我们在实现Windows平台RTSP播放器或RTMP播放器的时候，需要考虑的点很多，比如多实例设计、多绘制模式兼容、软硬解码支持、快照、RTSP下TCP-UDP自动切换等，以下就其中几个方面，做个大概的探讨：
1. 视频绘制模式
我们在实现Windows平台播放的时候，一般首选D3D，D3D不支持的情况下，考虑数据回上来，采用GDI模式，一般实现如下，先做D3D检测，以大牛直播SDK播放端为例（Github），调用NT_SP_IsSupportD3DRender()，检测是否支持D3D模式，如果支持的话，调用NT_SP_SetRenderWindow(), 然后，设置是否等比例缩放（调用NT_SP_SetRenderScaleMode()）。
bool is_support_d3d_render = false;
Int32 in_support_d3d_render = 0;
if (NT.NTBaseCodeDefine.NT_ERC_OK == NTSmartPlayerSDK.NT_SP_IsSupportD3DRender(player_handle_, playWnd.Handle, ref in_support_d3d_render))
{
if (1 == in_support_d3d_render)
{
is_support_d3d_render = true;
}
}
if (is_support_d3d_render)
{
is_gdi_render_ = false;
// 支持d3d绘制的话，就用D3D绘制
NTSmartPlayerSDK.NT_SP_SetRenderWindow(player_handle_, playWnd.Handle);
if (btn_check_render_scale_mode.Checked)
{
NTSmartPlayerSDK.NT_SP_SetRenderScaleMode(player_handle_, 1);
}
else
{
NTSmartPlayerSDK.NT_SP_SetRenderScaleMode(player_handle_, 0);
}
}
else
{
is_gdi_render_ = true;
playWnd.Visible = false;
// 不支持D3D就让播放器吐出数据来，用GDI绘制
//video frame callback (YUV/RGB)
//format请参见 NT_SP_E_VIDEO_FRAME_FORMAT，如需回调YUV，请设置为 NT_SP_E_VIDEO_FRAME_FROMAT_I420
video_frame_call_back_ = new SP_SDKVideoFrameCallBack(SetVideoFrameCallBack);
NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FORMAT_RGB32, IntPtr.Zero, video_frame_call_back_);
}
如果不支持D3D，设置RGB数据回调：
video_frame_call_back_ = new SP_SDKVideoFrameCallBack(SetVideoFrameCallBack);
NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FORMAT_RGB32, IntPtr.Zero, video_frame_call_back_);
数据处理如下：
public void SetVideoFrameCallBack(IntPtr handle, IntPtr userData, UInt32 status, IntPtr frame)
{
if (frame == IntPtr.Zero)
{
return;
}
//如需直接处理RGB数据，请参考以下流程
NT_SP_VideoFrame video_frame = (NT_SP_VideoFrame)Marshal.PtrToStructure(frame, typeof(NT_SP_VideoFrame));
NT_SP_VideoFrame pVideoFrame = new NT_SP_VideoFrame();
pVideoFrame.format_ = video_frame.format_;
pVideoFrame.width_ = video_frame.width_;
pVideoFrame.height_ = video_frame.height_;
pVideoFrame.timestamp_ = video_frame.timestamp_;
pVideoFrame.stride0_ = video_frame.stride0_;
pVideoFrame.stride1_ = video_frame.stride1_;
pVideoFrame.stride2_ = video_frame.stride2_;
pVideoFrame.stride3_ = video_frame.stride3_;
Int32 argb_size = video_frame.stride0_ * video_frame.height_;
pVideoFrame.plane0_ = Marshal.AllocHGlobal(argb_size);
CopyMemory(pVideoFrame.plane0_, video_frame.plane0_, (UInt32)argb_size);
if (playWnd.InvokeRequired)
{
BeginInvoke(set_video_frame_call_back_, status, pVideoFrame);
}
else
{
set_video_frame_call_back_(status, pVideoFrame);
