iPad2上的CVOpenGLESTextureCacheCreateTextureFromImage太慢了，它需要差不多30毫秒，太疯了 [英] CVOpenGLESTextureCacheCreateTextureFromImage on iPad2 is too slow ,it needs almost 30 ms, too crazy

问题描述

我使用opengl es在iPad上显示bgr24数据，我是关于opengl es的新手，所以在显示视频部分我使用来自RosyWriter的代码一个APPLE样本。它可以工作，但CVOpenGLESTextureCacheCreateTextureFromImage函数的成本超过30毫秒，而在RosyWriter
中它的成本可以忽略不计。
我所做的是先将BGR24转换为BGRA像素格式，然后使用CVPixelBufferCreateWithBytes函数创建一个CVPixelBufferRef，然后通过CVOpenGLESTextureCacheCreateTextureFromImage获取CVOpenGLESTextureRef。我的代码如下，

I use opengl es to display bgr24 data on iPad, I am new about opengl es ,so in display video part I use code from RosyWriter one APPLE sample. It works, but the CVOpenGLESTextureCacheCreateTextureFromImage function cost more than 30ms, while in RosyWriter its cost is negligible. what I do is first transform BGR24 to BGRA pixel format, then use CVPixelBufferCreateWithBytes function create a CVPixelBufferRef, and then get a CVOpenGLESTextureRef by CVOpenGLESTextureCacheCreateTextureFromImage. My codes as following,

- (void)transformBGRToBGRA:(const UInt8 *)pict width:(int)width height:(int)height
{
rgb.data = (void *)pict;

vImage_Error error = vImageConvert_RGB888toARGB8888(&rgb,NULL,0,&argb,NO,kvImageNoFlags);
if (error != kvImageNoError) {
    NSLog(@"vImageConvert_RGB888toARGB8888 error");
}

const uint8_t permuteMap[4] = {1,2,3,0};

error = vImagePermuteChannels_ARGB8888(&argb,&bgra,permuteMap,kvImageNoFlags);
if (error != kvImageNoError) {
    NSLog(@"vImagePermuteChannels_ARGB8888 error");
}

free((void *)pict);
}

并且在变换之后，将生成CVPixelBufferRef，代码如下，

and after transform, will generate CVPixelBufferRef, codes as following,

[self transformBGRToBGRA:pict width:width height:height];

CVPixelBufferRef pixelBuffer;
CVReturn err = CVPixelBufferCreateWithBytes(NULL,
                             width,
                             height,
                             kCVPixelFormatType_32BGRA, 
                             (void*)bgraData, 
                             bytesByRow, 
                             NULL, 
                             0,
                             NULL, 
                             &pixelBuffer);

if(!pixelBuffer || err)
{
    NSLog(@"CVPixelBufferCreateWithBytes failed (error: %d)", err);  
    return;
}

CVOpenGLESTextureRef texture = NULL;
err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, 
                                                            videoTextureCache,
                                                            pixelBuffer,
                                                            NULL,
                                                            GL_TEXTURE_2D,
                                                            GL_RGBA,
                                                            width,
                                                            height,
                                                            GL_BGRA,
                                                            GL_UNSIGNED_BYTE,
                                                            0,
                                                            &texture);


if (!texture || err) {
    NSLog(@"CVOpenGLESTextureCacheCreateTextureFromImage failed (error: %d)", err);  
    CVPixelBufferRelease(pixelBuffer);
    return;
}

其他代码几乎与RosyWriter示例类似，包括着色器。所以我想知道为什么，
如何解决这个问题。

The other codes is almost similar RosyWriter sample, include shaders. So I want to know why, how to fix this problem.

推荐答案

凭借我在这一天的研究，我找到原因 CVOpenGLESTextureCacheCreateTextureFromImage 花费很多时间，当数据很大时，这里是3M，分配，复制和移动操作哪个成本相当可观，特别是复制操作。然后使用像素缓冲池大大提高 CVOpenGLESTextureCacheCreateTextureFromImage 的性能，从30ms到5ms，与glTexImage2D（）的级别相同。我的解决方案如下：

With my research in these day, I find why CVOpenGLESTextureCacheCreateTextureFromImage cost much time, when the data is big, here is 3M, the allocation, copy and move operation which cost is considerable, especially Copy operation. Then with pixel buffer pool greatly improve performance of CVOpenGLESTextureCacheCreateTextureFromImage from 30ms to 5ms, the same level with glTexImage2D(). My solution as following:

NSMutableDictionary*     attributes;
attributes = [NSMutableDictionary dictionary];


[attributes setObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(NSString*)kCVPixelBufferPixelFormatTypeKey];
[attributes setObject:[NSNumber numberWithInt:videoWidth] forKey: (NSString*)kCVPixelBufferWidthKey];
[attributes setObject:[NSNumber numberWithInt:videoHeight] forKey: (NSString*)kCVPixelBufferHeightKey];

CVPixelBufferPoolCreate(kCFAllocatorDefault, NULL, (CFDictionaryRef) attributes, &bufferPool);

CVPixelBufferPoolCreatePixelBuffer (NULL,bufferPool,&pixelBuffer);

CVPixelBufferLockBaseAddress(pixelBuffer,0);

UInt8 * baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer);

memcpy(baseAddress, bgraData, bytesByRow * videoHeight);

CVPixelBufferUnlockBaseAddress(pixelBuffer,0);

使用这个新创建的 pixelBuffer ，你可以加快速度。

with this new created pixelBuffer you can make it fast.

将以下配置添加到 attribtes 可以使其性能达到最佳，不到1毫秒。

Add following configures to attribtes can make its performance to the best, less than 1ms.

 NSDictionary *IOSurfaceProperties = [NSDictionary dictionaryWithObjectsAndKeys:
                                                                        [NSNumber numberWithBool:YES], @"IOSurfaceOpenGLESFBOCompatibility",[NSNumber numberWithBool:YES], @"IOSurfaceOpenGLESTextureCompatibility",nil];

[attributes setObject:IOSurfaceProperties forKey:(NSString*)kCVPixelBufferIOSurfacePropertiesKey];

这篇关于iPad2上的CVOpenGLESTextureCacheCreateTextureFromImage太慢了，它需要差不多30毫秒，太疯了的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！