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• Matplotlib use Ffmpeg to save plot to be mp4 not include full step

  21 décembre 2020, par 昌翰余

  I use ffmpeg to store the dynamic graph drawn on matplotlib, but the output file is only 2 seconds
but It should have been 30 seconds.
I set a graph to run three curves, a total of 30 seconds of data,
the graph that ran on the py file is normal,
but the output is only the first two seconds of the output.
May I ask if I missed something

  


  Below is my code

  


  import matplotlib.pyplot as plt
from matplotlib import animation
from numpy import random 
import pandas as pd
from matplotlib.animation import FFMpegWriter

FFwriter=animation.FFMpegWriter(fps=30, extra_args=['-vcodec', 'libx264'])
data = pd.read_csv('apple1.csv', delimiter = ',', dtype = None)
data = data.values
AccX1=[]
AccY1=[]
AccZ1=[]
AccX2=[]
AccY2=[]
AccZ2=[]

time = []

for i in range(600):
        AccX1.append(data[i][8])
        AccY1.append(data[i][9])
        AccZ1.append(data[i][10])
        AccX2.append(data[i][24])
        AccY2.append(data[i][25])
        AccZ2.append(data[i][26])
        
        time.append(data[i][0])
        
fig = plt.figure()
ax1 = plt.axes(xlim=(0,3000), ylim=(6,-6))
line, = ax1.plot([], [], lw=2)
plt.xlabel('ACC')
plt.ylabel('Time')

plotlays, plotcols = [3], ["r","g","b"]
lines = []
for index in range(3):
    lobj = ax1.plot([],[],lw=2,color=plotcols[index])[0]
    lines.append(lobj)


def init():
    for line in lines:
        line.set_data([],[])
    return lines

x1,y1 = [],[]
x2,y2 = [],[]
x3,y3 = [],[]



i=0

def animate(frame):
    global i
    
    i+=1
    x = i
    y = AccX1[i]

    x1.append(x)
    y1.append(y)

    x = i
    y = AccY1[i]
    x2.append(x)
    y2.append(y)

    x = i
    y = AccZ1[i]
    x3.append(x)
    y3.append(y)
    

    xlist = [x1, x2,x3]
    ylist = [y1, y2,y3]


    for lnum,line in enumerate(lines):
        line.set_data(xlist[lnum], ylist[lnum]) 


    return lines


anim = animation.FuncAnimation(fig, animate,
                    init_func=init, blit=True,interval=10)
anim.save('test.mp4',writer=FFwriter)
plt.show()


  


  The dynamic picture ran out using plt.show is correct.
And I don't think I have set the length of storage. Did I add something ?

  


• FFMPEG unable to take frame and save as image

  2 mai 2013, par alex

  I'm trying to save an image from a video frame and save it as a jpeg.
  This function works for smaller video files, but if the video is over 10 minutes it won't save the jpeg image. An error comes up as before trans.

  public function VideoToJpeg($localVideoPath, $localOutImgPath)
  
  {
  
      $Name = dirname(__FILE__) . "/ffmpeg";
  
      $Str = "$Name -i \"$localVideoPath\" -an -ss 00:00:03 -an -r 1 -vframes 1 -y \"$localOutImgPath\"";
  
  
  
      exec($Str);
  
  }

  Here is the error I got from ffmpeg

  [NULL @ 0370e760] Unable to find a suitable output format for 'path'
  
  : Invalid argument

• SDL save screenshot on iOS

  12 avril 2018, par Law Gimenez

  I am trying to save a screen or frame from the SDL’s "window" into a PNG file and so I’m using SDL_image library. My code is below

  IMG_Init(Int32(IMG_INIT_PNG.rawValue))
  
  let screenShot = SDL_CreateRGBSurface(0, 640, 480, 32, 0, 0, 0, 0)
  
  SDL_SetRenderTarget(renderer, texture)
  
  SDL_RenderReadPixels(renderer, nil, Uint32(SDL_PIXELFORMAT_ARGB8888), screenShot?.pointee.pixels, (screenShot?.pointee.pitch)!)
  
  let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
  
  IMG_SavePNG(screenShot, "\(documentsPath)/image.png")
  
  SDL_FreeSurface(screenShot)

  But the image.png was not saved. If anyone can lead or help me. Thank you !

  Additional code, the image saved is just black

  IMG_Init(Int32(IMG_INIT_PNG.rawValue))
  
  let screenShot = SDL_CreateRGBSurface(Uint32(SDL_SWSURFACE), 640, 480, 32, 0, 0, 0, 0)
  
  // SDL_SetRenderTarget(renderer, texture)
  
  SDL_RenderReadPixels(renderer, nil, Uint32(SDL_PIXELFORMAT_ARGB8888), screenShot?.pointee.pixels, (screenShot?.pointee.pitch)!)
  
  // Save to documents directory
  
  let fileManager = FileManager.default
  
  do {
  
      let documentDirectory = try fileManager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
  
      let fileUrl = documentDirectory.appendingPathComponent("imageLOL.png")
  
      if !fileManager.fileExists(atPath: fileUrl.path) {
  
          print("File NO exists")
  
          // Create file at path
  
          let data = Data()
  
          let createFile = fileManager.createFile(atPath: fileUrl.path, contents: data, attributes: nil)
  
          if createFile {
  
              print("Create file success")
  
          } else {
  
              print("Create file failed")
  
          }
  
      } else {
  
          print("File exists")
  
  
  
      }
  
      let result = IMG_SavePNG(screenShot, fileUrl.path)
  
      print("result = \(result)")
  
      // After saving screenshot
  
      let image = UIImage(contentsOfFile: fileUrl.path)
  
      let imageData = UIImagePNGRepresentation(image!)
  
      print("image length = \(String(describing: imageData?.count))")
  
      UIImageWriteToSavedPhotosAlbum(image!, nil, nil, nil)
  
      SDL_FreeSurface(screenShot)
  
  } catch {
  
      print("Error docs = \(error)")
  
  }