Convert Advanced Systems Format (.asf) to Advanced Audio Coding (.aac) online for free. Fast, secure video conversion with no watermarks or registration.
Conversion settings — add a file to adjust
Upload your .asf file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .aac file when it's ready.
ASF containers frequently carry WMA (Windows Media Audio) streams alongside video. AAC (Advanced Audio Coding) is the successor to MP3 and the default audio format for iTunes, YouTube, and most modern devices. Converting ASF to AAC extracts the audio track from the Microsoft container and re-encodes it into the widely supported AAC-LC codec, discarding the video stream entirely.
WMA audio trapped inside ASF files is poorly supported outside Windows. macOS, iOS, and most Linux music players handle AAC natively but not WMA. AAC also delivers better audio quality than WMA at equivalent bitrates, making it a technical upgrade. If you need just the audio from an ASF recording — a podcast, lecture, or music track — AAC is the most portable choice.
FFmpeg reads the ASF container, identifies the audio stream (typically WMA v2, WMA Pro, or WMA Lossless), and transcodes it to AAC-LC using the libfdk_aac or native AAC encoder. The output is wrapped in an ADTS or M4A container. Sample rates of 44.1 kHz or 48 kHz are preserved. Channel layout (stereo/5.1) can be downmixed to stereo if needed.
AAC at 192 kbps matches or exceeds WMA at 192 kbps in listening tests. For speech-only ASF content, 96-128 kbps AAC is transparent. Music benefits from 192-256 kbps. If the original WMA was encoded at a very low bitrate, converting to AAC will not improve quality — you cannot add detail that was already discarded.
| Device | ASF | AAC |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Native |
| iPhone/iPad | Partial | Native |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: 1920x1080
Bitrate: 8-12 Mbps
H.264 recommended for fast processing
Resolution: 1080x1080
Bitrate: 3.5 Mbps
Square or 9:16 for Reels
Resolution: 1080x1920
Bitrate: 4 Mbps
9:16 vertical, under 60s ideal
Resolution: 1280x720
Bitrate: 5 Mbps
Under 140s, 512MB max
Resolution: 960x540
Bitrate: 2 Mbps
16MB limit for standard, 64MB for document
Resolution: 1280x720
Bitrate: 4 Mbps
Extracting AAC audio from ASF files frees your audio from Microsoft's ecosystem and puts it in a format that plays everywhere, from iPhones to car stereos to web browsers.
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Fungerar overallt
| No |
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| Funktion | ASF | AAC |
|---|---|---|
| Fullstandigt namn | Advanced Systems Format | Advanced Audio Coding |
| Filandelse | .asf | .aac |
| Bast for | Streaming optimized | Superior to MP3 |