffer
- waiting to be handled, and MIDI output may not be generated
- with accurate timing. Using the latency parameter when
- opening a MIDI output port allows the caller to defer timing
- to PortMidi, which in most implementations will pass the
- data on to the OS. By passing timestamps and data to the
- OS kernel, device driver, or even hardware, there are fewer
- sources of latency that can affect the ultimate timing of
- the data. On the other hand, the application must generate
- and deliver the data ahead of the timestamp. The amount by
- which data is computed early must be at least as large as
- the worst-case latency to avoid timing problems.
-
- Latency is even more important in audio applications. If an
- application lets an audio output buffer underflow, an audible
- pop or click is produced. Audio input buffers can overflow,
- causing data to be lost. In general the audio buffers must
- be large enough to buffer the worst-case latency that the
- application will encounter.
-
- This program measures latency by recording the difference
- between the scheduled callback time and the current real time.
- We do not really know the scheduled callback time, so we will
- record the differences between the real time of each callback
- and the real time of the previous callback. Differences that
- are larger than the scheduled difference are recorded. Smaller
- differences indicate the system is recovering from an earlier
- latency, so these are ignored.
- Since printing by the callback process can cause all sorts of
- delays, this program records latency observations in a
- histogram. When the program is stopped, the histogram is
- printed to the console.
-
- Optionally the system can be tested under a load of MIDI input,
- MIDI output, or both. If MIDI input is selected, the callback
- thread will read any waiting MIDI events each iteration. You
- must generate events on this interface for the test to actually
- put any appreciable load on PortMidi. If MIDI output is
- selected, alternating note on and note off events are sent each
- X iterations, where you specify X. For example, with a timer
- callback period of 2ms and X=1, a MIDI event is sent every 2ms.
-
-
- INTERPRETING RESULTS: Time is quantized to 1ms, so there is
- some uncertainty due to rounding. A microsecond latency that
- spans the time when the clock is incremented will be reported
- as a latency of 1. On the other hand, a latency of almost
- 1ms that falls between two clock ticks will be reported as
- zero. In general, if the highest nonzero bin is numbered N,
- then the maximum latency is N+1.
-
-CHANGE LOG
-
-18-Jul-03 Mark Nelson -- Added code to generate MIDI or receive
- MIDI during test, and made period user-settable.
- */
-
-#define HIST_LEN 21 /* how many 1ms bins in the histogram */
-
-#define STRING_MAX 80 /* used for console input */
-
-#define INPUT_BUFFER_SIZE 100
-#define OUTPUT_BUFFER_SIZE 0
-
-#ifndef max
-#define max(a, b) ((a) > (b) ? (a) : (b))
-#endif
-#ifndef min
-#define min(a, b) ((a) <= (b) ? (a) : (b))
-#endif
-
-int get_number(char *prompt);
-
-PtTimestamp previous_callback_time = 0;
-
-int period; /* milliseconds per callback */
-
-long histogram[HIST_LEN];
-long max_latency = 0; /* worst latency observed */
-long out_of_range = 0; /* how many points outside of HIST_LEN? */
-
-int test_in, test_out; /* test MIDI in and/or out? */
-int output_period; /* output MIDI every __ iterations if test_out true */
-int iteration = 0;
-PmStream *in, *out;
-int note_on = 0; /* is the note currently on? */
-
-/* callback function for PortTime -- computes histogram */
-void pt_callback(PtTimestamp timestamp, void *userData)
-{
- PtTimestamp difference = timestamp - previous_callback_time - period;
- previous_callback_time = timestamp;
-
- /* allow 5 seconds for the system to settle down */
- if (timestamp < 5000) return;
-
- iteration++;
- /* send a note on/off if user requested it */
- if (test_out && (iteration % output_period == 0)) {
- PmEvent buffer[1];
- buffer[0].timestamp = Pt_Time(NULL);
