Blitted OpenGL Textures take less memory and CPU - opengl

Question

I'm making a game using pygame + pyopengl, and right now i'm trying to make a video player on this context. To do so I use ffmpeg to load different video formats, then convert each frame to an opengl texture, as designed below, and then play the video.
class Texture(object):
def __init__(self, data, w=0, h=0):
"""
Initialize the texture from 3 diferents types of data:
filename = open the image, get its string and produce texture
surface = get its string and produce texture
string surface = gets it texture and use w and h provided
"""
if type(data) == str:
texture_data = self.load_image(data)
elif type(data) == pygame.Surface:
texture_data = pygame.image.tostring(data, "RGBA", True)
self.w, self.h = data.get_size()
elif type(data) == bytes:
self.w, self.h = w, h
texture_data = data
self.texID = 0
self.load_texture(texture_data)
def load_image(self, data):
texture_surface = pygame.image.load(data).convert_alpha()
texture_data = pygame.image.tostring(texture_surface, "RGBA", True)
self.w, self.h = texture_surface.get_size()
return texture_data
def load_texture(self, texture_data):
self.texID = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, self.texID)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, self.w,
self.h, 0, GL_RGBA, GL_UNSIGNED_BYTE,
texture_data)
Problem is that when i load all the textures of a given video, my RAM goes off the ceiling, about 800mb. But it's possible to work around this by blitting each texture as it loads, like shown below.
def render():
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
glLoadIdentity()
glDisable(GL_LIGHTING)
glEnable(GL_TEXTURE_2D)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
glClearColor(0, 0, 0, 1.0)
def Draw(texture, top, left, bottom, right):
"""
Draw the image on the Opengl Screen
"""
# Make sure he is looking at the position (0,0,0)
glBindTexture(GL_TEXTURE_2D, texture.texID)
glBegin(GL_QUADS)
# The top left of the image must be the indicated position
glTexCoord2f(0.0, 1.0)
glVertex2f(left, top)
glTexCoord2f(1.0, 1.0)
glVertex2f(right, top)
glTexCoord2f(1.0, 0.0)
glVertex2f(right, bottom)
glTexCoord2f(0.0, 0.0)
glVertex2f(left, bottom)
glEnd()
def update(t):
render()
Draw(t, -0.5, -0.5, 0.5, 0.5)
# Check for basic Events on the pygame interface
for event in pygame.event.get():
BASIC_Game.QUIT_Event(event)
pygame.display.flip()
Although this reduces the RAM consumption to an acceptable value it makes the loading time bigger than the video length.
I really don't understand why opengl works this way, but is there a way to make a texture efficient without blitting it first?

Answer 1

I can't tell for sure based off the code you have in your question right now, but I'm going to guess it's because you're creating a new Texture instance for each frame, which means that you're calling glGenTextures(1) for every frame of your video. This allocates a new buffer in memory for every frame of your video, and then stores a full, uncompressed version of the frame.
When you blit the image, you're not generating a new texture, but just overwriting the old one. This is the solution you want, but the way you're implementing it is inefficient.
There are a number of ways you can change the data in a texture without blitting on the CPU (assuming pygame blitting) to make things go faster, some are listed in this answer:
https://stackoverflow.com/a/13248668/1122135