Audio Codec Tag Not Supported? Find Your Number Here

If a program has told you it cannot handle a particular audio codec tag, the number it gave you is a lookup key - and the first thing worth knowing is that the same codec has two different numbers.

Every audio format that Windows recognises carries a registered tag number stored inside the file.

When something cannot decode a stream, that number is usually what it reports.

The table below turns any of those numbers into an answer, and the section under it covers the one install that handles nearly all of them.

Why your number may not seem to be listed

This trips up almost everybody, and it is the reason these tags look more complicated than they are.

The same tag gets written in two number systems. MP3 is tag 0x0055 in hexadecimal, which is 85 in ordinary decimal. Those are not two codecs with a problem each - they are one codec, and which form you see depends on which program showed you the error.

The lookup table

Notice how often the answer is the same. That is not laziness in the table - it is the actual state of things, and it points at the shortcut.

The one install that covers most of this

These tags date from an era when Windows expected a separate small codec to be installed for every format, and each of the entries above once had its own download.

That is not how playback works now. A single modern decoder set handles the whole list, which is why chasing individual codecs usually ends at an abandoned download page for something last updated fifteen years ago.

If you would rather have a player and a renderer bundled in at the same time, the K-Lite Codec Pack includes those same decoders. Our guide to the best codec packs compares the options if you want to choose deliberately.

The cases where a specific codec is still the answer

Three situations genuinely call for an individual codec rather than a decoder set, and all three involve older software rather than playback.

• Editing rather than playing. Tools like VirtualDub use the older ACM interface directly, so they need a codec installed that way regardless of what your player has.
• Encoding to an old format. Decoders let you play a format; encoding to it needs the codec that can write it.
• A single stubborn file. Occasionally one stream defeats the general-purpose decoder and the original codec handles it.

For those cases the relevant individual codecs are the MPEG Layer-3 Decoder for MP3 and AC3 Filter for Dolby Digital.

VoxWare MetaSound covers the two VoxWare tags, which are the only entries in the table with no modern equivalent at all.

For Ogg Vorbis there is a standard Ogg Vorbis codec and an MSACM version for software that needs the older interface specifically.

If your tag is not in the table

The registered list runs to hundreds of entries, most of which nobody has encountered in twenty years. The table above covers what actually turns up.

Rather than hunting a number, it is usually faster to read the file and find out what is really inside it.

• In the browser. Drop the file into our Codec Finder, which names the codecs and container without uploading anything.
• On the desktop. MediaInfo reports the same detail plus everything else about the streams.

Knowing the format name rather than the tag number makes the answer much easier to find, and it tells you whether the problem is the audio at all. If the distinction between a container and a codec is new, containers and codecs covers it.

Quick questions

Find your number in either column, and if the answer says LAV Filters - which it usually will - that one install ends the search.

Download LAV Filters to cover the whole table at once, or leave a comment with the tag number you were given if it is not listed here.

The individual codecs all sit in the Audio Codecs section.