}
}在OnPaint()绘制即可：
private void SmartPlayerForm_Paint(object sender, PaintEventArgs e)
{
if (player_handle_ == IntPtr.Zero || !is_gdi_render_ || !is_playing_)
{
return;
}
if (cur_video_frame_.plane0_ == IntPtr.Zero)
{
return;
}
Bitmap bitmap = new Bitmap(cur_video_frame_.width_, cur_video_frame_.height_, cur_video_frame_.stride0_,
System.Drawing.Imaging.PixelFormat.Format32bppRgb, cur_video_frame_.plane0_);
int image_width = cur_video_frame_.width_;
int image_height = cur_video_frame_.height_;
Graphics g = e.Graphics; //获取窗体画布
g.SmoothingMode = SmoothingMode.HighSpeed;
int limit_w = this.Width - 60;
int limit_h = this.Height - playWnd.Top - 60;
if (btn_check_render_scale_mode.Checked)
{
int d_w = 0, d_h = 0;
int left_offset = 0;
int top_offset = 0;
Brush brush = new SolidBrush(Color.Black);
g.FillRectangle(brush, playWnd.Left, playWnd.Top, limit_w, limit_h);
GetRenderRect(limit_w, limit_h, image_width, image_height, ref left_offset, ref top_offset, ref d_w, ref d_h);
g.DrawImage(bitmap, playWnd.Left + left_offset, playWnd.Top + top_offset, d_w, d_h); //在窗体的画布中绘画出内存中的图像
}
else
{
g.DrawImage(bitmap, playWnd.Left, playWnd.Top, limit_w, limit_h); //在窗体的画布中绘画出内存中的图像
}
}2. 特定机型硬解码
Windows平台硬解码，主要适用于性能偏弱的PC端，或者有多路播放诉求的场景，一般建议在软解性能没问题的情况下，尽量软解，具体处理如下，先检测系统是否支持硬解，如果支持，再做硬解设置，这样的好处在于如果系统不支持硬解，可以继续软解播放，具体设置如下，在调用NT_SP_Open()之前，做检测，因为NT_SP_Open()每个句柄对应一个player实例，多个实例只需要做一次判断即可：
is_support_h264_hardware_decoder_ = NT.NTBaseCodeDefine.NT_ERC_OK == NT.NTSmartPlayerSDK.NT_SP_IsSupportH264HardwareDecoder();
is_support_h265_hardware_decoder_ = NT.NTBaseCodeDefine.NT_ERC_OK == NT.NTSmartPlayerSDK.NT_SP_IsSupportH265HardwareDecoder();
if (player_handle_ == IntPtr.Zero)
{
player_handle_ = new IntPtr();
UInt32 ret_open = NTSmartPlayerSDK.NT_SP_Open(out player_handle_, IntPtr.Zero, 0, IntPtr.Zero);
if (ret_open != 0)
{
player_handle_ = IntPtr.Zero;
MessageBox.Show("调用NT_SP_Open失败..");
return;
}
}播放之前，设置硬解码：
if (checkBox_hardware_decoder.Checked)
{
NTSmartPlayerSDK.NT_SP_SetH264HardwareDecoder(player_handle_, is_support_h264_hardware_decoder_ ? 1 : 0, 0);
NTSmartPlayerSDK.NT_SP_SetH265HardwareDecoder(player_handle_, is_support_h265_hardware_decoder_ ? 1 : 0, 0);
}
else
{
NTSmartPlayerSDK.NT_SP_SetH264HardwareDecoder(player_handle_, 0, 0);
NTSmartPlayerSDK.NT_SP_SetH265HardwareDecoder(player_handle_, 0, 0);
}3. 只解码关键帧
只解关键帧的场景，也是用于多路播放诉求，比如一般的监控场景，考虑到多路的场景，一般关键帧间隔不大（如1-2秒一个），平台可对现场场景有个宏观了解，如需重点关注某几路画面的时候，再实时取消这个选项，实现全帧播放，所以，只解关键帧一定要做成实时调用的接口才更有设计意义。
// 设置是否只解码关键帧
if (btn_check_only_decode_video_key_frame.Checked)
