Implementing Reverse effect (playing audio backwards)

Hello everyone. I’m trying to wrap my head around the implementation of Audacity’s Reverse effect. Does anyone know if there’s a restriction on which file types can use this effect? I’ve only been able to play WAV files backwards, but I’d like to use a compressed format.

I’ve downloaded the source, but haven’t dug into it yet. I’d like to have an understanding of potential formatting limitations before I do. I’d appreciate any input or references. Thanks for your help.

interesting. not sure but intuition says that the compression will make playing it backwards different than playing wav backwards and then compressing that to mp3. and then one wonders if playing back a digital wav in reverse is different from playing analog backwards and then digitising that.

Audacity always works with uncompressed audio data. While working with audio, Audacity works in its own “Audacity Project” format, which consists of uncompressed data fragments and an AUP (AUdacity Project) file. See here for more details:

Audio files (of supported types) are imported into Audacity as uncompressed data. The “Reverse” effect simply reverses the data (so that the first sample becomes the last and the last sample becomes the first in the track). After you have worked on a file in Audacity

Audacity natively supports WAV, AIFF, Ogg, FLAC and MP3 for importing. Exporting MP3 files requires that LAME is also installed.

Support for additional file types may be added to Audacity 1.3.x (NOT 1.2.x) by installing FFMPEG.

Out of interest what player do you use that plays (i.e. decodes) WAV files backwards (as opposed to applying a reverse effect on it, then playing the reversed copy forwards)? I think a few players do decode MP3 backwards - Soundplay claimed to be the first to do so.

I don’t know of any editors that edit MP3 directly (as opposed to decompressing it to PCM like Audacity does) that can apply a reverse effect. They will usually be confined to cut/paste and volume changes.

More relevantly, what are you actually trying to achieve?