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• cutting video using ffmpeg cannot produce videos with specified length

  22 juin 2021, par david

  I have some mp4 videos and I want to split them into 2-second videos. my GOP is 2 Sec. for this aim I use the following command :

  


  ffmpeg -i input.mp4 -c copy -map 0 -segment_time 00:00:02 -f segment -reset_timestamps 1 output%03d.mp4


  


  but after splitting, my new videos have different duration times. some of them are 4 Sec, one of them is 3.67 Sec. why the duration time is different from the thing I specified in command ? my command is wrong ?
is it possible to split based on frame number ? for example each 120 frame ?

  


• Livestreaming screencast to Youtube through ffmpeg doesn't show video even though data is received [duplicate]

  15 novembre 2017, par CindyRabbit

  This question already has an answer here :

  • YouTube live says not receiving data
    
    1 answer
    
  • adding silent audio in ffmpeg
    
    4 answers
    

  I am trying to livestream my Desktop in Ubuntu to Youtube and used this cmd. Youtube livestream showed green bar with "Receiving your data" and Youtube log also showed "Stream healthy", however no video showed up in Youtube player, and after a short while Youtube log said "Stream complete". What’s missing in my cmd ?

  ffmpeg -f x11grab -r 10 -s 1024x720 -i :0.0 -vcodec libx264 -pix_fmt yuv420p -preset ultrafast -g 20 -b:v 2500k -threads 0 -bufsize 512k -f flv rtmp ://a.rtmp.youtube.com/live2/myKey

  BTW, only screencasting doesn’t work for me, streaming a video file works for me.

• 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();