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• Decode H.264 stream from live555 using ffmpeg

  3 septembre 2013, par Straticiuc Vicu

  I try to decode H.264 frames for an IP Camera that uses onvif. For this i am using example testRTSPClient from live555. In FAQ is said that function afterGettingFrame() is called every time a new packet came in buffer and that packet is an NAL unit. On live555 part everything looks good. Now for decoding i am using ffmpeg and the frame i pass to the decoder are formed like discribed Here. Now my problem is that the ffmpeg is unable to decode my frames and i am getting errors like :

  top block unavailable for requested intra4x4 mode -1 at 18 0
  
  error while decoding MB 18 0
  
  no picture 
  
  P sub_mb_type 13 out of range at 2 3

  What am i doing wrong with ffmpeg ?

  PS. example of I-Frame passed to ffmpeg Here

   with:
  
   red   is startcode
  
   green is SPS info
  
   black is PPS info 
  
   blue  is I-Frame delivered by live555

• Detection of virtual background on video using ffmpeg

  28 juillet 2021, par Marcos G

  I am trying with ffmpeg to detect the use of a virtual background on a video, like the ones used in Google Meet. I got some ideas, but none seem to work :

  


  

  • Egde color : When using a chroma key you can get shades of green/blue on the outline of the subject. This is called spill, and can be detectable, but gets discarded by the fact that you dont need a chroma key to fake a background (example : Google Meet).

  


  • Still image : Most of virtual backgrounds are a still image pasted behind the subject. The problem with detecting this is that most of the real backgrounds also are like still images, without much movement.

  


  • Blur : When faking a background without a chroma key the outline of the subject becomes very blurry (this is more noticeable when the subject moves), but I can't find a way to detect it using ffmpeg.

  


  


  How can I do this ? I'm open to trying other tecniques such as AI.

  


  Thanks in advance.

  


• How to list all audio devices that are enabled and present for recording the output audio of the pc ?

  23 juin 2023, par Daniel Lip

  I want to record with ffmpeg later the entire desktop including audio.
I want to make that it will find for me automatic the recording audio device.

  


  I'm using MMDeviceEnumerator.

  


  all the other ways I tried returned empty list returned 0 audio devices. I tried with naudio and ffmpeg

  


  public Form1()
        {
            InitializeComponent();

            InitializeRecordingIndicator();

            MMDeviceEnumerator enumerator = new MMDeviceEnumerator();
            foreach (MMDevice device in enumerator.EnumerateAudioEndPoints(DataFlow.Capture, DeviceState.All))
            {
                StreamWriter w = new StreamWriter(@"d:\audiodev.txt", true);
                cmbAudioDevices.Items.Add(device.FriendlyName);
                w.WriteLine(device.FriendlyName + " " + device.State);
                w.Close();
            }
        }


  


  This is the list of all my audio deviceso n my system.
but they are all not present or disabled. and i have audio on my pc i can hear games videos anything.

  


  so what would i select from this list as audio device for recording the pc output audio ?
or maybe i need to find another way to find the right audio device ?

  


