Develop Reference

Resampling WasapiLoopbackCapture

I'm trying to resample the WasapiLoopbackCapture's output from my soundcards 44100Hz, 16bit, 2 channel waveformat to a 16000Hz, 16bit, 1 channel format for later use in a System.Net.Sockets.NetworkStream (I want to write the converted bytes to the network stream)
But I have no idea how to start even!
I'm really new to signal processing and I've tried searching for tutorials but I just can't wrap my head around how to do this.
Here's what I got so far:
void StartRecording()
{
capture = new WasapiLoopbackCapture(device); // device is an audiodevice picked from the user. speaker, headphones etc
capture.ShareMode = NAudio.CoreAudioApi.AudioClientShareMode.Shared;
capture.DataAvailable += capture_DataAvailable;
capture.RecordingStopped += capture_RecordingStopped;
capture.StartRecording();
}
void capture_DataAvailable(object sender, WaveInEventArgs e)
{
outputStream.Write(e.Buffer, 0, e.BytesRecorded); // here I want to output audio to the NetworkStream.
// But I have to resample it first, which brings me to my question.
}
What I basically want to know is how I can get a byte-array which has been resampled and ready to be shipped off to the other side of the networkstream!
Any suggestions are really appreciated! Thank you in advance.

NAudio includes several different resamplers - one that uses ACM (WaveFormatConversionStream), one that uses Media Foundation (MediaFoundationResampler) and one written entirely in managed code (WdlResamplingSampleProvider). I discuss each of these in this post.
For your case, you want to do "input driven" resampling, where you know how many input samples you have and just want to pass them into the resampler. This can be a bit trickier than output driven resampling in NAudio. I've written another post about how to do input driven resampling using AcmStream. A similar technique can be used with the Media Foundation resampler transform or the WDL Resampling Provider but I'm afraid I don't have a code sample of that available yet.

Getting MP4 File Duration with DirectShow

I need to get the duration of an mp4 file, preferably as a double in seconds. I was using DirectShow (see code below), but it keeps throwing a particularly unhelpful error. I'm wondering if someone has an easy solution to this. (Seriously, who knew that getting that information would be so difficult)
public static void getDuration(string moviePath)
{
FilgraphManager m_objFilterGraph = null;
m_objFilterGraph = new FilgraphManager();
m_objFilterGraph.RenderFile(moviePath);
IMediaPosition m_objMediaPosition = null;
m_objMediaPosition = m_objFilterGraph as IMediaPosition;
Console.WriteLine(m_objMediaPosition.Duration);
}
Whenever I run this code, I get the error: "Exception from HRESULT: 0x80040265"
I also tried using this: Getting length of video
but it doesn't work either because I don't think that it works on MP4 files.
Seriously, I feel like there has to be a much easier way to do this.
Note: I would prefer to avoid using exe's like ffmpeg and then parsing the output to get the information.

You are approaching the problem correctly. You need to build a good pipeline starting from source .MP4 file and up to video and audio renderers. Then IMediaPosition.Duration will get you what you want. Currently you are getting VFW_E_UNSUPPORTED_STREAM because you cannot build the pipeline.
Note that there is no good support for MPEG-4 in DirectShow in clean Windows, you need a third party parser installed to add missing blocks. This is the likely cause of your problem. There are good Free DirectShow Mpeg-4 Filters available to fill this gap.
The code sample under the link Getting length of video is basically valid too, however it uses deprecated component which in additional make additional assumptions onto the media file in question. Provided that there is support for .MP4 in the system, IMediaPosition.Duration is to give you what you look for.

You can use get_Duration() from IMediaPosition interface.
This return a double value with the video duration in seconds.
Double Lenght;
m_FilterGraph = new FilterGraph()
//Configure the FilterGraph()
m_mediaPosition = m_FilterGraph as IMediaPosition;
m_mediaPosition.get_Duration(out Length);

Using Windows Media Player Component also, we can get the duration of the video.
I hope that following code snippet may help you guys :
using WMPLib;
// ...
var player = new WindowsMediaPlayer();
var clip = player.newMedia(filePath);
Console.WriteLine(TimeSpan.FromSeconds(clip.duration));
and don't forget to add the reference of wmp.dll which will be
present in System32 folder.

How to capture screen to be video using C# .Net?

I know there are lots of question like this.
But I don't want to use the Windows media encoder 9 because it's a problem to get one, and then it is no longer supported.
I know that, one possibility is to capture lots of screenshots and create a video with ffmpeg but I don't want use third party executables.
Is there are a .net only solution?

the answer is the Microsoft Expression Encoder. It is according to my opinion the easiest way to record something on vista and windows 7
private void CaptureMoni()
{
try
{
Rectangle _screenRectangle = Screen.PrimaryScreen.Bounds;
_screenCaptureJob = new ScreenCaptureJob();
_screenCaptureJob.CaptureRectangle = _screenRectangle;
_screenCaptureJob.ShowFlashingBoundary = true;
_screenCaptureJob.ScreenCaptureVideoProfile.FrameRate = 20;
_screenCaptureJob.CaptureMouseCursor = true;
_screenCaptureJob.OutputScreenCaptureFileName = string.Format(#"C:\test.wmv");
if (File.Exists(_screenCaptureJob.OutputScreenCaptureFileName))
{
File.Delete(_screenCaptureJob.OutputScreenCaptureFileName);
}
_screenCaptureJob.Start();
}
catch(Exception e) { }
}

