iPad2上的CVOpenGLESTextureCacheCreateTextureFromImage太慢了,它需要差不多30毫秒,太疯了

Question

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,

- (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,

[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样本类似,包括着色器.所以我想知道为什么,如何解决这个问题.

Answer 1

随着我在这一天的研究,我发现为什么CVOpenGLESTextureCacheCreateTextureFromImage花费很多时间,当数据很大时,这里是3M,分配,复制和移动操作的成本相当可观,尤其是复制操作.然后用像素缓冲池大大提高性能CVOpenGLESTextureCacheCreateTextureFromImage从30ms到5ms,与glTexImage2D()的级别相同.我的解决方案如下:

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,您可以快速完成.

将以下配置添加到attribtes可以使其性能达到最佳,小于1ms.

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

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