Recherche avancée

Sur d’autres sites (6324)

• ffmpeg, download video stream from url

  1er décembre 2014, par samiullah

  I am developing application to save any online webinar(video or audio) given the url using ffmpeg library. Url usually contain other contents like text, images as well. So i have problem, how to separately get video stream from url using ffmpeg(or some other better free library). Url may be for any site, not only for youtube, but as an example, link may be like
  http://wildkingdom.magnify.net/video/Dangerous-Moments-in-the-Wild-K ;recent or
  http://www.youtube.com/watch?v=wnrJJYm7qIw
  etc

• Cannot save animation in matplotlib : Windows permission denied

  13 mai 2015, par Vladimir

  I’ve been trying for a day long to sort this out, checking similar threads but with no success.
  Stretch’s Cannot save matplotlib animation with ffmpeg helped with previous errors (I had ffmpeg path wrong), but I kept getting Access denied after fixing it.

  My ffmpeg binary is on C:\ffmpeg\bin

  A nice alternative would be to able to export gif files, but I keep getting an ascii error with imagemagick. I think both problems are related, so I wanted to sort out the ffmpeg first.

  I think the problem might have to do with the fact I’m working with Canopy (in Windows 8 64bit), which pretty much hegemonized my path variable and broke some things along the way (e.g. I can’t open IDLE since I installed Canopy, didn’t tried to fix that yet). As I fixed things along the way I found at least 3 distinct path variables, all of which I updated : windows advanced settings path (set manually), windows console path (set via console with setx), and sys.path (set or checked at runtime), adding ";C:\ffmpeg\bin", where ffmpeg effectively is. Regardless I sort out the problem or not, I would like to learn which of these environment variables are relevant for what, I find it very confusing.

  The code is the following :

  # -*- coding: utf-8 -*-
  
  import sys
  
  import numpy as np
  
  from matplotlib import pyplot as plt
  
  from matplotlib import animation
  
  plt.rcParams['animation.ffmpeg_path'] = r'C:\ffmpeg\bin'
  
  if r'C:\ffmpeg\bin' not in sys.path: sys.path.append(r'C:\ffmpeg\bin')
  
  
  
  fig = plt.figure()
  
  ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
  
  line, = ax.plot([], [], lw=2)
  
  
  
  def init():
  
      line.set_data([], [])
  
      return line,
  
  
  
  def animate(i):
  
      x = np.linspace(0, 2, 1000)
  
      y = np.sin(2 * np.pi * (x - 0.01 * i))
  
      line.set_data(x, y)
  
      return line,
  
  
  
  anim = animation.FuncAnimation(fig, animate, init_func=init, frames=200, interval=20, blit=True)
  
  plt.show()
  
  
  
  # This case generates Windows err: Access Denied
  
  FFwriter = animation.FFMpegWriter()
  
  # anim.save(r'C:\basic_animation.mp4', writer = FFwriter, fps=30)
  
  
  
  # This case generates UnicodeDecodeError:'ascii' codec can't decode byte 0xa0 in position 3
  
  # anim.save(r'C:\animation.gif', writer='imagemagick', fps=30)

  The traceback for anim.save(r'C:\basic_animation.mp4', writer = FFwriter, fps=30) :

  %run "C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py"
  
  ---------------------------------------------------------------------------
  
  WindowsError                              Traceback (most recent call last)
  
  C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py in <module>()
  
       27 # This case generates Windows err: Access Denied
  
       28 FFwriter = animation.FFMpegWriter()
  
  ---> 29 anim.save(r'C:\basic_animation.mp4', writer = FFwriter, fps=30)
  
       30 
  
       31 # This case generates UnicodeDecodeError:'ascii' codec can't decode byte 0xa0 in position 3
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in save(self, filename, writer, fps, dpi, codec, bitrate, extra_args, metadata, extra_anim, savefig_kwargs)
  
      759         # since GUI widgets are gone. Either need to remove extra code to
  
      760         # allow for this non-existant use case or find a way to make it work.
  
  --> 761         with writer.saving(self._fig, filename, dpi):
  
      762             for data in zip(*[a.new_saved_frame_seq()
  
      763                               for a in all_anim]):
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\App\appdata\canopy-1.5.2.2785.win-x86_64\lib\contextlib.pyc in __enter__(self)
  
       15     def __enter__(self):
  
       16         try:
  
  ---> 17             return self.gen.next()
  
       18         except StopIteration:
  
       19             raise RuntimeError("generator didn't yield")
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in saving(self, *args)
  
      184         '''
  
      185         # This particular sequence is what contextlib.contextmanager wants
  
  --> 186         self.setup(*args)
  
      187         yield
  
      188         self.finish()
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in setup(self, fig, outfile, dpi, *args)
  
      174         # Run here so that grab_frame() can write the data to a pipe. This
  
      175         # eliminates the need for temp files.
  
