Extract supported MP4 audio and encode it as MP3 while retaining its audio timeline and avoiding video re-encoding.
Drag and drop one or more files, or choose files from your device.
Supported: .mp4 · up to 3 sources · 50 MiB per source. Existing codec, duration, pixel and memory limits apply.
Existing native decoding, codec, bitrate, channel/sample-rate policy, clipping-headroom and independent audio verification. Jobs remain sequential with the original decoder/encoder cleanup.
Enter your values locally; no inputs are uploaded.
Check validation feedback before reviewing the browser-generated result.
Review the explanation, copy supported outputs or reset the workspace.
Choose a supported local file, review its detected codec and stream information, adjust settings, convert and play or inspect the verified output before downloading.
Extract supported MP4 audio and encode it as MP3 while retaining its audio timeline and avoiding video re-encoding. Measured conversion progress, bounded processing, cancellation, local previews and output codec checks support a practical private workflow.
Files, filenames and media data stay in browser memory. There are no conversion uploads, external conversion APIs, source-content analytics or storage persistence. Downloads require an explicit action; reset/unmount revokes owned media URLs and closes processing resources. Source metadata tags are not copied.
No. Only the supported audio track is decoded and encoded as MP3. Video packets are not decoded or re-encoded by the extraction engine, so video processing does not add a generation or unnecessary codec work.
The verified subset is one native-decodable AAC or MP3 audio track. Multiple audio tracks, unsupported audio codecs and DRM/encrypted tracks are rejected rather than silently choosing or misrepresenting them.
The file is inspected before conversion and a clear no-audio error is shown. A fake silent MP3 is not generated as a substitute for a missing source stream.
Decoded audio timestamps are retained on the standalone audio timeline, including leading silence for positive source offsets. Negative codec-priming samples are trimmed appropriately. MP3 encoder padding can still add a small documented duration difference.
Yes. Choose 128, 192, 256 or 320 kbps CBR. Common sample rates and original mono/stereo are retained, with explicit resampling warnings for rates outside the supported MP3 range.
No. The audio is encoded into lossy MP3, and timing can include encoder/decoder priming and frame padding. Output decoding, bitrate/configuration, duration, non-silence and clipping checks run before a download is offered.
Extract supported MP4 audio and encode it as MP3 while retaining its audio timeline and avoiding video re-encoding.
No. Only the supported audio track is decoded and encoded as MP3. Video packets are not decoded or re-encoded by the extraction engine, so video processing does not add a generation or unnecessary codec work.
Native browser decoding and local LAME MP3 encoding are used where applicable. MP3 is lossy; PCM output retains the intended decoded samples subject to chosen transformations/quantization. Codec priming and frame padding can affect duration by about 0.1 seconds.
Media engines load on demand when a file is processed. LAME encoding uses a small bundled WASM extension; no FFmpeg engine is downloaded by the application. Inputs are bounded to 50 MiB and supported streams to 180 seconds. Measured progress, cancellation, output decoding and previews help verify real results. Source files and filenames are not uploaded, logged or persisted.