Extract Audio from HEVC to M4B — Free Online Tool
Extract audio from HEVC/H.265 video files and save it as an M4B audiobook file, encoded in AAC at 128k bitrate. M4B's chapter and bookmarking support makes it ideal for preserving long-form audio — like a lecture or narrated video — in a format Apple Books, Pocketcasts, and podcast players understand natively.
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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
HEVC (H.265) video files contain both a video stream and one or more audio streams. This tool discards the video stream entirely using the `-vn` flag — no video decoding or re-encoding takes place — and transcodes the audio stream into AAC, the native codec for M4B containers. Because HEVC files often carry audio in formats like AC-3, E-AC-3, or PCM (common in broadcast and camera footage), a transcode to AAC is almost always required rather than a simple stream copy. The output is wrapped in an MPEG-4 container with the `.m4b` extension, which signals to compatible players that the file is an audiobook or podcast, enabling chapter navigation and playback position bookmarking. The `-movflags +faststart` flag moves the MP4 metadata header to the beginning of the file, which improves streaming performance if the file is later served over the web.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In the browser version, this runs via FFmpeg.wasm (WebAssembly), a port of FFmpeg that executes entirely in your browser without sending your HEVC file to any server. |
-i input.hevc
|
Specifies the input HEVC video file. FFmpeg will detect the container format and identify all available streams — including the H.265 video stream and any audio tracks embedded in the file. |
-vn
|
Disables video output entirely. The H.265 video stream from the HEVC file is skipped without being decoded, making this extraction extremely fast even for 4K or 8K source footage. |
-c:a aac
|
Transcodes the audio stream to AAC using FFmpeg's built-in AAC encoder. AAC is the standard and expected codec inside an M4B container and is required for compatibility with Apple Books, Apple Podcasts, and most audiobook players. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second. This is a widely accepted default that balances file size and quality — suitable for speech, narration, and general audio. For audiobook content, 96k is often sufficient; for music, 192k or higher is preferable. |
-movflags +faststart
|
Moves the MP4 container's metadata header (moov atom) to the beginning of the output M4B file. This is essential if the file will be streamed or progressively downloaded, as it allows playback to start immediately without buffering the entire file first. |
output.m4b
|
The output filename with the .m4b extension. The M4B extension distinguishes this file from a generic M4A, signaling to Apple Books, Overcast, Pocketcasts, and other audiobook-aware players to enable chapter navigation and playback position bookmarking. |
Common Use Cases
- Convert a recorded lecture or conference talk shot in H.265 on a modern camera into an M4B so listeners can follow along in Apple Books or Overcast with chapter markers added later using a tool like mp4chaps.
- Extract narration audio from an H.265 screen recording of a software walkthrough and distribute it as an M4B podcast episode compatible with Apple Podcasts.
- Strip audio from an HDR/4K HEVC film commentary track and package it as an M4B so fans can bookmark where they left off while listening in sync with the movie.
- Pull audio from an H.265 dashcam or body-cam recording for archival transcription, using M4B because its AAC encoding offers a good balance of file size and intelligibility.
- Convert a long HEVC-encoded audiobook video (common on YouTube downloads) into a proper M4B file so it integrates with Apple Books' library and remembers your position between listening sessions.
- Extract the audio commentary from an HEVC Blu-ray rip and save it as an M4B to listen on a commute, taking advantage of the format's bookmarking feature to resume exactly where you stopped.
Frequently Asked Questions
Yes, there is a small quality loss because the audio is transcoded from its original codec (often AC-3, DTS, or PCM in HEVC files) into AAC. The default bitrate of 128k AAC is transparent for speech and generally acceptable for most music, but it is not lossless. If the source HEVC file already contains AAC audio, the transcode is still performed — a true stream copy into M4B is only possible when the source audio is already AAC, which you could achieve by adding `-c:a copy` to the command manually.
M4B containers fully support chapters and bookmarking, which is one of the main reasons to choose this format over a plain M4A or MP3. However, HEVC video files (.hevc or .mkv wrapped H.265) rarely carry chapter metadata, so in most cases the output M4B will be a single unbroken audio track. To add chapters, you can edit the output M4B after conversion using tools like mp4chaps or Audiobook Builder, which let you define chapter points manually.
M4B and M4A are both MPEG-4 audio containers using the same internal structure, but the `.m4b` extension signals to Apple devices, Apple Books, Overcast, and other podcast/audiobook players that the file should be treated as an audiobook — enabling bookmarking and chapter navigation. If you rename an M4B to M4A it will still play, but you lose those playback features. Choosing M4B from the start ensures compatible apps handle it correctly without any renaming tricks.
Replace `-b:a 128k` in the command with your desired bitrate. For speech-only content like lectures or audiobooks, `64k` or `96k` AAC is often indistinguishable from 128k and cuts the file size nearly in half. For music or high-fidelity audio, `192k` or `256k` is a better choice. The full modified command would look like: `ffmpeg -i input.hevc -vn -c:a aac -b:a 96k -movflags +faststart output.m4b`.
Yes. On Linux or macOS, you can run a shell loop: `for f in *.hevc; do ffmpeg -i "$f" -vn -c:a aac -b:a 128k -movflags +faststart "${f%.hevc}.m4b"; done`. On Windows PowerShell, use: `Get-ChildItem *.hevc | ForEach-Object { ffmpeg -i $_.Name -vn -c:a aac -b:a 128k -movflags +faststart ($_.BaseName + '.m4b') }`. The browser-based tool processes one file at a time, so the FFmpeg command is particularly valuable for bulk workflows involving many HEVC recordings.
The `-vn` flag instructs FFmpeg to completely ignore the video stream — it is never decoded, and no H.265 decompression work is done on it. This means the conversion is very fast regardless of the video resolution (even 4K or 8K HEVC), because the processing time depends only on the audio stream length and the AAC encoding speed, not on the complexity of the HEVC video. This is one of the fastest operations FFmpeg can perform on a large video file.
Technical Notes
HEVC files encountered in the wild vary considerably in their audio tracks: cameras commonly use PCM or AAC, broadcast sources often carry AC-3 or E-AC-3 (Dolby Digital), and remuxed content may include DTS or TrueHD. All of these require a transcode to AAC for M4B output, since the M4B container's primary supported audio codec is AAC (the tool also supports FLAC and MP3 within M4B technically, but AAC is the standard expected by Apple and most podcast players). The output AAC is encoded using FFmpeg's built-in `aac` encoder at 128k CBR, which is solid for speech but not audiophile-grade; for higher fidelity, `libfdk_aac` (if available in your local FFmpeg build) is generally preferred for its superior quality at the same bitrate. One important limitation: HEVC files with multiple audio tracks (e.g., a director's commentary alongside the main track) will have only the first audio stream extracted by default. To target a specific track, add `-map 0:a:1` (for the second audio stream) before the output filename. Metadata such as title and artist tags from the source HEVC file are passed through by FFmpeg automatically, though HEVC container metadata is sparse compared to MKV or MP4 sources. The `-movflags +faststart` flag is a best practice for any MP4-family file that might be streamed, as it relocates the `moov` atom to the file's head so playback can begin before the full file is downloaded.