  --> 176         self._run()
  
      177 
  
      178     @contextlib.contextmanager
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in _run(self)
  
      202                                       stdout=output, stderr=output,
  
      203                                       stdin=subprocess.PIPE,
  
  --> 204                                       creationflags=subprocess_creation_flags)
  
      205 
  
      206     def finish(self):
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\App\appdata\canopy-1.5.2.2785.win-x86_64\lib\subprocess.pyc in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags)
  
      707                                 p2cread, p2cwrite,
  
      708                                 c2pread, c2pwrite,
  
  --> 709                                 errread, errwrite)
  
      710         except Exception:
  
      711             # Preserve original exception in case os.close raises.
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\App\appdata\canopy-1.5.2.2785.win-x86_64\lib\subprocess.pyc in _execute_child(self, args, executable, preexec_fn, close_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, to_close, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite)
  
      955                                          env,
  
      956                                          cwd,
  
  --> 957                                          startupinfo)
  
      958             except pywintypes.error, e:
  
      959                 # Translate pywintypes.error to WindowsError, which is
  
  
  
  WindowsError: [Error 5] Acceso denegado 
  
  </module>

  The traceback for anim.save(r'C:\animation.gif', writer='imagemagick', fps=30) :

  In [8]: %run "C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py"
  
  ---------------------------------------------------------------------------
  
  UnicodeDecodeError                        Traceback (most recent call last)
  
  C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py in <module>()
  
       30 
  
       31 # This case generates UnicodeDecodeError:'ascii' codec can't decode byte 0xa0 in position 3
  
  ---> 32 anim.save(r'C:\animation.gif', writer='imagemagick', fps=30)
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in save(self, filename, writer, fps, dpi, codec, bitrate, extra_args, metadata, extra_anim, savefig_kwargs)
  
      765                     # TODO: Need to see if turning off blit is really necessary
  
      766                     anim._draw_next_frame(d, blit=False)
  
  --> 767                 writer.grab_frame(**savefig_kwargs)
  
      768 
  
      769         # Reconnect signal for first draw if necessary
  
  
  
  C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in grab_frame(self, **savefig_kwargs)
  
      225             verbose.report('MovieWriter -- Error '
  
      226                            'running proc:\n%s\n%s' % (out,
  
  --> 227                                                       err), level='helpful')
  
      228             raise
  
      229 
  
  
  
  UnicodeDecodeError: 'ascii' codec can't decode byte 0xa0 in position 3: ordinal not in range(128) 
  
  </module>

  Stared at them for a while.

  Thanks for your time !

  UPDATE : I followed the steps in this post for granting access to both C :\ffmpeg and destination folder, but no luck :(

• SDL2 won't play with more than 6 audio channels

  13 juin 2020, par Hiko Haieto

  I am trying to stream (raw) video and audio from a capture device as part of my home media setup (with my pc acting similarly to a receiver in a typical home theatre setup), but the biggest problem I haven't been able to get past is that I haven't been able to get ffplay (using SDL2 as its audio backend) to work with all 8 channels in 7.1 streams - two simply get dropped, despite it recognising 8 channel input or me specifying a 7.1 layout.

  



  I have been able to confirm that all 8 channels are present in the source by first using ffmpeg to save the output of a speaker test to a file and playing that back with both mplayer (which works) and ffplay (which doesn't). I also wrote some minimal code to play the audio directly through SDL's API with the same result, so it's not the fault of ffplay. I might simply use mplayer if it weren't for the fact that piping output from ffmpeg adds too much latency for real-time use. I am using libSDL version 2.0.12 and ffplay 4.2.3, both of which are the latest at the time of writing and are ostensibly supposed to support 7.1 audio.

  



  Using output recorded from speaker-test -c 8, I am using the following to play it back in mplayer :

  



  mplayer -channels 8 -rawaudio channels=8 -format s16le -demuxer rawaudio speaker-test.pcm


  



  and the following to play it back in ffplay :

  



  ffplay -f s16le -ac 8 -af 'channelmap=channel_layout=7.1' speaker-test.pcm


  



  No matter what I try, the two side channels get dropped. I couldn't figure out how to play raw pcm in SDL, so I repeated the same tests with wav output and used the following code to play it back :

  



  #include <sdl2></sdl2>SDL.h>&#xA;&#xA;int main(int argc, char **argv) {&#xA;    SDL_Init(SDL_INIT_AUDIO);&#xA;    SDL_AudioSpec wavSpec;&#xA;    Uint32 wavLength;&#xA;    Uint8 *wavBuffer;&#xA;    SDL_LoadWAV("speaker-test.wav", &amp;wavSpec, &amp;wavBuffer, &amp;wavLength);&#xA;    SDL_AudioDeviceID deviceID = SDL_OpenAudioDevice(NULL, 0, &amp;wavSpec, NULL, 0);&#xA;    SDL_QueueAudio(deviceID, wavBuffer, wavLength);&#xA;    SDL_PauseAudioDevice(deviceID, 0);&#xA;    SDL_Delay(30000);&#xA;    SDL_CloseAudioDevice(deviceID);&#xA;    SDL_FreeWAV(wavBuffer);&#xA;    SDL_Quit();&#xA;    return 0;&#xA;}&#xA;

  



  The above code exhibits the same behaviour of dropping the two additional side channels, despite it being the latest version of SDL that should have supported 7.1 for many releases now. Why might this be happening, and how might I fix it ?