This app shows information about all media streams inside a video or audio files.

For video streams the app shows: file format name, video codec name and frame size. Also the app the app shows 4 equidistant frames from a video file.
For audio streams: audio codec name, bit rate, number of channels, channel layout, sample rate and format.
For subtitle streams: title and language from stream’s metadata.

Internally the app uses the FFmpeg library and supports all video/audio/subtitle codecs from it.

The READ_EXTERNAL_STORAGE permission is used to actually read data from files that reside on the external storage and to reconstruct the file path.

The source code of the the app and more technical description can be found here: https://github.com/Javernaut/WhatTheCodec