Convert MP3 to AT3

Some PSP game tools, homebrew utilities, and older Sony software require audio stored as .at3 rather than MP3. The required file usually has to match the target's ATRAC codec, sample rate, channel layout, bitrate, and RIFF-based container structure.

MP3 and AT3 formats

MP3 is a lossy compressed audio format used for music downloads, podcasts, voice recordings, media libraries, players, phones, and web audio. It is broadly supported, but its encoded audio is not suitable for software that specifically expects Sony ATRAC data.

AT3 commonly refers to a file with the .at3 extension containing Sony ATRAC3 or, in some cases, another ATRAC-family stream in a RIFF/WAVE-style container. ATRAC3 was used by older Sony products and software, including Memory Stick and MiniDisc-era applications, as well as some PlayStation and PSP game assets.

ATRAC3 was designed to store audio at relatively low fixed bitrates, commonly 66, 105, or 132 kbps. Its practical advantage is compatibility with software built for ATRAC, not better sound quality or broader device support than MP3. ATRAC3 and ATRAC3plus are distinct codecs; an .oma file or an ATRAC-family file from SonicStage is not necessarily usable where a RIFF-based .at3 file is required.

Check the target requirements first

Inspect the target program's documentation or a known-working original AT3 file before converting. Record its codec, sample rate, channel count, bitrate, duration, and, for game assets, encoded size. Many PSP-related tools use 44,100 Hz stereo input, but that is not a universal AT3 requirement.

Do not change song.mp3 to song.at3 by renaming it. Renaming does not convert the MP3 bitstream, add an ATRAC encoder header, or create the RIFF structure expected by the target.

Convert with an ATRAC3-capable desktop encoder

ATRAC3 encoding is now uncommon because Sony discontinued the consumer ATRAC ecosystem. Use an older Sony Creative Software-era release of Sound Forge only if its installed format list explicitly includes ATRAC3 or AT3 export; current software editions and installations vary, and many do not provide that encoder.

1. Open the source file through File → Open.
2. Match the required audio properties. In compatible Sound Forge versions, use Process → Resample to set the required sample rate and Process → Channel Converter to set mono or stereo.
3. Select File → Save As and choose the available ATRAC3 or AT3 format.
4. Select the bitrate required by the target, then save the file as output.at3.
5. Test the output in the exact game tool, device, emulator, or application before batch conversion.

Some legacy PSP conversion utilities can create AT3 files when used with a legitimately installed ATRAC codec component. Follow the utility's documentation and avoid downloading individual codec DLLs from unverified sources. A utility that only decodes ATRAC or merely wraps audio in another container cannot produce a compatible ATRAC3 file.

Prepare WAV input when required

Legacy encoders often accept PCM WAV more reliably than MP3. FFmpeg can decode MP3 and create an appropriate intermediate WAV, but standard FFmpeg builds generally cannot encode ATRAC3.

ffmpeg -i "input.mp3" -ar 44100 -ac 2 -c:a pcm_s16le "input.wav"

This creates 44.1 kHz, stereo, 16-bit PCM WAV. Change -ar or -ac only when the target requires different values, then provide input.wav to the ATRAC3-capable encoder.

Online services and compatibility limits

Do not rely on a general online converter unless it explicitly documents ATRAC3 encoding and RIFF-based .at3 output. Reputable mainstream conversion services rarely provide verified ATRAC3 export, so an online file labeled AT3 may use the wrong codec or container. Desktop conversion with a confirmed encoder is safer for proprietary game or device formats and avoids uploading private audio.

MP3-to-AT3 conversion is lossy-to-lossy transcoding: it cannot restore audio discarded by MP3 encoding and can add further artifacts. When possible, encode AT3 once from the original WAV, AIFF, FLAC, or other lossless source rather than from an MP3.

A valid AT3 file can still fail in a game if the engine expects a particular bitrate, duration, block layout, archive offset, or additional packing step. Replacing game audio may require rebuilding the game's sound archive after conversion.