Start with the missing audio problem
When one video is split into audio.m4s and video.m4s, playing video.m4s alone often gives a video-only fragment. The right workflow is to pair the audio and video fragments first, then export MP4.
If video.m4s needs audio/video pairing, you usually need the matching audio.m4s file. M4S Converter scans local files on Android, batch pairs the fragments, and exports standard MP4 without uploading user files.
When one video is split into audio.m4s and video.m4s, playing video.m4s alone often gives a video-only fragment. The right workflow is to pair the audio and video fragments first, then export MP4.
Local export avoids uploading personal video or audio files to a web converter. It works well for M4S fragments already stored in local folders or a file manager, and the final MP4 can be saved to the gallery.
Use M4S Converter when you have local .m4s files and want to export MP4 on device.
If a related local file set includes audio.m4s and video.m4s, confirm you have permission before pairing and exporting.
Use FFmpeg when you need advanced codec parameters, scripts, or desktop batch workflows.
Only process local files you own or have permission to use.
Best for: Local M4S file processing on Android, audio.m4s/video.m4s pairing, M4S to MP4
Strength: Local scanning, batch pairing, MP4 export, gallery save, no file upload
Limit: Focused on user-authorized local M4S files; not a content online content retrieval tool or streaming tool
Best for: Occasional small files
Strength: No app install
Limit: Requires upload and is weaker for privacy or batch pairing
Best for: Technical users and desktop automation
Strength: Powerful and scriptable
Limit: Command-line setup is harder for ordinary phone workflows
Renaming is not recommended. M4S may be only a media fragment, and audio and video can be separated. Exporting through a conversion or merge workflow is more reliable.
M4S Converter is designed for local file processing, so you do not need to upload your video to an online converter.
Process local M4S files on device with no upload, pair audio.m4s with video.m4s, and export MP4.
Download M4S Converter