Convert CAVS to ALAC — Free Online Tool
Convert CAVS video files to ALAC audio, extracting the audio stream from Chinese Audio Video Standard broadcasts and encoding it losslessly using Apple's ALAC codec inside an MPEG-4 container. Ideal for archiving broadcast audio with perfect fidelity for playback in iTunes, Apple Music, or any Apple device.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your CAVS file here
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Settings
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
CAVS files contain video encoded with H.264 (libx264) and audio encoded with AAC — a lossy codec. During this conversion, the video stream is discarded entirely since ALAC is a pure audio format. The AAC audio is decoded back to raw PCM and then re-encoded using Apple Lossless Audio Codec (ALAC), which compresses the audio without any quality loss relative to the decoded PCM signal. Because this is a lossy-to-lossless pipeline, it's important to understand that the original AAC encoding has already introduced some quality reduction; ALAC will faithfully preserve the decoded audio as-is, but cannot restore detail lost during the original AAC compression. The result is a .m4a file that is bit-perfect from the decoded source onward.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool — in this browser-based tool, it runs as FFmpeg.wasm compiled to WebAssembly, so no files leave your device. The same command works identically on a desktop FFmpeg installation. |
-i input.cavs
|
Specifies the input file — a CAVS-format video file containing an H.264 video stream and an AAC audio stream conforming to the Chinese national broadcast standard. |
-c:a alac
|
Sets the audio codec to ALAC (Apple Lossless Audio Codec). This instructs FFmpeg to decode the source AAC audio from the CAVS file to PCM and re-encode it losslessly using ALAC, preserving all decoded audio data with no further quality loss. |
-c:a alac
|
This flag appears twice in the resolved command, which is redundant but harmless — FFmpeg will honor the last-specified codec for the audio stream, which is alac. In practice, a single -c:a alac is sufficient, but the duplicate does not affect the output. |
output.m4a
|
Defines the output filename with the .m4a extension, which tells FFmpeg to wrap the ALAC-encoded audio in an MPEG-4 container. The .m4a extension is the standard container for ALAC and ensures compatibility with iTunes, Apple Music, and Apple devices. |
Common Use Cases
- Archiving audio from Chinese broadcast television recordings (CAVS format) into a lossless format for long-term preservation without further generational quality loss
- Importing audio from CAVS content into iTunes or Apple Music for a permanent, high-quality library copy that syncs to iPhone or iPad via ALAC support
- Extracting speech or narration from CAVS educational or documentary content into ALAC for use in Apple-based audio editing workflows like Logic Pro
- Preserving the audio track of a CAVS broadcast at the highest fidelity possible before further processing or format conversion in a mastering chain
- Converting CAVS audio to ALAC so it can be stored alongside other lossless music files (FLAC, WAV) in a curated hi-fi library while maintaining Apple ecosystem compatibility
Frequently Asked Questions
ALAC itself is lossless, meaning it introduces zero additional quality degradation during encoding. However, the audio inside a CAVS file is originally compressed as AAC, which is a lossy codec. The conversion decodes the AAC audio to PCM and then re-encodes it with ALAC losslessly — so what you get is a perfect lossless copy of the decoded AAC, not the original uncompressed audio. Any quality loss from the initial AAC encoding in the CAVS file is already baked in and cannot be recovered.
ALAC is specifically an Apple format stored inside an MPEG-4 container, which uses the .m4a file extension. This is the standard and correct container for ALAC audio — it provides full compatibility with iTunes, Apple Music, QuickTime, and all Apple devices. If you need lossless audio in a different container, you would choose a different target format like FLAC (.flac) or PCM WAV (.wav).
ALAC inside the MPEG-4 container (.m4a) does support chapters, and FFmpeg can write chapter metadata to this format. However, CAVS files do not support chapters, so there is no chapter data in the source file to carry over. The output .m4a will not contain chapters unless you add them manually after conversion.
The video stream is completely dropped. ALAC is a pure audio format and the .m4a container used here carries no video. FFmpeg extracts only the audio track from the CAVS file and discards the H.264 video entirely. If you need to keep the video, you would need to target a video-capable output format instead.
The command shown processes one file at a time, but you can run it in a shell loop to batch convert. On Linux or macOS, use: for f in *.cavs; do ffmpeg -i "$f" -c:a alac "${f%.cavs}.m4a"; done. On Windows Command Prompt, use: for %f in (*.cavs) do ffmpeg -i "%f" -c:a alac "%~nf.m4a". This is especially useful for processing large batches of CAVS broadcast recordings locally, particularly files over 1GB that exceed the browser tool's limit.
ALAC losslessly compresses PCM audio, typically achieving 40–60% of the size of uncompressed WAV. However, when compared to the original AAC audio track inside the CAVS file, the ALAC output will usually be significantly larger — often 3–5x bigger — because AAC is a highly efficient lossy codec that discards audio data to achieve small file sizes, while ALAC retains all decoded data. Expect your .m4a file to be noticeably larger than the audio portion of the source CAVS file.
Technical Notes
CAVS (Chinese Audio Video Standard, GB/T 20090) is a Chinese national broadcast standard that uses H.264 for video and AAC for audio. Because AAC is a lossy codec, any CAVS-to-ALAC conversion is technically a transcode through a lossy stage — the ALAC output is lossless from the point of decode onward but does not represent a lossless copy of the original recording. ALAC stores audio in an MPEG-4 container (.m4a) and is natively supported by all Apple platforms including iOS, macOS, tvOS, iTunes, Logic Pro, and GarageBand, as well as many Android players and desktop applications. One limitation to note: ALAC does not support multiple audio tracks, so if a CAVS file contained more than one audio stream, only the default stream would be extracted. Metadata tags (artist, title, album) are supported in the MPEG-4 container and can be added post-conversion using tools like Kid3 or MP3Tag. The MPEG-4 container's chapter support is present but irrelevant here since CAVS sources carry no chapter data.