mp3 decoder tests

corrupt file test

Sometimes mp3 files can become damaged, and certain players may reject them.
We discover which mp3 decoders can replay damaged files without audible problems

What are the important results of this test?

Lame and CDex are best at decoding corrupt mp3 files.
l3dec may require the command line switches -ign -sa to ignore errors and re-synch after synchronisation loss.

Do we care?!

Sometimes, computer files can be damaged, either by physical damage to the media (e.g. a hard disk crash), or by errors that occur during transmission (e.g. an incorrectly configured ftp client). Mp3 files that sound like they are playing underwater, or are full of bleeps may need Uncook, rather than a different decoder. Files containing ID3v2 tags also cause certain decoders to fail (see our test).

However, damaged mp3 files may contain isolated errors that cause some decoders to crash, or cause occasional bleeps and glitches in the sound. The best decoders here suppressed all bleeps, glitches and skips in our corrupt test file.

How was this test carried out?

A perfectly good mp3 file was loaded into a binary editor. Single bytes, and whole blocks of bytes were changed at random. Some were set to 0, some to 255, others to random numbers. The result was saved, and decoded using the programs under test. The resulting .wav was auditioned, and any audible problems were noted, as shown in the table.

Is this test reliable?

I only used a single artificially corrupted mp3 file. I also used a very subjective ranking system. However, the differences between the various decoders were drastic - if you have a problem file, it's probably worth checking out the two that scored best on this test.

FAQs

I have a file that registers as being 4 minutes long, but only plays for 1 minute. Where is the rest?
Good question! Some VBR files contain a header which tells the player the length of the song. If you only download the first minute of the song, and then loose your connection, the player still reads the header and believes the song is 4 minutes long. After the first minute, it finds the end of the file, and stops.

If someone else has such a file, and you copy the whole file from their hard disk, it's still incomplete because they never downloaded the whole file in the first place.
Where to now?
Go back to the list of tests or go forward to the next test.