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• First HLS segment overlapping when renditions have different framerates

  7 septembre 2023, par drajvver

  I have a multi resolution m3u8 file, created from 1080p60 source file. Resolutions lower than 720p are converted to 30fps, while 720p+ stay at 60fps.

  


  The problem is that the first segment is broken between 30 and 60fps renditions, causing an overlap, which is detected by hls.js as a gap between segments for some reason.

  


  I have checked the segment files manually and it looks like they are fine, except for single audio frame missing between them, 60fps one has 187 'frames', while 30fps one has 186 'frames'.

  


  Videos are segmented in separate ffmpeg runs, but using the same settings, differing only in FPS, resolution and bitrate. Source file is always the same.

  


  Encoding parameters are : -async 30 -fps_mode cfr -vf "scale=640:-2,framerate=fps=30" -ac 2 -preset faster -crf 23 -b:a 128k -maxrate 1160k -bufsize 1600k -force_key_frames "expr:if(isnan(prev_forced_n),1,eq(n,prev_forced_n+30))" -g 30 -keyint_min 30 -sc_threshold 0 -hls_time 4 -hls_list_size 0 -hls_playlist_type vod -hls_flags independent_segments+discont_start -max_muxing_queue_size 9999 -profile:v main -pix_fmt yuv420p -fflags +genpts -r 30 - it's the same for 60fps, just with different resolution, bitrate and 30 gets replaced by 60

  


  Is there a way to fix this ?

  


  Thanks !

  


  


  


• mmaldec : limit internal buffering

  28 janvier 2016, par wm4

  mmaldec : limit internal buffering
  This uses a new MMAL feature, which limits the number of extra frames
  
  that can be buffered within the decoder. VIDEO_MAX_NUM_CALLBACKS can
  
  be defined as positive or negative number. Positive numbers are
  
  absolute, and can lead to deadlocks if the user underestimates the
  
  number of required buffers. Negative numbers specify the number of extra
  
  buffers, e.g. -1 means no extra buffer, (-1-N) means N extra buffers.
  Set a gratuitous default of -11 (N=10). This is much lower than the
  
  firmware default, which appears to be 96.
  This is backwards compatible, but needs a symbol only present in newer
  
  firmware headers. (It’s an enum item, so it requires a check in
  
  configure.)
  

  • [DH] configure
  • [DH] libavcodec/mmaldec.c

• even though my code is running without an error, it does not generate plot or video. I have xming runing

  23 octobre 2017, par Amin Abbasi

  This is my first code and I am really new to coding. I am trying to create a video or just plot my code.Eeven though my code is running without an error, I can’t get the video or the plot to generate. I have xming running and I have plotted a sample to make sure it not a computer Issue. I have also tried the following on GitHub but no success :
  https://jakevdp.github.io/blog/2013/05/19/a-javascript-viewer-for-matplotlib-animations/

  # -*- coding: utf-8 -*-
  
  import numpy as np
  
  def solver(I, V, f, c, L, dt, cc, T, user_action=None):
  
      """Solve u_tt=c^2*u_xx + f on (0,L)x(0,T]."""
  
      Nt = int(round(T/dt))
  
      t = np.linspace(0, Nt*dt, Nt+1) # Mesh points in time
  
      dx = dt*c/float(cc)
  
      Nx = int(round(L/dx))
  
      x = np.linspace(0, L, Nx+1) # Mesh points in space
  
      C2 = cc**2 # Help variable in the scheme
  
      # Make sure dx and dt are compatible with x and t
  
      dx = x[1] - x[0]
  
      dt = t[1] - t[0]
  
      if f is None or f == 0 :
  
          f = lambda x, t: 0
  
      if V is None or V == 0:
  
          V = lambda x: 0
  
      u       = np.zeros(Nx+1) # Solution array at new time level
  
      u_n     = np.zeros(Nx+1) # Solution at 1 time level back
  
      u_nm1   = np.zeros(Nx+1) # Solution at 2 time levels back
  
      import time; t0 = time.clock() # Measure CPU time
  
      # Load initial condition into u_n
  
      for i in range(0,Nx+1):
  
          u_n[i] = I(x[i])
  
      if user_action is not None:
  
          user_action(u_n, x, t, 0)
  
      # Special formula for first time step
  
      n = 0
  
      for i in range(1, Nx):
  
          u[i] = u_n[i] + dt*V(x[i]) + \
  
              0.5*C2*(u_n[i-1] - 2*u_n[i] + u_n[i+1]) + \
  
              0.5*dt**2*f(x[i], t[n])
  
      u[0] = 0; u[Nx] = 0
  
      if user_action is not None:
  
          user_action(u, x, t, 1)
  
