Convert MP4 to FLAC Online
Extract lossless FLAC audio from MP4 video. Maximum quality, no additional loss. Free, in your browser.
.mp4 · up to 100 MB
What you can do
Maximum audio quality from any MP4 video
Sample libraries
Build FLAC sample collections from video for Kontakt, HALion, EXS2, or other samplers.
100% private
Your video never leaves your device. FFmpeg.wasm processes everything in local WebAssembly.
Permanent archival
FLAC is the industry-standard archival format: lossless, open, royalty-free.
DAW without recompression
Bring your video audio to Audacity, Reaper, Ableton, or Logic without any additional recompression.
How it works
Three steps, no hassle
Upload your MP4 file
Drag or select your .mp4 video. Up to 500 MB, no signup.
Decoding and FLAC packaging
FFmpeg.wasm decodes the AAC audio from the MP4 to PCM and repackages it in FLAC with lossless compression. The process runs entirely locally in your browser.
Download your FLAC
FLAC audio ready for Audacity, Pro Tools, DAWs, sample libraries, or permanent archival.
FAQ
Got questions?
No, and this is important to understand with technical precision. Audio in an MP4 recorded with an iPhone, GoPro, or DSLR is AAC-LC, a lossy codec that discards information during encoding. When converting that AAC to FLAC, FFmpeg decodes the AAC audio to PCM (no additional loss at this step) and packages it in a lossless FLAC container. The result is a large file containing exactly the same audio as the decoded AAC — no more, no less. Data that AAC discarded in the original recording is not recovered. The value of FLAC here is different: it guarantees that subsequent conversions and processing in your DAW or audio chain operate on complete PCM data, without any additional lossy recompression.
FLAC and WAV are both lossless, but FLAC compresses PCM data without loss (typically reducing size by 40-60%). Use FLAC when you need to store many samples or audio files extracted from video and space matters: a library of 10,000 samples can be 500 GB in WAV and 250 GB in FLAC. Use WAV when the target software has better compatibility with WAV than FLAC — some older DAWs and VST plugins have issues with FLAC. Pro Tools before 2020 didn't support FLAC natively. Audacity, Reaper, Ableton Live 11+, Logic Pro, and Cubase support FLAC fully.
Yes. Extracting FLAC audio from MP4 videos is a common technique among music producers building custom sample libraries. Nature documentaries, video field recordings, sound effects captured on camera, public domain film dialogue — all can be converted to FLAC and organized in Kontakt, EXS24, SFZ, or any modern sampler. FLAC is accepted as a sample format by Native Instruments Kontakt 5+, Steinberg HALion, Apple Logic EXS2, and most modern software samplers.
FLAC uses compression levels from 0 to 8, where 0 is the fastest compression (larger files) and 8 is maximum compression (smaller files, slower process). Audio quality is identical at all levels — only file size and compression time vary. Convertir.ai uses level 5 by default, the standard recommended by the Xiph.Org Foundation as the optimal point between compression speed and file size.
Yes. FFmpeg detects the sample rate and bit depth of the audio in the MP4 (typically 48 kHz / 16-bit for iPhone video, 44.1 kHz / 16-bit for audio-derived content, 48 kHz / 24-bit for cinema cameras like Blackmagic) and preserves them exactly in the resulting FLAC. No resampling or bit depth conversion occurs unless explicitly requested by the user.
The FLAC will be considerably larger than the MP4 because the MP4 uses very efficient video (H.264 or H.265) and audio (AAC) compression. A 100 MB MP4 can generate a FLAC of 50-200 MB depending on duration and sample rate. For reference: stereo audio at 44.1 kHz / 16-bit in FLAC level 5 takes approximately 3-5 MB per minute (compared to 1-2 MB/min in AAC 192 kbps). For long 1-2 hour videos, the FLAC can be 300-600 MB.
Convert MP4 to FLAC: extract lossless audio from video for archival and music production
Converting MP4 to FLAC allows extracting audio from a video in the world's most widespread lossless compression format, preserving exactly the decoded fidelity of the original AAC audio without any additional degradation. FLAC (Free Lossless Audio Codec) was developed by Josh Coalson and first released in 2001 under a modified BSD license. Specified by the Xiph.Org Foundation, FLAC uses lossless LPC (Linear Predictive Coding) compression to represent exactly the same PCM samples as an equivalent WAV file, but in a file typically 40-60% smaller. It is the standard audio format for high-fidelity music collections, music distribution on specialized stores like Bandcamp and Qobuz, and professional sample libraries for music production. It is important to understand what happens technically: audio in an MP4 is AAC, a lossy codec. When extracting it to FLAC, it is decoded without additional loss and repackaged losslessly. Information that AAC originally discarded is not recovered, but no new degradation is added.
The most valuable use cases for extracting FLAC from MP4 are building sample libraries for music production and permanent archival of valuable audio content captured on video. In sample building: hip-hop, trap, lo-fi, jazz, and electronic music producers regularly extract audio from documentaries (nature, history, science), video concert recordings, camera field recordings, and video-captured sound effects to incorporate as samples in their DAWs. FLAC is the preferred format for sample libraries because it is compatible with the leading software samplers: Native Instruments Kontakt 5 and later, Steinberg HALion 6+, Apple Logic Pro EXS2, Ableton Live 11 (via Simpler and Sampler), and sample map formats like SFZ and EXS. In archival: FLAC with its embedded MD5 checksums and integrity verification capability is the format recommended by the IASA (International Association of Sound and Audiovisual Archives) for audio material preservation in cultural institutions.
Convertir.ai executes FLAC extraction from MP4 entirely in the browser via FFmpeg.wasm. The technical process begins with demuxing the ISOBMFF container to extract the AAC-LC audio stream, which is decoded to 32-bit floating-point PCM samples internally. FFmpeg then applies its native FLAC encoder: it analyzes blocks of samples (4096 samples per block by default), applies LPC (Linear Predictive Coding) predictors to calculate residuals, and encodes those residuals with Rice/Golomb entropy coding. The compression is fully reversible — no samples are lost. Compression level 5 (Xiph standard) produces files approximately 50% smaller than equivalent WAV with about 2-4 seconds of additional processing compared to level 0. Metadata present in the MP4 (title, artist, duration) is transferred to the FLAC VORBIS_COMMENT block. The resulting file can be verified with flac --verify or any FLAC integrity verification tool.