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• Why multithead use more cpu than single for the same task of deocoing H.264 video ?

  29 juillet 2018, par gary

  I am developing an PC hardware accelerated video decoder for decoding real time H264 Annex B stream. After a bit research, I have done this job by ffmpeg. However, I try to decople the decoding process and show process, the cpu bumped.

  What I want to do is to acceleratly decode a living H.264 stream to yuv, and convert YUV to BGR for cv::Mat without display.

  I can acceleratly decode the h.264 by ffmpeg with decoder h264_qsv, the cpu usage decrease 15% indeed. Then I try to do another thing that put then CV::Mat to std::queue and read the Mat from another queue which just read with do anything else. But the cpu bumped to 30%.

  At first, I think the std::mutex accessed frequently made the performance worse, I try to use a bool flag as lock, but it seems does not work.

  How can I approach ? I have no idear why mulithread make the cpu usage increase. Is there any helpful resources to get clear intuition ?

  frame enqueue

     av_frame_q_lock.lock();
  
     if (av_frame_q.size() == MAX_QUEUE_SIZE) {
  
          av_frame_q.pop();
  
      }
  
      av_frame_q.push(cvframe);
  
      av_frame_q_lock.unlock();

  frame dequeue

      hwrtsp_open("rtsp://admin:123@10.20.37.185/cam/realmonitor?channel=1&subtype=0", "h264_qsv");
  
  cv::Mat frame;
  
  while (true) {
  
      int ret = hwrtsp_read(frame);
  
      if (ret == 0) {
  
      }
  
      cv::waitKey(40);
  
  }

  Thanks in advance !

• Crontab task scheduled every hour stops running from 11am to 12am

  11 août 2019, par technik

  I have a rather weird issue. My aim is to use ffmpeg to grab a screenshot from a home CCTV cameras rtsp stream every hour. I want to do this in order to make a timelapse. However everyday from 11am to 12am (the next day) there are no snapshots saved.

  On an always on Debian machine, this is the shell script I have that crontab calls :

  dt=$(date +"%d%m%2y%I%M%S")
  
  ffmpeg -rtsp_transport tcp -i "rtsp://IP:554/..." -frames 1 /user/snapshots/ch1/$dt.jpg

  Running it by itself works fine and saves a jpg snapshot successfully to the right folders.

  In crontab -e I have the following line :
  0 * * * * /bin/sh //user/snap.sh

  Thanks.

• Using ffmpeg.exe making the computer slow in task manager it takes over 1GB of memory how can i fix it ?

  29 mai 2013, par Revuen Ben Dror

  In mt Form1 i have this code :

  private void StartRecording_Click(object sender, EventArgs e)
  
          {
  
  
  
              ffmp.Start("test.avi", 25);
  
              timer1.Enabled = true;
  
          }

  ffmp is a variable of my class : Ffmpeg
  In this class i add frames to a pipe and create an avi file.

  using System;
  
  using System.Collections.Generic;
  
  using System.Linq;
  
  using System.Text;
  
  using System.Threading.Tasks;
  
  using System.Drawing;
  
  using System.IO.Pipes;
  
  using System.Runtime.InteropServices;
  
  using System.Diagnostics;
  
  
  
  namespace ScreenVideoRecorder
  
  {
  
      class Ffmpeg
  
      {
  
          NamedPipeServerStream p;
  
          String pipename = "mytestpipe";
  
          byte[] b;
  
          System.Diagnostics.Process process;
  
  
  
          public Ffmpeg()
  
          {
  
  
  
          }
  
  
  
          public void Start(string FileName, int BitmapRate)
  
          {
  
              p = new NamedPipeServerStream(pipename, PipeDirection.Out, 1, PipeTransmissionMode.Byte);
  
              b = new byte[1920 * 1080 * 3]; // some buffer for the r g and b of pixels of an image of size 720p 
  
              process = new System.Diagnostics.Process();
  
              process.StartInfo.FileName = @"D:\pipetest\pipetest\ffmpegx86\ffmpeg.exe";
  
              process.EnableRaisingEvents = false;
  
              process.StartInfo.WorkingDirectory = @"D:\pipetest\pipetest\ffmpegx86";
  
              process.StartInfo.Arguments = @"-f rawvideo -pix_fmt bgr0 -video_size 1920x1080 -i \\.\pipe\mytestpipe -map 0 -c:v libx264 -r " + BitmapRate + " " + FileName;
  
              process.Start();
  
  
  
              process.StartInfo.UseShellExecute = false;
  
              process.StartInfo.CreateNoWindow = false;
  
  
  
              p.WaitForConnection();
  
          }
  
  
  
          public void PushFrame(Bitmap bmp)
  
          {
  
  
  
              int length;
  
              // Lock the bitmap's bits.
  
              Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
  
              //Rectangle rect = new Rectangle(0, 0, 1280, 720);
  
              System.Drawing.Imaging.BitmapData bmpData =
  
                  bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadOnly,
  
                  bmp.PixelFormat);
  
  
  
              int absStride = Math.Abs(bmpData.Stride);
  
              // Get the address of the first line.
  
              IntPtr ptr = bmpData.Scan0;
  
  
  
              // Declare an array to hold the bytes of the bitmap.
  
              //length = 3 * bmp.Width * bmp.Height;
  
              length = absStride * bmpData.Height;
  
              byte[] rgbValues = new byte[length];
  
  
  
              int j = bmp.Height - 1;
  
              for (int i = 0; i < bmp.Height; i++)
  
              {
  
                  IntPtr pointer = new IntPtr(bmpData.Scan0.ToInt32() + (bmpData.Stride * j));
  
                  System.Runtime.InteropServices.Marshal.Copy(pointer, rgbValues, absStride * (bmp.Height - i - 1), absStride);
  
                  j--;
  
              }
  
  
  
              p.Write(rgbValues, 0, length);
  
  
  
              bmp.UnlockBits(bmpData);
  
  
  
          public void Close()
  
          {
  
              p.Close();
  
          }
  
      }
  
  }

  The problem is when i'm running my application in this from my visual studio 2012 pro and click the button it's openning a console window and start the processing .

  I tracked over it through the task manager on ffmpeg.exe and saw that it started from 996mb and very quick jumped ot 1040mb memory usage. The cpu usage was only 16%

  Once i close ended this task the ffmpeg.exe everything was back to move smooth.
  When it's working and i tried to drag my Form around the screen for example it was moving slow and also with some stuttering .

  Closed the ffmpeg.exe and i could drag the Form around smooth and quick like in regular way as it should be.

  I tried to google for it and found some others with the same problem i think but i'm not sure where is the problem and how to fix it.

  I'm not sure what version of ffmpeg.exe i have i'm using now but i read in some places that it's not working better with new versions but maybe i mistake here .

  My windows is 8 with 6gb of ram .