{
NTSmartPlayerSDK.NT_SP_SetOnlyDecodeVideoKeyFrame(player_handle_, 1);
}
else
{
NTSmartPlayerSDK.NT_SP_SetOnlyDecodeVideoKeyFrame(player_handle_, 0);
}4. 视频view旋转
好多现场的开发人员有这样的困惑，有些设备，在安装时，可能没调整好角度，导致拍出来的角度倒立等，看着很不方便，这时候，如果现场设备比较多的话，不可能每台设备都到现场重新安装，实时view旋转，就体现了价值，具体如下：
/*
* 设置旋转，顺时针旋转
* degress： 设置0， 90， 180， 270度有效，其他值无效
* 注意：除了0度，其他角度播放会耗费更多CPU
* 接口调用成功返回NT_ERC_OK
*/
[DllImport(@"SmartPlayerSDK.dll")]
public static extern UInt32 NT_SP_SetRotation(IntPtr handle, Int32 degress);视频view选择，会消耗一定的CPU。
5. 实时快照
实时快照功能不表，是一个好的RTSP播放器和RTMP播放器必备的功能，实时快照是把解码后的yuv数据重新编码成png，所以有一定的CPU消耗，不建议过于频繁操作，具体实现如下：
if ( String.IsNullOrEmpty(capture_image_path_) )
{
MessageBox.Show("请先设置保存截图文件的目录! 点击截图左边的按钮设置!");
return;
}
if ( player_handle_ == IntPtr.Zero )
{
return;
}
if ( !is_playing_)
{
MessageBox.Show("请在播放状态下截图!");
return;
}
String name = capture_image_path_ + "\" + DateTime.Now.ToString("hh-mm-ss") + ".png";
byte[] buffer1 = Encoding.Default.GetBytes(name);
byte[] buffer2 = Encoding.Convert(Encoding.Default, Encoding.UTF8, buffer1, 0, buffer1.Length);
byte[] buffer3 = new byte[buffer2.Length + 1];
buffer3[buffer2.Length] = 0;
Array.Copy(buffer2, buffer3, buffer2.Length);
IntPtr file_name_ptr = Marshal.AllocHGlobal(buffer3.Length);
Marshal.Copy(buffer3, 0, file_name_ptr, buffer3.Length);
capture_image_call_back_ = new SP_SDKCaptureImageCallBack(SDKCaptureImageCallBack);
UInt32 ret = NTSmartPlayerSDK.NT_SP_CaptureImage(player_handle_, file_name_ptr, IntPtr.Zero, capture_image_call_back_);
Marshal.FreeHGlobal(file_name_ptr);
if (NT.NTBaseCodeDefine.NT_ERC_OK == ret)
{
// 发送截图请求成功
}
else if ((UInt32)NT.NTSmartPlayerDefine.SP_E_ERROR_CODE.NT_ERC_SP_TOO_MANY_CAPTURE_IMAGE_REQUESTS == ret)
{
// 通知用户延时
MessageBox.Show("Too many capture image requests!");
}
else
{
// 其他失败
} public void SDKCaptureImageCallBack(IntPtr handle, IntPtr userData, UInt32 result, IntPtr file_name)
{
if (file_name == IntPtr.Zero)
return;
int index = 0;
while (true)
{
if (0 == Marshal.ReadByte(file_name, index))
break;
index++;
}
byte[] file_name_buffer = new byte[index];
Marshal.Copy(file_name, file_name_buffer, 0, index);
byte[] dst_buffer = Encoding.Convert(Encoding.UTF8, Encoding.Default, file_name_buffer, 0, file_name_buffer.Length);
String image_name = Encoding.Default.GetString(dst_buffer, 0, dst_buffer.Length);
if (playWnd.InvokeRequired)
{
BeginInvoke(set_capture_image_call_back_, result, image_name);
}
else
{
set_capture_image_call_back_(result, image_name);
}
}后续，我们将针对RTSP和RTMP播放器设计过程中的其他点，做更进一步的探讨。