You are supposed to set your Sample Grabber up before connecting its input. Your request to make it 24-bit RGB is late and your actual connection and media type is different. You are still ignoring this on your callback and hence the broken picture.
Why i get bad image result from my webcamera?
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21-09-2022 - |
質問
I am getting wrong image result from SampleGrabber filter. Instead of colourfull image, image is in grayscale with red/green pixels between and image is repeated twice horizontaly.
I had to forget something important.
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();
}
}
}
This is my code. I enumerated all video devices. My device has ID 1. I created filter where webcam data is passed then i connected samplegrabber filter to the previous filter. Callback function is called when image is ready.
Unfortunately, image output is wrong and i have no idea why.
Also callback says bufferlen is 614 400 bytes. Strange as it means that pixel has only 16 bits. (640*480*2). Does it mean, buffer has different colorspace ? YUV ? Most examples does not care about color space and it's working fine. Also i specified RGB24 in mediaType.
Thank you very much for helping me.
解決