- if (note_on) {
- /* note off */
- buffer[0].message = Pm_Message(0x90, 60, 0);
- note_on = 0;
- } else {
- /* note on */
- buffer[0].message = Pm_Message(0x90, 60, 100);
- note_on = 1;
- }
- Pm_Write(out, buffer, 1);
- iteration = 0;
- }
-
- /* read all waiting events (if user requested) */
- if (test_in) {
- PmError status;
- PmEvent buffer[1];
- do {
- status = Pm_Poll(in);
- if (status == TRUE) {
- Pm_Read(in,buffer,1);
- }
- } while (status == TRUE);
- }
-
- if (difference < 0) return; /* ignore when system is "catching up" */
-
- /* update the histogram */
- if (difference < HIST_LEN) {
- histogram[difference]++;
- } else {
- out_of_range++;
- }
-
- if (max_latency < difference) max_latency = difference;
-}
-
-
-int main()
-{
- char line[STRING_MAX];
- int i;
- int len;
- int choice;
- PtTimestamp stop;
- printf("Latency histogram.\n");
- period = get_number("Choose timer period (in ms): ");
- assert(period >= 1);
- printf("Benchmark with:\n\t%s\n\t%s\n\t%s\n\t%s\n",
- "1. No MIDI traffic",
- "2. MIDI input",
- "3. MIDI output",
- "4. MIDI input and output");
- choice = get_number("? ");
- switch (choice) {
- case 1: test_in = 0; test_out = 0; break;
- case 2: test_in = 1; test_out = 0; break;
- case 3: test_in = 0; test_out = 1; break;
- case 4: test_in = 1; test_out = 1; break;
- default: assert(0);
- }
- if (test_in || test_out) {
- /* list device information */
- for (i = 0; i < Pm_CountDevices(); i++) {
- const PmDeviceInfo *info = Pm_GetDeviceInfo(i);
- if ((test_in && info->input) ||
- (test_out && info->output)) {
- printf("%d: %s, %s", i, info->interf, info->name);
- if (info->input) printf(" (input)");
- if (info->output) printf(" (output)");
- printf("\n");
- }
- }
- /* open stream(s) */
- if (test_in) {
- int i = get_number("MIDI input device number: ");
- Pm_OpenInput(&in,
- i,
- NULL,
- INPUT_BUFFER_SIZE,
- (long (*)(void *)) Pt_Time,
- NULL);
- /* turn on filtering; otherwise, input might overflow in the
- 5-second period before timer callback starts reading midi */
- Pm_SetFilter(in, PM_FILT_ACTIVE | PM_FILT_CLOCK);
- }
- if (test_out) {
- int i = get_number("MIDI output device number: ");
- PmEvent buffer[1];
- Pm_OpenOutput(&out,
- i,
- NULL,
- OUTPUT_BUFFER_SIZE,
- (long (*)(void *)) Pt_Time,
- NULL,
- 0); /* no latency scheduling */
-
- /* send a program change to force a status byte -- this fixes
- a problem with a buggy linux MidiSport driver, and shouldn't
- hurt anything else
- */
- buffer[0].timestamp = 0;
- buffer[0].message = Pm_Message(0xC0, 0, 0); /* program change */
- Pm_Write(out, buffer, 1);
-
- output_period = get_number(
- "MIDI out should be sent every __ callback iterations: ");
-
- assert(output_period >= 1);
- }
- }
-
- printf("%s%s", "Latency measurements will start in 5 seconds. ",
- "Type return to stop: ");
- Pt_Start(period, &pt_callback, 0);
- fgets(line, STRING_MAX, stdin);
- stop = Pt_Time();
- Pt_Stop();
-
- /* courteously turn off the last note, if necessary */
- if (note_on) {
- PmEvent buffer[1];
- buffer[0].timestamp = Pt_Time(NULL);
- buffer[0].message = Pm_Message(0x90, 60, 0);
- Pm_Write(out, buffer, 1);
- }
-
- /* print the histogram */
- printf("Duration of test: %g seconds\n\n", max(0, stop - 5000) * 0.001);
- printf("Latency(ms) Number of occurrences\n");
- /* avoid printing beyond last non-zero histogram entry */
- len = min(HIST_LEN, max_latency + 1);
- for (i = 0; i < len; i++) {
- printf("%2d %10ld\n", i, histogram[i]);
- }
- printf("Number of points greater than %dms: %ld\n",
- HIST_LEN - 1, out_of_range);
- printf("Maximum latency: %ld milliseconds\n", max_latency);
- printf("\nNote that due to rounding, actual latency can be 1ms higher\n");
- printf("than the numbers reported here.\n");
- printf("Type return to exit...");
- fgets(line, STRING_MAX, stdin);
- return 0;
-}
-
-
-/* read a number from console */
-int get_number(char *prompt)
-{
- char line[STRING_MAX];
- int n = 0, i;
- printf(prompt);
- while (n != 1) {
- n = scanf("%d", &i);
- fgets(line, STRING_MAX, stdin);
-
- }
- return i;
-}
|