Why would I convert Opus to AAC instead of keeping Opus?

Opus has near-universal browser support but limited native support on Apple devices outside of Safari and iOS 11+. Older iOS apps, CarPlay units, dedicated media players, and some Bluetooth devices only recognise AAC or MP3. Converting to AAC ensures maximum hardware and software compatibility, at the cost of a slight quality reduction (lossy-to-lossy transcode).

Why can't I convert Opus to AAC directly in the browser?

Browsers expose the Web Audio API for decoding, but they do not ship an AAC encoder. AAC encoding requires platform-licensed codec libraries (such as those in FFmpeg via libfdk_aac or the built-in aac encoder). Running FFmpeg locally handles the full Opus-decode → AAC-encode pipeline without any licensing or browser limitation.

What AAC bitrate should I choose?

64 kbps is decent for speech content like podcasts. 96 kbps is good for general music. 128 kbps is the standard for most streaming services and is transparent for most listeners. 192 kbps is near-lossless on good headphones. For archival, keep your original Opus file — AAC is also lossy.

What is the basic FFmpeg command for Opus to AAC?

ffmpeg -i input.opus -c:a aac -b:a 128k output.m4a. To use the higher-quality libfdk_aac encoder if your FFmpeg build includes it: ffmpeg -i input.opus -c:a libfdk_aac -b:a 128k output.m4a. M4A is the recommended container for AAC — it is an MPEG-4 container identical to MP4 but used exclusively for audio.

Does converting Opus to AAC lose quality?

Yes — this is a lossy-to-lossy transcode. Every re-encode discards additional audio information. The quality loss is generally inaudible at 128 kbps AAC, but if audio fidelity matters, obtain a lossless source (FLAC or WAV) before encoding to AAC.

What container should I use for the output?

Use .m4a (MPEG-4 audio container) for maximum compatibility with Apple devices and iTunes. Use .aac for a raw AAC stream (less common). Avoid .mp4 for audio-only files — it works but media players may display it as a video file with no video track.

Opus to AAC Converter

Name: Opus to AAC Converter
Availability: InStock
Author: Nham Vu

Inspect any Opus file in your browser to see its duration, size, and sample rate — then copy the ready-to-run FFmpeg command to convert it from Opus to AAC.

Audio File Inspector

Drop or select any audio file. It is decoded locally in your browser — no data is uploaded to any server.

Click to select or drag an audio file here

Opus, OGG, MP3, FLAC, WAV, AAC, or any format your browser supports

FFmpeg Command Generator

Input File Name

Also accepts .ogg or any Opus-containing file.

Target AAC Bitrate

ffmpeg -i "input.opus" -c:a aac -b:a 128k "input.m4a"

Install FFmpeg free at ffmpeg.org. Run this command in your terminal after replacing the file name.

Batch convert Opus files (Linux / macOS)

for f in *.opus; do ffmpeg -i "$f" -c:a aac -b:a 128k "${f%.opus}.m4a"; done

Batch convert OGG (Opus) files (Linux / macOS)

for f in *.ogg; do ffmpeg -i "$f" -c:a aac -b:a 128k "${f%.ogg}.m4a"; done

Output File Size Estimator

Enter audio duration below, or inspect a file above to auto-fill.

hrs

min

sec

Formula: bitrate (kbps) × duration (s) / 8000

64 kbps

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96 kbps

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128 kbps

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192 kbps

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256 kbps

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Duration: 3 min 30 sec (210 s)

Why No In-Browser Conversion?

Browsers expose the Web Audio API for decoding audio, but they do not include an AAC encoder. AAC encoding requires licensed codec libraries. FFmpeg handles the full pipeline locally on your machine:

1 FFmpeg opens the Opus OGG container and reads the compressed audio stream.
2 The libopus decoder decompresses the stream to raw PCM audio in memory.
3 The AAC encoder (built-in aac or optional libfdk_aac) re-encodes the PCM data at your chosen bitrate.
4 FFmpeg wraps the AAC stream in an M4A container and writes the output file to disk.

Install FFmpeg at ffmpeg.org (free, open-source). On Linux: sudo apt install ffmpeg. On macOS: brew install ffmpeg.

AAC Bitrate Reference

Bitrate	Quality	Size / min	Best For
64 kbps	Decent	~0.48 MB	Voice, speech, podcasts
96 kbps	Good	~0.72 MB	Casual music listening
128 kbps	Very Good	~0.96 MB	Standard streaming, general use
160 kbps	Excellent	~1.20 MB	High-quality music, good headphones
192 kbps	Near-transparent	~1.44 MB	Audiophile, high-resolution playback
256 kbps	Transparent	~1.92 MB	Apple Music standard, archival AAC

Opus vs. AAC — At a Glance

Opus (RFC 6716, libopus)

Outperforms AAC at most bitrates, especially below 128 kbps
Royalty-free and open-source (Xiph.org / IETF)
Native support in all major browsers and WebRTC
Limited native support on older Apple hardware and dedicated players
Not accepted by Apple Podcasts, iTunes, or most podcast hosts

AAC (Advanced Audio Coding)

Default format for Apple Music, YouTube, and all mobile platforms
Very broad hardware and software support, including car stereos
Accepted by Apple Podcasts, Spotify, and all major podcast platforms
Lower quality than Opus at equivalent low bitrates
Larger file sizes than Opus for the same perceived quality

Copied!

Summary

Inspect any Opus file in your browser to see its duration, size, and sample rate — then copy the ready-to-run FFmpeg command to convert it from Opus to AAC.

How it works

Drop or select an Opus audio file — the file is decoded locally in your browser and never sent to any server.
The Web Audio API reads the file header and reports duration, file size, and sample rate.
Enter your file name and choose a target AAC bitrate in the command generator panel.
Copy the generated FFmpeg command and paste it into your terminal or command prompt.
FFmpeg decodes the Opus stream, re-encodes it as AAC inside an M4A container, and writes the output file.
Play the output file on your target device to verify compatibility before deleting the original.

Use cases

Convert Discord recordings or WebRTC captures from Opus to AAC for iPhone and iPad playback.
Prepare Opus podcast source files for upload to Apple Podcasts, which requires AAC or MP3.
Convert Opus voice memos to AAC for compatibility with older car stereos and Bluetooth speakers.
Batch-convert an Opus library to AAC for syncing with iTunes or Apple Music.
Inspect an unknown .opus or .ogg file to confirm its duration and sample rate before processing.
Generate ready-to-paste FFmpeg commands without memorizing AAC encoder flags.
Re-encode Opus game audio to AAC for use in mobile game projects targeting iOS.
Convert Opus radio streams saved as files into AAC for archival on Apple devices.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu

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