Supported Audio Formats

Officially Supported Formats

Leelaa Reader officially supports and guarantees compatibility for the following audio formats:

• .mp3 (Highly recommended, best compatibility)
• .m4a / .m4b (Recommended for audiobooks)
• .flac (Lossless format)
• .wav
• .wma (played through server-side FFmpeg transcoding)

Strictly Unsupported Formats

To ensure stable cross-platform playback and accurate progress tracking, the system strictly does not support the following formats. Even if you force-add these extensions in the backend, the client may fail to play them, or you may experience severe issues like progress jumping or bookmark failures:

• .aac (Raw streams not supported, please encapsulate into .m4a)
• .ogg (Unsupported)
• .opus (Unsupported)

Why are some formats unsupported?

Audiobook platforms have stricter format requirements than standard music players:

1. Duration Accuracy: The system needs the exact audio duration to calculate overall progress and save your last playback position. Formats like raw .aac lack standard headers, making it impossible to retrieve durations quickly and accurately.
2. Cross-Platform Compatibility: We must ensure audio behaves consistently across Web browsers, iOS, and Android clients. .wma relies on server-side transcoding into an MP3 stream; playback will fail if the server has not enabled or detected FFmpeg. Some formats (like .ogg) lack native support in the underlying decoders of certain mobile operating systems.

Web HLS Transcoding Limitations

When the Web player uses HLS for online-transcoded chapters such as .wma or some .m4b files, the mode is intended for compatible playback, not a full local-file playback experience.

Current limitations:

• Fast forward / rewind is not supported
• Arbitrary timeline seeking is not supported
• Buffered progress may not exactly match the range that can be seeked during active transcoding

For reliable fast forward, rewind, and timeline seeking in the Web player, convert the audio to .mp3 or .m4a before importing it.

Format Conversion Recommendations

If you have a large collection of audiobooks in unsupported formats, we recommend batch-converting them before importing them into the system. .wma can be played through real-time server transcoding, but it consumes server CPU; pre-conversion is still recommended on low-powered devices.

Recommended Target Formats: Convert all files to .mp3 (most universal) or .m4a.

Free conversion tools you can use:

• Format Factory: Great for Windows users, supports drag-and-drop batch conversion.
• FFmpeg: Great for advanced users, allows ultra-fast command-line conversion. (e.g., ffmpeg -i input.ogg -c:a libmp3lame -q:a 2 output.mp3)
• XLD (X Lossless Decoder): A lossless conversion tool for macOS users.