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Re: [pygame] Noticeable lag between key press events and sound events



Thank you for your replies: Dan, Greg, Inigo, and Ian

I changed the sound buffer size and it helped a lot. I verified that there was no empty space in the loop with Audacity. I changed the program to queue the next sound on the key press events and play the queued sound when the previous sound ends. This way there is less chance for weird uneven drum loops. My long term goal is to replace the key press events with Midi events.

Here is my updated code ( from the terminal "export SDL_AUDIODRIVER=pulse && python -u sampler.py")

#----------------------------------------------------------
import pygame
from pygame.locals import *
from sys import exit

pygame.mixer.pre_init(44100,-16,2,2048)
pygame.init()

#pygame.mixer.set_reserved(1)
reserved_channel_0 = pygame.mixer.Channel(0)
sound1 = pygame.mixer.Sound("beat1.wav")
sound2 = pygame.mixer.Sound("beat2.wav")
sound3 = pygame.mixer.Sound("beat3.wav")
sound4 = pygame.mixer.Sound("beat4.wav")

green = (138,226,52)
blue = (114,159,207)
black = (46,52,54)
white = (238,238,236)

pygame.display.set_caption("badp3nn1 sampler")

my_font = pygame.font.SysFont("Arial",32)

SCREEN_SIZE = (400, 300)
screen = pygame.display.set_mode(SCREEN_SIZE, RESIZABLE, 32)

TRACK_END = USEREVENT + 1
reserved_channel_0.set_endevent(TRACK_END)

def updateScreenAndQueueNextSound():
        if reserved_channel_0.get_busy() == False:
                print "Channel is not busy"
                reserved_channel_0.queue(nextsound)
        screen.fill(blue)
        screen.blit(my_font.render("Change Queued",True,white),(0,0) )
        pygame.display.update()


while True:
        for event in pygame.event.get():
                if event.type == KEYDOWN:
                        if event.key == K_UP:
                                nextsound = sound1
                                updateScreenAndQueueNextSound()

                        elif event.key == K_DOWN:
                                nextsound = sound2
                                updateScreenAndQueueNextSound()

                        elif event.key == K_LEFT:
                                nextsound = sound3
                                updateScreenAndQueueNextSound()

                        elif event.key == K_RIGHT:
                                nextsound = sound4
                                updateScreenAndQueueNextSound()

                elif event.type == TRACK_END:
                        reserved_channel_0.queue(nextsound)
                        screen.fill(green)
                        screen.blit(my_font.render("Looping",True,black),(0,0) )
                        pygame.display.update()

                elif event.type == QUIT:
                        exit()


#----------------------------------------------------------


 

On Sun, Dec 12, 2010 at 6:34 PM, Greg Ewing <greg.ewing@xxxxxxxxxxxxxxxx> wrote:
Brian Gryder wrote:

There is a noticeable lag between the key press events and the sound changes.

Have you tried reducing the size of the sound buffer? It seems
that the pygame mixer can only start a sound on a buffer
boundary, so for accurate sound timing you need quite a small
buffer size.

--
Greg