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• Matplotlib : animation saved with trace

  25 mai 2020, par Thiziri yoor

  In the following Python code, I am trying to make an animation of a 2 rotating vectors around the origin. I am using matplotlib 3.2.1 and Python 3.8.2 on Ubuntu 20.04.

  



  
import numpy as np
import matplotlib.pyplot as plt

from matplotlib.animation import FuncAnimation


r = 2.0

def circle(phi):
    return np.array([r*np.cos(phi), r*np.sin(phi)])

fig, ax = plt.subplots(figsize=(10,6))
ax.axis([-3.5*r,3.5*r,-2.5*r,2.5*r])
ax.get_xaxis().set_visible(False)
ax.get_yaxis().set_visible(False)

# set equal aspect
ax.set_aspect("equal")

point, = ax.plot(0, r, marker="o")


traj = plt.Circle((0,0), r, fill=False, color='black')
ax.add_artist(traj) # draw the circular trajectory

def update(phi):

    x, y = circle(phi)
    point.set_data([x], [y])
    er_vec = np.array([0.5*x, 0.5*y])
    eθ_vec = np.array([-0.5*y, 0.5*x])


    er_arr = plt.arrow(x, y, dx=er_vec[0], dy=er_vec[1], head_width=0.1, head_length=0.2, color='gray')
    eθ_arr = plt.arrow(x, y, dx=eθ_vec[0], dy=eθ_vec[1], head_width=0.1, head_length=0.2, color='grey')

    annot_er = plt.text(1.7*x, 1.7*y, r'$\mathbf{e}_r$', fontsize=11)
    annot_eθ = plt.text(1.1*(x-0.5*y), 1.1*(y+0.5*x), r'$\mathbf{e}_\theta$', fontsize=11) 

    ax.add_artist(er_arr)    
    ax.add_artist(eθ_arr)
    ax.add_artist(annot_er)
    ax.add_artist(annot_eθ)
    return point, er_arr, eθ_arr, annot_er, annot_eθ

anim = FuncAnimation(fig, update, interval=10, blit=True, repeat=False, frames=np.linspace(0, 2.0*np.pi, 360, endpoint=False))
plt.show()


  



  The code above runs smoothly and without any issues.
This is a screenshot of the animation :

  



  

  



  However, when I try to save the animation to an mp4 video :

  



  anim.save('anim-issue.mp4', writer='ffmpeg')


  



  the animation in the video appears with traces which, something like this screenshot :

  



  

  



  Could someone help me fix that issue with the video animation ?

  



  I appreciate your help.

  



  Edit 1 : According to this answer this is due to blit=True. But that doesn't solve the issue here, since the arrows have no set_position method.

  



  Edit 2 : I found another related question with the same issue I described above but I don't know how to adapt my code to make it work as expected in both cases (plt.show, anim.save).

  


• Fragment shader does not show any colour when compiled with vs2013

  4 septembre 2019, par 5mayfive

  When compiled with vs2010, the fragment shader works, but when I compiled and run in vs 2013, it’s grey.

  My fragment shader converts the yuv texture into rgb

  Below is my fragment code

      const char *FProgram =
  
      "uniform sampler2D Ytex;\n"
  
      "uniform sampler2D Utex;\n"
  
      "uniform sampler2D Vtex;\n"
  
      "void main(void) {\n"
  
      "  vec4 c = vec4((texture2D(Ytex, gl_TexCoord[0]).r - 16./255.) * 1.164);\n"
  
      "  vec4 U = vec4(texture2D(Utex, gl_TexCoord[0]).r - 128./255.);\n"
  
      "  vec4 V = vec4(texture2D(Vtex, gl_TexCoord[0]).r - 128./255.);\n"
  
      "  c += V * vec4(1.596, -0.813, 0, 0);\n"
  
      "  c += U * vec4(0, -0.392, 2.017, 0);\n"
  
      "  c.a = 1.0;\n"
  
      "  gl_FragColor = c;\n"
  
      "}\n";
  
  
  
  
  
  
  
  
  
  
  
  glClearColor(0, 0, 0, 0);
  
  
  
  PHandle = glCreateProgram();
  
  FSHandle = glCreateShader(GL_FRAGMENT_SHADER);
  
  
  
  
  
  
  
  glShaderSource(FSHandle, 1, &FProgram, NULL);
  
  glCompileShader(FSHandle);
  