      # Switch variables before next step
  
      u_nm1[:] = u_n; u_n[:] = u
  
      for n in range(1, Nt):
  
          # Update all inner points at time t[n+1]
  
          for i in range(1, Nx):
  
              u[i] = - u_nm1[i] + 2*u_n[i] + \
  
                      C2*(u_n[i-1] - 2*u_n[i] + u_n[i+1]) + \
  
                      dt**2*f(x[i], t[n])
  
          # Insert boundary conditions
  
          u[0] = 0; u[Nx] = 0
  
          if user_action is not None:
  
              if user_action(u, x, t, n+1):
  
                  break
  
          # Switch variables before next step
  
          u_nm1[:] = u_n; u_n[:] = u
  
      cpu_time = time.clock() - t0
  
      return u, x, t,
  
  def test_quadratic():
  
      """Check that u(x,t)=x(L-x)(1+t/2) is exactly reproduced."""
  
      def u_exact(x, t):
  
          return x*(L-x)*(1 + 0.5*t)
  
      def I(x):
  
          return u_exact(x, 0)
  
      def V(x):
  
          return 0.5*u_exact(x, 0)
  
      def f(x, t):
  
          return 2*(1 + 0.5*t)*c**2
  
      L = 2.5
  
      c = 1.5
  
      cc = 0.75
  
      Nx = 6 # Very coarse mesh for this exact test
  
      dt = cc*(L/Nx)/c
  
      T = 18
  
      def assert_no_error(u, x, t, n):
  
          u_e = u_exact(x, t[n])
  
          diff = np.abs(u - u_e).max()
  
          tol = 1E-13
  
          assert diff < tol
  
      solver(I, V, f, c, L, dt, cc, T,
  
              user_action=assert_no_error)
  
  def viz(
  
      I, V, f, c, L, dt, C, T,umin, umax, animate=True, tool='matplotlib'):
  
      """Run solver and visualize u at each time level."""
  
      def plot_u_st(u, x, t, n):
  
          """user_action function for solver."""
  
          plt.plot(x, u, 'r-')
  
  #                 xlabel='x', ylabel='u',
  
  #                 axis=[0, L, umin, umax],
  
  #                 title='t=%f' % t[n], show=True)
  
          # Let the initial condition stay on the screen for 2
  
          # seconds, else insert a pause of 0.2 s between each plot
  
          time.sleep(2) if t[n] == 0 else time.sleep(0.2)
  
          plt.savefig('frame_%04d.png' % n) # for movie making
  
      class PlotMatplotlib:
  
          def __call__(self, u, x, t, n):
  
              """user_action function for solver."""
  
              if n == 0:
  
                  plt.ion()
  
                  self.lines = plt.plot(x, u, 'r-')
  
                  plt.xlabel('x'); plt.ylabel('u')
  
                  plt.axis([0, L, umin, umax])
  
                  plt.legend(['t=%f' % t[n]], loc='lower left')
  
              else:
  
                  self.lines[0].set_ydata(u)
  
                  plt.legend(['t=%f' % t[n]], loc='lower left')
  
                  plt.draw()
  
              time.sleep(2) if t[n] == 0 else time.sleep(0.2)
  
              plt.savefig('tmp_%04d.png' % n) # for movie making
  
      if tool == 'matplotlib':
  
          import matplotlib.pyplot as plt
  
          plot_u = PlotMatplotlib()
  
      elif tool == 'scitools':
  
          import scitools.std as plt # scitools.easyviz interface
  
          plot_u = plot_u_st
  
      import time, glob, os
  
      # Clean up old movie frames
  
      for filename in glob.glob('tmp_*.png'):
  
          os.remove(filename)
  
      # Call solver and do the simulaton
  
      user_action = plot_u if animate else None
  
      u, x, t, cpu = solver_function(
  
          I, V, f, c, L, dt, C, T, user_action)
  
      # Make video files
  
      fps = 4 # frames per second
  
      codec2ext = dict(flv='flv', libx264='mp4', libvpx='webm',
  
                       libtheora='ogg') # video formats
  
      filespec = 'tmp_%04d.png'
  
      movie_program = 'ffmpeg' # or 'avconv'
  
      for codec in codec2ext:
  
          ext = codec2ext[codec]
  
          cmd = '%(movie_program)s -r %(fps)d -i %(filespec)s '\
  
                '-vcodec %(codec)s movie.%(ext)s' % vars()
  
          os.system(cmd)
  
      if tool == 'scitools':
  
          # Make an HTML play for showing the animation in a browser
  
          plt.movie('tmp_*.png', encoder='html', fps=fps,
  
                    output_file='movie.html')
  
      return cpu