AUD · Audio tools

Audio Metadata Viewer

Inspect what is actually inside an audio file. The report covers the container and codec separately, the properties of the audio stream, and any embedded tags.

Container and codec are different layers

The extension names the container, which is the wrapper that holds the encoded stream along with timing and metadata. The codec is what encoded the audio inside it.

That separation explains several things that look like contradictions:

  • .m4a and .mp4 are both MP4 containers, usually holding AAC
  • .ogg is an Ogg container, usually holding Opus or Vorbis
  • .webm holds Opus or Vorbis in a Matroska-derived container
  • .wav is nearly always uncompressed PCM, but the format permits other codecs

An unexpected pairing is worth noting before handing the file to something else, because software that accepts a container does not necessarily support every codec that can appear inside it.

Average bitrate

The bitrate shown is file size divided by duration, not a value read from a header.

Most modern encoders vary their bitrate, spending more on dense passages and less on quiet ones, so a single header figure would describe the encoder’s target rather than the file. The average reflects what the file actually occupies. For uncompressed WAV it will land close to the arithmetic of sample rate times bit depth times channels.

Decodable here

This reports whether the current browser has a decoder for the codec in the file. It is a property of the browser, not of the file.

A file can parse correctly as a container and still fail to decode, which is exactly the failure that stops it loading in other audio tools on the same browser. Checking here first tells you whether the problem is the file or the environment.

Sample rate and channel count

Sample rate is how many measurements per second the recording holds, which sets the highest frequency it can represent: half the sample rate, the Nyquist limit. 44100 Hz reaches about 22 kHz, past the top of adult hearing.

Channel count separates mono from stereo and above. A file reported as stereo can still carry identical content in both channels, which takes twice the space for the same audio. The waveform view draws each channel, so duplicated content is visible as two matching traces.

Tags

Title, artist, and album are read when the container stores them. WAV files frequently carry nothing, since tagging was bolted on later rather than designed in. Tags travel with the file and are not part of the audio, so re-encoding through most tools drops them.

Frequently Asked Questions

It reports the container, codec, duration, sample rate, channel count, file size, average bitrate, whether the browser can decode the track, and any title, artist, and album tags. It reads WAV, MP3, M4A, AAC, Ogg, Opus, FLAC, AIFF, and WebM audio.

It is derived from file size divided by duration, not read from a header field. Variable-bitrate encodings spend different amounts on different passages, so the average is the honest figure and any single header value would not describe the whole file.

Whether this browser has a decoder for the codec in the file. A file can be readable as a container and still fail to decode, which is what stops it working in other audio tools on the same browser.

They are separate layers. A container such as MP4 or Ogg holds a stream encoded by a codec such as AAC or Opus, and the file extension names the container. That is why an .m4a file reports AAC and an .ogg file usually reports Opus or Vorbis.

The file has no embedded tags, or it stores them in a scheme the reader does not cover. WAV files in particular often carry no tags at all, since tagging was never part of the original format.

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