  
  
  glAttachShader(PHandle, FSHandle);
  
  glLinkProgram(PHandle);
  
  
  
  
  
  glUseProgram(PHandle);
  
  glDeleteProgram(PHandle);
  
  glDeleteProgram(FSHandle);

  This is my texture code, I receive linesize and yuv frame data from ffmpeg and make into texture. Everything works fine in VS 2010 computer, but when compiled and run in vs2013 computer, it is grey (black n white), no colour

      /* Select texture unit 1 as the active unit and bind the U texture. */
  
  glPixelStorei(GL_UNPACK_ROW_LENGTH, linesize1);
  
  glActiveTexture(GL_TEXTURE1);
  
  i = glGetUniformLocation(PHandle, "Utex");
  
  glUniform1i(i, 1);  /* Bind Utex to texture unit 1 */
  
  glBindTexture(GL_TEXTURE_2D, 1);
  
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
  glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, width / 2, height / 2, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, frame1);
  
  glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
  
  
  
  
  
  /* Select texture unit 2 as the active unit and bind the V texture. */
  
  glPixelStorei(GL_UNPACK_ROW_LENGTH, linesize2);
  
  glActiveTexture(GL_TEXTURE2);
  
  i = glGetUniformLocation(PHandle, "Vtex");
  
  glUniform1i(i, 2);  /* Bind Vtext to texture unit 2 */
  
  glBindTexture(GL_TEXTURE_2D, 2);
  
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
  glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, width / 2, height / 2, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, frame2);
  
  glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
  
  
  
  
  
  /* Select texture unit 0 as the active unit and bind the Y texture. */
  
  
  
  
  
  
  
  glPixelStorei(GL_UNPACK_ROW_LENGTH, linesize0);
  
  glActiveTexture(GL_TEXTURE0);
  
  i = glGetUniformLocation(PHandle, "Ytex");
  
  glUniform1i(i, 0);
  
  glBindTexture(GL_TEXTURE_2D, 0);
  
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
  glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, width, height, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, frame0);
  
  glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
  
  
  
  
  
  
  
  glClear(GL_COLOR_BUFFER_BIT);
  
  
  
  /* Draw image (again and again). */
  
  
  
  glBegin(GL_QUADS);
  
  glTexCoord2i(0, 0);
  
  glVertex2i(-w / 2, h / 2);
  
  glTexCoord2i(1, 0);
  
  glVertex2i(w / 2, h / 2);
  
  glTexCoord2i(1, 1);
  
  glVertex2i(w / 2, -h / 2);
  
  glTexCoord2i(0, 1);
  
  glVertex2i(-w / 2, -h / 2);
  
  glEnd();

• Decoding RIMM streaming file format

  1er août 2019, par ThomasRS

  I want to decode the video (visual) frames within a Blackberry RIMM file. So far I have a parser, and some corresponding container documentation from RIM. 

  The video codec is H264 and is explicitly set on the device using one of the video.encodings properties. However, FFMPEG is not able to decode the frames and this is driving me nuts.

  Edit 1 : The issues seems to be lack of SPS and PPS in the frames, and artificially inserting them have proven unsuccessful so far (all grey image). Blackberry 9700 sends

  0x00 0x00 0x ?? 0x ?? 0xType

  where Type is according to table 7-1 in the H264 spec (I and P frames). We believe the 0x ?? 0x ?? represent the size of the frame, however the size does not always correspond to the size found by the parser (the parser seems to be working correctly).

  I have a windows decoder codec from blackberry, called mc_demux_mp2_ds.ax, and can play some MPEG-4 files captured the same way, but it is a binary for windows. And the H264 files will not play either way. I am aware of previous attempts. The capture url for javax.microedition.media.Manager is

  encoding=video-3gpp_width=176_height=144_video_codec=H264_audio_codec=AAC

  and I am writing to an output stream. Some example files here.

  Edit 2 :Turns out that about 3-4 of the 12-15 available video capture modes are flat out failing and refusing to output data, even in the simplest of test applications. So any working solution should implement MPEG-4, H264 and H263 in both AMR and AAC, in so getting fallback alternatives when one sound codec and/or resolution fails. Reboots, hangs and what not litters the Blackberry video implementation and vary from firmware to firmware ; total suckage.