Question

我从SampleGrabber过滤器得到错误的图像结果。而不是彩色图像，图像是灰度的，红色/绿色像素介于两者之间，图像重复两次。

我不得不忘记重要的事情。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using DirectShowLib;
using System.Runtime.InteropServices;
using System.Drawing.Imaging;

namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        public IGraphBuilder gb;
        public ICaptureGraphBuilder2 cgb;
        public IBaseFilter filter;
        static SampleGrabberCallback cb;
        VideoInfoHeader header;
        static Form1 thisform;

        public class SampleGrabberCallback : ISampleGrabberCB
        {

            int ISampleGrabberCB.SampleCB(Double SampleTime, IMediaSample sample)
            {
                return 0;
            }

            int ISampleGrabberCB.BufferCB(Double SampleTime, IntPtr dataPtr, Int32 BufferLen)
            {
                Bitmap bitmap = new Bitmap(640, 480, 640 * 3, PixelFormat.Format24bppRgb, dataPtr);

                Graphics g = thisform.panel1.CreateGraphics();
                g.DrawImageUnscaled(bitmap, 0, 0, 640, 480);

                return 0;
            }
        }

        public Form1()
        {
            InitializeComponent();
            thisform = this;

            DsDevice[] videoInputDevices = DsDevice.GetDevicesOfCat(FilterCategory.VideoInputDevice);
            object obj = null; Guid iid = typeof(IBaseFilter).GUID;
            videoInputDevices[1].Mon.BindToObject(null, null, ref iid, out obj);
            filter = (IBaseFilter)obj;
            ISampleGrabber grabberFilter = (ISampleGrabber)new SampleGrabber();
            IBaseFilter baseGrabber = (IBaseFilter)grabberFilter;

            ((IAMCameraControl)filter).Set(CameraControlProperty.Exposure, 0, CameraControlFlags.Auto);

            gb = (IGraphBuilder)new FilterGraph();
            cgb = (ICaptureGraphBuilder2)new CaptureGraphBuilder2();

            cgb.SetFiltergraph(gb);

            IEnumPins pins;
            IPin[] inputPin = { null };
            IPin[] outputPin = { null };

            filter.EnumPins(out pins);
            pins.Next(1, outputPin, IntPtr.Zero);

            baseGrabber.EnumPins(out pins);
            pins.Next(1, inputPin, IntPtr.Zero);

            gb.AddFilter(filter, "First Filter");
            gb.AddFilter(baseGrabber, "Grabber Filter");
            gb.Connect(outputPin[0], inputPin[0]);

            grabberFilter.SetBufferSamples(true);

            AMMediaType media = new AMMediaType();
            media.majorType = MediaType.Video;
            media.subType = MediaSubType.RGB24;
            media.formatPtr = IntPtr.Zero;

            grabberFilter.SetMediaType(media);
            grabberFilter.GetConnectedMediaType(media);
            header = (VideoInfoHeader)Marshal.PtrToStructure(media.formatPtr, typeof(VideoInfoHeader));

            cb = new SampleGrabberCallback();

            grabberFilter.SetCallback(cb, 1);

            cgb.RenderStream(PinCategory.Preview, MediaType.Video, filter, null, null);
            ((IMediaControl)gb).Run();
        }
    }
}

这是我的代码。我列举了所有视频设备。我的设备有ID 1.我创建了过滤器，其中传递了网络摄像头数据，然后我将samplegrabber过滤器连接到前一个过滤器。图像准备就绪时调用回调函数。

不幸的是，图像输出错误，我不明白为什么。

同样回调说缓冲区是614 400字节。奇怪，因为它意味着像素只有16位。（640 * 480 * 2）。这是不是意味着，缓冲区有不同的色彩空间？ YUV？大多数例子都不关心色彩空间，它的工作正常。我还在mediaType中指定了RGB24。

非常感谢你帮助我。

Answer 1

您应该在连接输入之前设置Sample Grabber。您使其成为24位RGB的请求很晚，您的实际连接和媒体类型也不同。你仍然在你的回调中忽略了这一点，因此破碎的画面。

为什么我的网络摄像头会导致图像效果不佳？

1 个答案: