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• avfilter/all : propagate errors of functions from avfilter/formats

  5 octobre 2015, par Ganesh Ajjanagadde

  avfilter/all : propagate errors of functions from avfilter/formats
  Many of the functions from avfilter/formats can return errors, usually AVERROR(ENOMEM).
  
  This propagates the return values.
  All of these were found by using av_warn_unused_result, demonstrating its utility.
  Tested with FATE. I am least sure of the changes to avfilter/filtergraph,
  
  since I don’t know what/how reduce_format is intended to behave and how it should
  
  react to errors.
  Fixes : CID 1325680, 1325679, 1325678.
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Previous version Reviewed-by : Nicolas George <george@nsup.org>
  
  Previous version Reviewed-by : Clément Bœsch <u@pkh.me>
  
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  

  • [DH] libavfilter/aeval.c
  • [DH] libavfilter/af_aformat.c
  • [DH] libavfilter/af_agate.c
  • [DH] libavfilter/af_amerge.c
  • [DH] libavfilter/af_amix.c
  • [DH] libavfilter/af_aresample.c
  • [DH] libavfilter/af_astreamsync.c
  • [DH] libavfilter/af_channelmap.c
  • [DH] libavfilter/af_channelsplit.c
  • [DH] libavfilter/af_earwax.c
  • [DH] libavfilter/af_extrastereo.c
  • [DH] libavfilter/af_join.c
  • [DH] libavfilter/af_pan.c
  • [DH] libavfilter/af_replaygain.c
  • [DH] libavfilter/af_resample.c
  • [DH] libavfilter/af_sidechaincompress.c
  • [DH] libavfilter/af_stereotools.c
  • [DH] libavfilter/af_stereowiden.c
  • [DH] libavfilter/asrc_anullsrc.c
  • [DH] libavfilter/asrc_flite.c
  • [DH] libavfilter/avf_aphasemeter.c
  • [DH] libavfilter/avf_avectorscope.c
  • [DH] libavfilter/avf_concat.c
  • [DH] libavfilter/avf_showcqt.c
  • [DH] libavfilter/avf_showfreqs.c
  • [DH] libavfilter/avf_showspectrum.c
  • [DH] libavfilter/avf_showvolume.c
  • [DH] libavfilter/avf_showwaves.c
  • [DH] libavfilter/avfiltergraph.c
  • [DH] libavfilter/buffersink.c
  • [DH] libavfilter/buffersrc.c
  • [DH] libavfilter/drawutils.c
  • [DH] libavfilter/f_drawgraph.c
  • [DH] libavfilter/f_ebur128.c
  • [DH] libavfilter/formats.c
  • [DH] libavfilter/src_movie.c
  • [DH] libavfilter/vf_alphamerge.c
  • [DH] libavfilter/vf_boxblur.c
  • [DH] libavfilter/vf_crop.c
  • [DH] libavfilter/vf_detelecine.c
  • [DH] libavfilter/vf_displace.c
  • [DH] libavfilter/vf_elbg.c
  • [DH] libavfilter/vf_extractplanes.c
  • [DH] libavfilter/vf_fieldorder.c
  • [DH] libavfilter/vf_frei0r.c
  • [DH] libavfilter/vf_hflip.c
  • [DH] libavfilter/vf_histogram.c
  • [DH] libavfilter/vf_il.c
  • [DH] libavfilter/vf_maskedmerge.c
  • [DH] libavfilter/vf_mergeplanes.c
  • [DH] libavfilter/vf_neighbor.c
  • [DH] libavfilter/vf_noise.c
  • [DH] libavfilter/vf_overlay.c
  • [DH] libavfilter/vf_palettegen.c
  • [DH] libavfilter/vf_paletteuse.c
  • [DH] libavfilter/vf_scale.c
  • [DH] libavfilter/vf_showpalette.c
  • [DH] libavfilter/vf_stack.c
  • [DH] libavfilter/vf_swapuv.c
  • [DH] libavfilter/vf_telecine.c
  • [DH] libavfilter/vf_transpose.c
  • [DH] libavfilter/vf_vectorscope.c
  • [DH] libavfilter/vsrc_life.c

• attempting to save FuncAnimation changes the animation

  25 mars 2024, par pibion

  I am attempting to create and save an animation of a time-varying vector field using matplotlib's FuncAnimation. When I run the animation without attempting to save it, it updates smoothly as expected. However, when I try to save the animation, the vectors increase in length and the animation only appears to update a few times. I've been able to record the screen to get a video file, but I'd like to understand how to save the animation to a video in python.

