Convert M4B to WAV — Free Online Tool
Convert M4B audiobook files to WAV format, decoding the AAC-compressed audio into uncompressed PCM (pcm_s16le) at 16-bit depth. This is ideal when you need maximum compatibility or want to edit your audiobook audio in a DAW or audio editor without any lossy codec overhead.
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FFmpeg Command
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Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
M4B files store audio encoded with AAC (Advanced Audio Coding), a lossy compression format, inside an MPEG-4 container that also carries chapter markers, bookmarks, and cover art metadata. During this conversion, FFmpeg decodes the AAC audio stream fully — decompressing it back to raw PCM samples — and writes those samples into a WAV container using the pcm_s16le codec (signed 16-bit little-endian PCM). This is a decode-then-repack operation, not a remux: the audio is fully decompressed from AAC into uncompressed audio. The WAV output will be significantly larger than the M4B source because WAV stores every sample without compression. Chapter markers, bookmarks, and cover art from the M4B are not carried over, as the WAV format does not support these features.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, the open-source multimedia processing engine used to decode the M4B's AAC audio and write it into a WAV file. |
-i input.m4b
|
Specifies the input file — an M4B audiobook container holding an AAC-encoded audio stream along with optional chapter markers, bookmarks, and cover art. |
-c:a pcm_s16le
|
Sets the audio codec for the output to pcm_s16le (signed 16-bit little-endian PCM), fully decoding the lossy AAC audio from the M4B into uncompressed samples suitable for the WAV container. |
output.wav
|
Defines the output filename and tells FFmpeg to write the uncompressed PCM audio into a WAV container, the standard format for raw waveform audio compatible with virtually all audio software and devices. |
Common Use Cases
- Loading an audiobook chapter into a DAW like Audacity or Adobe Audition to remove background noise, normalize levels, or apply mastering — DAWs work best with uncompressed PCM source material
- Archiving a purchased M4B audiobook as uncompressed WAV so future re-encodes to any format start from lossless PCM rather than re-compressing already-lossy AAC
- Preparing audiobook narration files for broadcast or podcast distribution platforms that require WAV with specific PCM bit depths
- Splitting a long M4B audiobook into chapter segments using a WAV editor that doesn't support the M4B container or AAC codec
- Running speech-to-text transcription pipelines or audio analysis tools that require raw PCM WAV input and cannot decode AAC-wrapped M4B files
- Importing M4B narration audio into video editing software (such as DaVinci Resolve or Premiere Pro) that handles uncompressed WAV more reliably than AAC-in-M4B
Frequently Asked Questions
The WAV output itself is lossless and uncompressed, but the M4B source was already AAC-encoded, which is a lossy format. This means any quality loss introduced during the original AAC encoding cannot be recovered. The WAV file will be a perfect, uncompressed representation of the decoded AAC audio — no additional quality is lost during this conversion — but it will not be identical to the original pre-encoding audio if you are working with a commercially produced audiobook.
M4B files use AAC compression, which can reduce audio file size by a factor of 10 or more compared to uncompressed audio. WAV with pcm_s16le stores every audio sample as a raw 16-bit integer with no compression at all. A typical M4B audiobook that is 100MB could expand to 600MB–1GB as a WAV file depending on its duration and sample rate. This is expected behavior and reflects the difference between compressed and uncompressed audio storage.
No. The WAV format does not support chapters, bookmarks, or structured metadata beyond basic ID3-style tags. All chapter markers, podcast bookmarks, and cover art embedded in the M4B container are discarded during this conversion. If preserving chapter information is important, consider splitting the M4B by chapter before converting, or using the chapter metadata to manually mark edit points in your WAV editor.
pcm_s16le stands for signed 16-bit little-endian PCM, which is the standard audio format used by CDs and most consumer audio. It provides a dynamic range of about 96 dB, which is more than sufficient for speech-based audiobook content. If you are doing professional audio mastering or need higher precision, you can change the codec in the FFmpeg command to pcm_s24le (24-bit) or pcm_s32le (32-bit), though the original AAC source is unlikely to contain detail beyond 16-bit fidelity.
The displayed command processes a single file, but you can batch-process on your desktop by wrapping it in a shell loop. On Linux or macOS, run: for f in *.m4b; do ffmpeg -i "$f" -c:a pcm_s16le "${f%.m4b}.wav"; done. On Windows Command Prompt, use: for %f in (*.m4b) do ffmpeg -i "%f" -c:a pcm_s16le "%~nf.wav". This will convert every M4B in the current folder to a WAV file with the same base filename.
Yes. To change the bit depth, replace pcm_s16le with another PCM codec such as pcm_s24le for 24-bit or pcm_u8 for 8-bit audio. To resample to a different sample rate, add the flag -ar followed by the target rate, for example -ar 44100 to force 44.1 kHz or -ar 22050 for a smaller file. A full example for 24-bit at 44.1 kHz would be: ffmpeg -i input.m4b -c:a pcm_s24le -ar 44100 output.wav. Without specifying -ar, FFmpeg preserves the sample rate from the source M4B.
Technical Notes
The M4B to WAV conversion involves a full AAC decode pass — FFmpeg uses its built-in AAC decoder to decompress the audio before writing raw PCM samples into the WAV container. The default output codec, pcm_s16le, produces standard CD-quality 16-bit audio and is universally compatible with virtually all audio software, hardware players, and operating systems. The WAV format imposes a 4 GB file size limit due to its 32-bit chunk size header; very long audiobooks at high sample rates could approach this ceiling, in which case switching to a 64-bit WAV variant (using -rf64 auto in FFmpeg) or splitting the file is recommended. Metadata such as title, artist, and album tags from the M4B's iTunes-style atom structure are not automatically transferred to WAV, since WAV metadata support is inconsistent across players — FFmpeg may write some tags, but they are often ignored. The M4B's cover art stream, if present, will also be silently dropped. No re-encoding of video occurs because M4B is an audio-only format; the -c:a pcm_s16le flag is the only codec instruction needed.