[torchcodec] Add a simple example showing how to decode the first fra…

…me of a video (#51)

Summary:
Add a basic example of how to decode a frame from a video.

Pull Request resolved: #51

Differential Revision: D59022932

examples/basic_example.py

@@ -0,0 +1,33 @@
+"""
+==================================================
+Basic Example to use TorchCodec to decode a video.
+==================================================
+"""
+
+# A simple example showing how to decode the first few frames of a video.
+# using the :class:`~torchcodec.decoders.SimpleVideoDecoder` class.
+# %%
+import inspect
+import os
+
+from torchcodec.decoders import SimpleVideoDecoder
+
+my_path = os.path.abspath(inspect.getfile(inspect.currentframe()))
+video_file_path = os.path.dirname(my_path) + "/../test/resources/nasa_13013.mp4"
+simple_decoder = SimpleVideoDecoder(video_file_path)
+# Since `simple_decoder` is an iterable, you can get the total frame count for
+# the best video stream by calling len().
+num_frames = len(simple_decoder)
+print(f"{video_file_path=} has {num_frames} frames")
+
+# You can get the decoded frame by using the subscript operator.
+first_frame = simple_decoder[0]
+print(f"decoded frame has type {type(first_frame)}")
+print(f"{first_frame.shape=}")
+
+last_frame = simple_decoder[num_frames - 1]
+print(f"{last_frame.shape=}")
+
+# TODO: add documentation for slices and metadata.
+
+# %%