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.. _FFMPEG:

FFMPEG Many video formats and cameras (via ffmpeg)
==================================================

Extensions: ``.mov``, ``.avi``, ``.mpg``, ``.mpeg``, ``.mp4``, ``.mkv``, ``.wmv``

The ffmpeg format provides reading and writing for a wide range
of movie formats such as .avi, .mpeg, .mp4, etc. And also to read
streams from webcams and USB cameras.

To read from camera streams, supply "<video0>" as the filename,
where the "0" can be replaced with any index of cameras known to
the system.

Note that for reading regular video files, the avbin plugin is more
efficient.

By setting the environment variable 'IMAGEIO_FFMPEG_EXE' the
ffmpeg executable to use can be overridden.
E.g. ``os.environ['IMAGEIO_FFMPEG_EXE'] = '/path/to/my/ffmpeg'``
Otherwise, imageio will look for ffmpeg on the system path and then
download ffmpeg if not found.

Parameters for reading
----------------------
loop : bool
    If True, the video will rewind as soon as a frame is requested
    beyond the last frame. Otherwise, IndexError is raised. Default False.
size : str | tuple
    The frame size (i.e. resolution) to read the images, e.g.
    (100, 100) or "640x480". For camera streams, this allows setting
    the capture resolution. For normal video data, ffmpeg will
    rescale the data.
pixelformat : str
    The pixel format for the camera to use (e.g. "yuyv422" or
    "gray"). The camera needs to support the format in order for
    this to take effect. Note that the images produced by this
    reader are always rgb8.
ffmpeg_params: list
    List additional arguments to ffmpeg for input file options.
    Example ffmpeg arguments to use aggressive error handling:
    ['-err_detect', 'aggressive']
print_info : bool
    Print information about the video file as reported by ffmpeg.

Parameters for saving
---------------------
fps : scalar
    The number of frames per second. Default 10.
codec : str
    the video codec to use. Default 'libx264', which represents the
    widely available mpeg4. Except when saving .wmv files, then the
    defaults is 'msmpeg4' which is more commonly supported for windows
quality : float | None
    Video output quality. Default is 5. Uses variable bit rate. Highest
    quality is 10, lowest is 0. Set to None to prevent variable bitrate
    flags to FFMPEG so you can manually specify them using ffmpeg_params
    instead. Specifying a fixed bitrate using 'bitrate' disables this
    parameter.
bitrate : int | None
    Set a constant bitrate for the video encoding. Default is None causing
    'quality' parameter to be used instead.  Better quality videos with
    smaller file sizes will result from using the 'quality'  variable
    bitrate parameter rather than specifiying a fixed bitrate with this
    parameter.
pixelformat: str
    The output video pixel format. Default is 'yuv420p' which most widely
    supported by video players.
ffmpeg_params: list
    List additional arguments to ffmpeg for output file options.
    Example ffmpeg arguments to use only intra frames and set aspect ratio:
    ['-intra', '-aspect', '16:9']
ffmpeg_log_level: str
    Sets ffmpeg output log level.  Default is "warning".
    Values can be "quiet", "panic", "fatal", "error", "warning", "info"
    "verbose", or "debug". Also prints the FFMPEG command being used by
    imageio if "info", "verbose", or "debug".
macro_block_size: int
    Size constraint for video. Width and height, must be divisible by this
    number. If not divisible by this number imageio will tell ffmpeg to
    scale the image up to the next closest size
    divisible by this number. Most codecs are compatible with a macroblock
    size of 16 (default), some can go smaller (4, 8). To disable this
    automatic feature set it to None, however be warned many players can't
    decode videos that are odd in size and some codecs will produce poor
    results or fail. See https://en.wikipedia.org/wiki/Macroblock.


