MP4 to FLAC Converter

FLAC, the Free Lossless Audio Codec, was released by Josh Coalson in 2001, joined the Xiph.Org Foundation in 2003 and became an IETF standard as RFC 9639 in 2024. It works like a ZIP file for sound: it packs audio samples smaller and unpacks them to exactly the same numbers. Nothing is approximated, which is what separates it from MP3, AAC and Opus.

The catch is where the samples come from. Nearly every MP4 from a phone, a screen recorder or a website carries AAC, a lossy codec that discarded detail when the video was encoded. Extracting to FLAC decodes that AAC and stores the result losslessly. The sound is identical to what you hear when you play the MP4; it is not better. Anyone who tells you that converting to FLAC upgrades the audio is describing a bigger file, not a cleaner one.

So why do it? Because every lossy re-encode adds its own small damage. If the soundtrack will be edited, mixed, normalized or converted again later, starting from FLAC means only one lossy step in the whole chain: the original one. It is also the right format for camera audio that was recorded as PCM, where FLAC really does keep the full quality at about half the size of WAV.

Keep Sample rate on Same as source. Video sound is almost always 48 kHz, and resampling to 44.1 kHz changes every sample for no benefit unless a device demands it. Bit depth at 16-bit matches what phones and most cameras record. Channels set to Same as source keeps surround tracks intact; FLAC holds up to eight channels.

Windows has played FLAC natively since Windows 10, Android since version 3.1, and the iPhone's Files app since iOS 11. VLC, foobar2000, Plex and most network music players read it too, including its tags. If you need the sound smaller afterward for a phone or a car stereo, FLAC to MP3 makes a single lossy copy from the lossless master, which is exactly the workflow FLAC is good for.