Edit Based on Comment Feedback:
A developer by the name baSSiLL has graciously shared a repository that has a screen recording c# library as well as a sample project in c# that shows how it can be used to capture the screen and mic.
Starting a screen capture using the sample code is as straight forward as:
recorder = new Recorder(_filePath,
KnownFourCCs.Codecs.X264, quality,
0, SupportedWaveFormat.WAVE_FORMAT_44S16, true, 160);
_filePath is the path of the file I'd like to save the video to.
You can pass in a variety of codecs including AVI, MotionJPEG, X264, etc. In the case of x264 I had to install the codec on my machine first but AVI works out of the box.
Quality only comes into play when using AVI or MotionJPEG. The x264 codec manages its own quality settings.
The 0 above is the audio device I'd like to use. The Default is zero.
It currently supports 2 wave formats. 44100 at 16bit either stereo or mono.
The true parameter indicates that I want the audio encoded into mp3 format. I believe this is required when choosing x264 as the uncompressed audio combined in a .mp4 file would not play back for me.
The 160 is the bitrate at which to encode the audio.
~~~~~
To stop the recording you just
recorder.Dispose();
recorder = null;
Everything is open source so you can edit the recorder class and change dimensions, frames per second, etc.
~~~~
To get up and running with this library you will need to either download or pull from the github / codeplex libraries below. You can also use NuGet:
Install-Package SharpAvi
Original Post:
Sharp AVI:
https://sharpavi.codeplex.com/
or
https://github.com/baSSiLL/SharpAvi
There is a sample project within that library that has a great screen recorder in it along with a menu for settings/etc.
I found Screna first from another answer on this StackoverFlow question but I ran into a couple issues involving getting Mp3 Lame encoder to work correctly. Screna is a wrapper for SharpAVI. I found by removing Screna and going off of SharpAvi's sample I had better luck.

c# DirectShow example shows black screen, but sound is OK

DirectShowLib.DVB-T example "DTVViewer" plays audio, but doesn't play video, I think it's because of H.264 video compressor, which is used in our Digital television and "DTVViewer" is trying to decompress MPEG2.
I want to ask how to form Graph and what filters to use to make "DTVViewer" support H.264?
CurrentGraph.
"MPEG2 DEMULTIPLEXER" pins:
(1)->BDA MPEG2 TRANSPORT INFORMATION FILTER
(2)->DScaler Mpeg2 Video Decoder->Video Renderer
(3)->AUDIO PART...
(5)->MPEG-2 SECTIONS AND TABLES
(ViPin) = AMMediaType(formatType?majorType?subType?)->Filter?->Video Renderer
Thinking, that now i only need help to configure new VideoPin correctly and add some H.264 decoder to it. Can anyone suggest something?
Thank you.

Try using Geraint Davies' free mpeg4 demux available at http://www.gdcl.co.uk/mpeg4/ instead of mpeg2 demultiplexer

If you are using Windows 7, you could look at using the Microsoft decoders. Take a look at the graph at this question: best way to build graph for MPEG2 transport stream.
As for what to specify for the video type, I use major type = video, subtype = H264, format type = video info.

Create Video out of image files?

I'm trying to make a video out of a folder full of jpeg files. I tried Google, and everybody is stuck with this. I have downloaded the WM SDK and the Encoder, but since the moment I don't know their object model I cant do much.
Does somebody here have some code WORKING about how to create a WMV or an AVI or a MPEG video file out of a folder full of jpegs? (In C#)
I can see on the answers that apparently there is no way to do it from C#, just using a third party. I will check your suggestions.

Take a look at Corinna John's AVIFile wrapper. I used it in the AVI output plugin for Cropper.

VirtualDub is capable of making a video out of several image files. Here's a quite overview of how to do it.
FFMPEG, as CptSkippy mentioned, also has this feature.

See the AVBlocks Slideshow sample. It creates a video (like MP4) from images. The input is a series of JPEG images. The output is configured with an AVBlocks preset.

Try via NuGet "accord.extensions.imaging.io", then I wrote the following little function:
private void makeAvi(string imageInputfolderName, string outVideoFileName, float fps = 12.0f, string imgSearchPattern = "*.png")
{ // reads all images in folder
VideoWriter w = new VideoWriter(outVideoFileName,
new Accord.Extensions.Size(480, 640), fps, true);
Accord.Extensions.Imaging.ImageDirectoryReader ir =
new ImageDirectoryReader(imageInputfolderName, imgSearchPattern);
while (ir.Position < ir.Length)
{
IImage i = ir.Read();
w.Write(i);
}
w.Close();
}
It reads all images from a folder and makes a video out of them.
If you want to make it nicer you could probably read the image dimensions instead of hard coding, but you got the point.

Have you considered using FFMPEG? I've used it to create thumbnails from video in several projects.

I finally settled on Splicer. Free, simple to use, and it works. More info at Working way to make video from images in C#