  Front Green In (Realtek(R) Audio) NotPresent
Rear (Realtek(R) Audio) NotPresent
Center (Realtek(R) Audio) NotPresent
Microphone (Realtek(R) Audio) NotPresent
Rear Grey In (Realtek(R) Audio) NotPresent
Side (Realtek(R) Audio) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Rear Pink In (Realtek(R) Audio) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Front (Realtek(R) Audio) NotPresent
Rear Orange In (Realtek(R) Audio) NotPresent
Line In (Realtek(R) Audio) NotPresent
Front Pink In (Realtek(R) Audio) NotPresent
Line In (Realtek(R) Audio) Unplugged
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Microphone (Realtek(R) Audio) Unplugged
Subwoofer (Realtek(R) Audio) NotPresent
Rear Black In (Realtek(R) Audio) NotPresent
Stereo Mix (Realtek(R) Audio) Disabled
Rear Green In (Realtek(R) Audio) NotPresent
Microphone (Realtek(R) Audio) NotPresent
Rear Blue In (Realtek(R) Audio) NotPresent
Front Green In (Realtek(R) Audio) NotPresent
Rear (Realtek(R) Audio) NotPresent
Center (Realtek(R) Audio) NotPresent
Microphone (Realtek(R) Audio) NotPresent
Rear Grey In (Realtek(R) Audio) NotPresent
Side (Realtek(R) Audio) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Rear Pink In (Realtek(R) Audio) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Front (Realtek(R) Audio) NotPresent
Rear Orange In (Realtek(R) Audio) NotPresent
Line In (Realtek(R) Audio) NotPresent
Front Pink In (Realtek(R) Audio) NotPresent
Line In (Realtek(R) Audio) Unplugged
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Microphone (Realtek(R) Audio) Unplugged
Subwoofer (Realtek(R) Audio) NotPresent
Rear Black In (Realtek(R) Audio) NotPresent
Stereo Mix (Realtek(R) Audio) Disabled
Rear Green In (Realtek(R) Audio) NotPresent
Microphone (Realtek(R) Audio) NotPresent
Rear Blue In (Realtek(R) Audio) NotPresent
Front Green In (Realtek(R) Audio) NotPresent
Rear (Realtek(R) Audio) NotPresent
Center (Realtek(R) Audio) NotPresent
Microphone (Realtek(R) Audio) NotPresent
Rear Grey In (Realtek(R) Audio) NotPresent
Side (Realtek(R) Audio) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Rear Pink In (Realtek(R) Audio) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (NVIDIA High Definition Audio) NotPresent
Front (Realtek(R) Audio) NotPresent
Rear Orange In (Realtek(R) Audio) NotPresent
Line In (Realtek(R) Audio) NotPresent
Front Pink In (Realtek(R) Audio) NotPresent
Line In (Realtek(R) Audio) Unplugged
Internal AUX Jack (High Definition Audio Device) NotPresent
Internal AUX Jack (High Definition Audio Device) NotPresent
Microphone (Realtek(R) Audio) Unplugged
Subwoofer (Realtek(R) Audio) NotPresent
Rear Black In (Realtek(R) Audio) NotPresent
Stereo Mix (Realtek(R) Audio) Disabled
Rear Green In (Realtek(R) Audio) NotPresent
Microphone (Realtek(R) Audio) NotPresent
Rear Blue In (Realtek(R) Audio) NotPresent


  


  this is how i tried with naudio but it didn't working it didn't find anything. :

  


  using NAudio.Wave;
...

// Enumerate and list audio input devices
var devices = WaveInEvent.DeviceCount;
for (int deviceId = 0; deviceId < devices; deviceId++)
{
    var deviceInfo = WaveInEvent.GetCapabilities(deviceId);
    Console.WriteLine($"Device ID: {deviceId}, Name: {deviceInfo.ProductName}");
}


  


  before that i tried with ffmpeg but also it didn't return anything :

  


  public static class FFmpegHelper
    {
        public static string[] GetAudioCaptureDevices()
        {
            string ffmpegPath = @"C:\path\to\ffmpeg.exe";
            Process process = new Process();
            process.StartInfo.FileName = ffmpegPath;
            process.StartInfo.Arguments = "-list_devices true -f dshow -i dummy";
            process.StartInfo.UseShellExecute = false;
            process.StartInfo.RedirectStandardError = true;
            process.StartInfo.CreateNoWindow = true;
            process.Start();
            process.WaitForExit();

            string output = process.StandardError.ReadToEnd();
            string[] lines = output.Split('\n');
            var devices = lines.Where(line => line.Contains("audio")).Select(line => line.Trim()).ToArray();
            return devices;
        }
    }


  


  using it :

  


  var audioDevices = FFmpegHelper.GetAudioCaptureDevices();