  


  Here is the code to create the vector field animation. I ran this in a local jupyter notebook using python 3.9.12 on Windows.

  


  %matplotlib notebook
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation

x_min, x_max = -20, 20
y_min, y_max = 0, 25
wire_x = -4
wire_y = 17

# Define the vector field function (example: rotating vector field)
def vector_field(x, y, t):
    x = x - wire_x
    y = y - wire_y
    r = np.sin(t) / (x**2 + y**2)
    u = -r * y
    v = r * x
    return (u, v)

# Define grid
x = np.linspace(x_min, x_max, 20)
y = np.linspace(y_min, y_max, 20)
X, Y = np.meshgrid(x, y)

# Create animation
fig, ax = plt.subplots(1,1)
ax.set_aspect('equal')
ax.set_xlim(x_min, x_max)
ax.set_ylim(y_min, y_max)
ax.set_xlabel('X (m)')
ax.set_ylabel('Y (m)')

u, v = vector_field(X, Y, 1)

quiver = ax.quiver(X, Y, u, v)

time_arr = np.linspace(0,20,200)

plt.show()

def update_quiver(num):
    t = num * 0.1  # Time step
    u, v = vector_field(X, Y, t)
    quiver.set_UVC(u, v)

ani = animation.FuncAnimation(fig, update_quiver, frames=200, interval=50, repeat=False)


  


  This produces an animation whose vectors smoothly vary in length on my computer.

  


  However, when I try to save the animation by adding the lines

  


  writervideo = animation.FFMpegWriter(fps=60) 
ani.save('field_leftWire.mp4', writer=writervideo) 


  


  then the animation changes - the vectors are much longer and it appears to only update a few times throughout the animation.

  


  I'll also note that I had to install ffmpeg and restart my computer as outlined in Installation of FFMPEG for Python in WIndows to get the last two lines to run without error.

  


• FFmpeg zoompan animation results in zig-zag pattern [closed]

  2 février 2024, par kregus

  please assist, as I am pulling my hair out !

  


  The goal is for a user to specify a zoomPoint in a video as follows :

  


  {
   "scale":4,        # Scale factor, here x4
   "offset":0,       # Start zooming in after 0ms
   "duration":5000,  # Stay zoomed in for 5000ms
   "marginX":80,     # Zoom x to 80% of video width 
   "marginY":10      # Zoom y to 10% of video height
}


  


  I am running the following, simplified FFmpeg command :

  


  ffmpeg -i "/tmp/input.mp4" -c:v libx264 -r 30 -vf "scale=iw*2:ih*2,zoompan=fps=30:z='if(gte(it,0.0)*lt(it,5.0), min(pzoom+0.2, 4),if(gte(it,5.0)*lt(it,5.5), max(pzoom-0.2, 1), 1))':d=1:s=1512x982:x='(iw - iw/4)*(80/100)':y='(ih - ih/4)*(10/100)'" /tmp/output.mp4


  


  The animation duration is 0.5s, the video framerate is 30fps, and so there are 0.5 / (1/30) = 15 animation frames.

  


  Zoom distance is scale - 1 = 3 in this case, which makes the zoom increment 3 / 15 = 0.2.

  


  This results in the following example video : click here

  


  While the zoom animation ends in the correct position, you will notice it arrives at that position in a zig-zag pattern, where it starts by zooming into the top-right corner, before changing direction towards the correct position.

  


  I cannot seem to figure out how to get it to animate the zoom in a straight line to the specified x/y position.

  


  Any tips are welcome, thanks !