Reading/Writing images and videos
=================================

.. currentmodule:: torchvision.io

The :mod:`torchvision.io` package provides functions for performing IO
operations. They are currently specific to reading and writing video and
images.

Video
-----

.. autosummary::
    :toctree: generated/
    :template: function.rst

    read_video
    read_video_timestamps
    write_video


Fine-grained video API
----------------------

In addition to the :mod:`read_video` function, we provide a high-performance 
lower-level API for more fine-grained control compared to the :mod:`read_video` function.
It does all this whilst fully supporting torchscript.

.. autosummary::
    :toctree: generated/
    :template: class.rst

    VideoReader


Example of inspecting a video:

.. code:: python

    import torchvision
    video_path = "path to a test video"
    # Constructor allocates memory and a threaded decoder
    # instance per video. At the moment it takes two arguments:
    # path to the video file, and a wanted stream.
    reader = torchvision.io.VideoReader(video_path, "video")

    # The information about the video can be retrieved using the 
    # `get_metadata()` method. It returns a dictionary for every stream, with
    # duration and other relevant metadata (often frame rate)
    reader_md = reader.get_metadata()

    # metadata is structured as a dict of dicts with following structure
    # {"stream_type": {"attribute": [attribute per stream]}}
    #
    # following would print out the list of frame rates for every present video stream
    print(reader_md["video"]["fps"])

    # we explicitly select the stream we would like to operate on. In
    # the constructor we select a default video stream, but
    # in practice, we can set whichever stream we would like 
    video.set_current_stream("video:0")


Image
-----

.. autosummary::
    :toctree: generated/
    :template: class.rst

    ImageReadMode

.. autosummary::
    :toctree: generated/
    :template: function.rst

    read_image
    decode_image
    encode_jpeg
    decode_jpeg
    write_jpeg
    encode_png
    decode_png
    write_png
    read_file
    write_file
