ffmpeg_writer.py

"""
A module for writing image arrays directly to video using ffmpeg as a backend.


Slightly edited from the python script by Zulko in the moviepy package, used
under the MIT license.
https://github.com/Zulko/moviepy

The MIT License (MIT)
[OSI Approved License]

The MIT License (MIT)

Copyright (c) 2015 Zulko

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
"""

import subprocess as sp
import os
try:
    from subprocess import DEVNULL  # py3k
except ImportError:
    DEVNULL = open(os.devnull, 'wb')
    

class FFMPEG_VideoWriter:
    """ A class for FFMPEG-based video writing.

    A class to write videos using ffmpeg. ffmpeg will write in a large
    choice of formats.

    Parameters
    -----------

    filename
      Any filename like 'video.mp4' etc. but if you want to avoid
      complications it is recommended to use the generic extension
      '.avi' for all your videos.

    size
      Size (width,height) of the output video in pixels.

    fps
      Frames per second in the output video file.

    codec
      FFMPEG codec. It seems that in terms of quality the hierarchy is
      'rawvideo' = 'png' > 'mpeg4' > 'libx264'
      'png' manages the same lossless quality as 'rawvideo' but yields
      smaller files. Type ``ffmpeg -codecs`` in a terminal to get a list
      of accepted codecs.

      Note for default 'libx264': by default the pixel format yuv420p
      is used. If the video dimensions are not both even (e.g. 720x405)
      another pixel format is used, and this can cause problem in some
      video readers.

    audiofile
      Optional: The name of an audio file that will be incorporated
      to the video.

    preset
      Sets the time that FFMPEG will take to compress the video. The slower,
      the better the compression rate. Possibilities are: ultrafast,superfast,
      veryfast, faster, fast, medium (default), slow, slower, veryslow,
      placebo.

    bitrate
      Only relevant for codecs which accept a bitrate. "5000k" offers
      nice results in general.

    withmask
      Boolean. Set to ``True`` if there is a mask in the video to be
      encoded.
    
    quality
      int, used to set the quality of the video for certain codecs
      for libx264 (default) on a logarithmic scale 0-51, 0 being lossless.
      Default is 23.  18 should be nearly lossless
      
    ffmpeg_params
      list of strings.  Additional command line parameters to pass to ffmpeg,
      e.g. : ['-threads', '1']
    """

    def __init__(self, filename, size, fps, codec="libx264", audiofile=None,
                 preset="medium", bitrate=None, withmask=False,
                 quality=23, ffmpeg_params=None):

        logfile = sp.PIPE

        self.filename = filename
        self.codec = codec
        self.ext = self.filename.split(".")[-1]

        # order is important
        cmd = [
            'ffmpeg',
            '-y',
            '-loglevel', 'error' if logfile == sp.PIPE else 'info',
            '-f', 'rawvideo',
            '-vcodec', 'rawvideo',
            '-s', '%dx%d' % (size[0], size[1]),
            '-pix_fmt', 'rgba' if withmask else 'rgb24',
            '-r', '%.02f' % fps,
            '-i', '-', '-an',
        ]

        if audiofile is not None:
            cmd.extend([
                '-i', audiofile,
                '-acodec', 'copy'
            ])
        cmd.extend([
            '-vcodec', codec,
            '-preset', preset,
        ])
        if codec == 'libx264':
            
            cmd.extend(['-crf', str(quality)])
            
        if ffmpeg_params is not None:
            cmd.extend(ffmpeg_params)
        if bitrate is not None:
            cmd.extend([
                '-b', bitrate
            ])

        if ((codec == 'libx264') and
                (size[0] % 2 == 0) and
                (size[1] % 2 == 0)):
            cmd.extend([
                '-pix_fmt', 'yuv420p'
            ])
        cmd.extend([
            filename
        ])

        popen_params = {"stdout": DEVNULL,
                        "stderr": logfile,
                        "stdin": sp.PIPE}

        # This was added so that no extra unwanted window opens on windows
        # when the child process is created
        if os.name == "nt":
            popen_params["creationflags"] = 0x08000000
        
        self.proc = sp.Popen(cmd, **popen_params)


    def write_frame(self, img_array):
        """ Writes one frame in the file."""
        try:
            self.proc.stdin.write(img_array.tostring())
        except IOError as err:
            ffmpeg_error = self.proc.stderr.read()
            error = (str(err) + ("\n\nMoviePy error: FFMPEG encountered "
                                 "the following error while writing file %s:"
                                 "\n\n %s" % (self.filename, ffmpeg_error)))

            if "Unknown encoder" in ffmpeg_error:

                error = error+("\n\nThe video export "
                  "failed because FFMPEG didn't find the specified "
                  "codec for video encoding (%s). Please install "
                  "this codec or change the codec when calling "
                  "write_videofile. For instance:\n"
                  "  >>> clip.write_videofile('myvid.webm', codec='libvpx')")%(self.codec)

            elif "incorrect codec parameters ?" in ffmpeg_error:

                 error = error+("\n\nThe video export "
                  "failed, possibly because the codec specified for "
                  "the video (%s) is not compatible with the given "
                  "extension (%s). Please specify a valid 'codec' "
                  "argument in write_videofile. This would be 'libx264' "
                  "or 'mpeg4' for mp4, 'libtheora' for ogv, 'libvpx for webm. "
                  "Another possible reason is that the audio codec was not "
                  "compatible with the video codec. For instance the video "
                  "extensions 'ogv' and 'webm' only allow 'libvorbis' (default) as a"
                  "video codec."
                  )%(self.codec, self.ext)

            elif  "encoder setup failed" in ffmpeg_error:

                error = error+("\n\nThe video export "
                  "failed, possibly because the bitrate you specified "
                  "was too high or too low for the video codec.")

            elif "Invalid encoder type" in ffmpeg_error:

                error = error + ("\n\nThe video export failed because the codec "
                  "or file extension you provided is not a video")


            raise IOError(error)

    def close(self):
        self.proc.stdin.close()
        if self.proc.stderr is not None:
            self.proc.stderr.close()
        self.proc.wait()

        del self.proc