为什么要支持GDI
先说结论,Windows平台播放渲染这块,一般来说99%以上的机器都是支持D3D的,实现GDI模式绘制,除了为了好的兼容性外,在远程连接的场景下,D3D创建不成功,需要使用GDI模式。
简单来说,Windows平台的RTMP播放器或RTSP播放器,设计如果系统支持D3D,优先D3D,如果检测到不支持D3D,数据回调上来,GDI模式绘制。
在之前的博客,我们提到过:D3D绘制出来的图像效果更细腻,绘制效率也更高,CPU占用相对GDI更低。
上图以1920*1080分辨率、30帧、固定码率(采集屏幕左侧区域)为例,通过大牛直播SDK ( github) 的Windows平台SmartPublisherDemo.exe工具推送到内网nginx服务器,然后分别以D3D模式和GDI模式拉流(播放端缓冲设置为0)。
可以看到:
D3D模式,CPU占用只有2.7%,延迟:249-156 = 93ms;
GDI模式,CPU占用19.5%,延迟249-73 = 176ms。
无论是从延迟和CPU占用上看,D3D模式都占优。
实现思路:
以C++的demo为例:
1. 先检测系统是否支持D3D模式:
if ( NT_ERC_OK == player_api_.IsSupportD3DRender(player_handle_,
wrapper_render_wnd_.RenderWnd(), &in_support_d3d_render))
{
if ( 1 == in_support_d3d_render )
{
is_support_d3d_render = true;
}
}
2. 如不支持D3D,数据回到上层,做绘制:
if ( is_support_d3d_render )
{
is_gdi_render_ = false;
// 支持d3d绘制的话,就用D3D绘制
player_api_.SetRenderWindow(player_handle_, wrapper_render_wnd_.RenderWnd());
player_api_.SetRenderScaleMode(player_handle_, btn_check_render_scale_mode_.GetCheck() == BST_CHECKED ? 1 : 0);
}
else
{
is_gdi_render_ = true;
// 不支持D3D就让播放器吐出数据来,用GDI绘制
wrapper_render_wnd_.SetRenderScaleMode(btn_check_render_scale_mode_.GetCheck() == BST_CHECKED ? 1 : 0);
player_api_.SetVideoFrameCallBack(player_handle_, NT_SP_E_VIDEO_FRAME_FORMAT_RGB32,
GetSafeHwnd(), SM_SDKVideoFrameHandle);
}
extern "C" NT_VOID NT_CALLBACK SM_SDKVideoFrameHandle(NT_HANDLE handle, NT_PVOID userData, NT_UINT32 status,
const NT_SP_VideoFrame* frame)
{
/*if (frame != NULL)
{
std::ostringstream ss;
ss << "Receive frame time_stamp:" << frame->timestamp_ << "ms" << "\r\n";
OutputDebugStringA(ss.str().c_str());
}*/
if ( frame != NULL )
{
if ( NT_SP_E_VIDEO_FRAME_FORMAT_RGB32 == frame->format_
&& frame->plane0_ != NULL
&& frame->stride0_ > 0
&& frame->height_ > 0 )
{
std::unique_ptr<nt_rgb32_image > pImage(new nt_rgb32_image());
pImage->size_ = frame->stride0_* frame->height_;
pImage->data_ = new NT_BYTE[pImage->size_];
memcpy(pImage->data_, frame->plane0_, pImage->size_);
pImage->width_ = frame->width_;
pImage->height_ = frame->height_;
pImage->stride_ = frame->stride0_;
HWND hwnd = (HWND)userData;
if ( hwnd != NULL && ::IsWindow(hwnd) )
{
::PostMessage(hwnd, WM_USER_SDK_RGB32_IMAGE, (WPARAM)handle, (LPARAM)pImage.release());
}
}
}
}
具体绘制代码:
LRESULT CSmartPlayerDlg::OnSDKRGB32Image(WPARAM wParam, LPARAM lParam)
{
nt_rgb32_image* pImage = (nt_rgb32_image*)(lParam);
if (pImage == NULL)
return S_OK;
std::shared_ptr<nt_rgb32_image> sp_image(pImage);
if ( is_gdi_render_ )
{
wrapper_render_wnd_.OnRGB32Image(sp_image);
}
return S_OK;
}
void nt_render_wnd::OnPaint()
{
CPaintDC dc(this); // device context for painting
// TODO: Add your message handler code here
// Do not call CWnd::OnPaint() for painting messages
if ( IsIconic() )
{
return;
}
// 先绘制一个黑色的背景
CRect rc_client(0, 0, 0, 0);
GetClientRect(rc_client);
if ( rc_client.IsRectNull()
|| rc_client.IsRectEmpty() )
{
return;
}
auto mem_dc = ::CreateCompatibleDC(dc.GetSafeHdc());
if ( mem_dc == NULL )
return;
auto mem_bitmap = ::CreateCompatibleBitmap(dc.GetSafeHdc(), rc_client.Width(), rc_client.Height());
if ( mem_bitmap == NULL )
{
::DeleteDC(mem_dc);
return;
}
::SelectObject(mem_dc, mem_bitmap);
HBRUSH brush = ::CreateSolidBrush(RGB(0, 0, 0));
::FillRect(mem_dc, &rc_client, brush);
::DeleteObject(brush);
if ( rgb32_image_ )
{
if ( player_api_.GDIDrawRGB32 != NULL
&& player_handle_ != NULL )
{
auto render_rc = GetRenderRect(rc_client, rgb32_image_->width_, rgb32_image_->height_);
player_api_.GDIDrawRGB32(player_handle_, mem_dc,
render_rc.left, render_rc.top,
render_rc.Width(), render_rc.Height(),
0, 0,
rgb32_image_->width_, rgb32_image_->height_,
rgb32_image_->data_, rgb32_image_->size_,
rgb32_image_->width_, rgb32_image_->height_,
rgb32_image_->stride_);
if (logo_ && logo_->data_ != nullptr)
{
player_api_.GDIDrawARGB(mem_dc,
render_logo_left_, render_logo_top_,
render_logo_width_, render_logo_height_,
0, 0,
logo_->width_, logo_->height_,
logo_->data_.get(), logo_->stride_,
logo_->width_, logo_->height_
);
}
}
}
::BitBlt(dc.GetSafeHdc(),
0, 0,
rc_client.Width(), rc_client.Height(),
mem_dc,
0, 0,
SRCCOPY);
::DeleteObject(mem_bitmap);
::DeleteDC(mem_dc);
}
目前来看,不支持D3D的机器少之又少,在环境具备的情况下,优先建议考虑D3D模式绘制,不支持的情况下,同时兼容GDI绘制是个不错的选择。