Media Formats, Bitrate and File Size
Container and codec are different
MP4 and WebM are containers: they hold streams and timing information. Two MP4 files can contain different video or audio codecs, and one can play on a device while the other cannot. MP3 is an audio format. WAV commonly holds uncompressed PCM audio but is also a container, so the extension alone does not establish its encoding. Public Media Saver's direct-file workflow opens the original file; selecting another quality preference does not rewrite a direct file.
Estimate size before downloading
For a rough decimal estimate, size in megabytes is bitrate in megabits per second multiplied by seconds, divided by eight. A five-minute recording at a total 2 Mb/s is about 75 MB. An audio stream at 128 kb/s for the same duration is about 4.8 MB before metadata and overhead. Variable bitrate, multiple tracks, artwork and container metadata can change the final size. These are arithmetic estimates, not measured download speeds or guaranteed output sizes.
Choose for compatibility, not the largest label
Use a format supported by the device or editor that will open the file. An authorized original MP3 is often convenient for audio playback. A video project may need both video and audio in the same container rather than an audio-only result. Keep an original copy before any conversion performed by another tool. Converting a compressed audio source into WAV can help an editor accept it, but cannot restore details already discarded by the earlier compression.
Resolution is not an upgrade operation
A 720p upload remains limited by its source even if an interface offers a higher quality request. A server may choose a source rendition within a requested limit, but a selector cannot invent genuine detail. The local inspector reports dimensions read from a selected file; it does not upscale, sharpen, transcode or validate a provider's advertising claims. Compare the output dimensions and duration with what you expected before deleting your original copy.
Check the complete result
After saving an authorized file, inspect its size and duration and play a short section at the beginning and end. Confirm that a video file has picture and sound where expected. A very small file named .mp4 can be an error response saved with a misleading extension. An unrecognized result should be checked with a trusted media player and security software, not renamed repeatedly or uploaded to random repair sites.