Embed Subtitles
Add a text file (.SRT) inside your video container.
How to embed an SRT subtitle file into your video in 3 steps
Import Video
Select the main video file (MP4 format) intended to receive the structural text translation.
Load .SRT File
Upload your standardized subtitle file in .srt format containing the precise time markers.
Multiplexing
Click on Merge. The script securely encapsulates the text channel into the video container locally.
The technical advantage of stream multiplexing (Soft Sub) for video subtitling
Adding subtitles has become a critical step to maximize the accessibility of your audiovisual media assets, especially across social networks or e-learning platforms where a vast majority of active viewers watch clips completely muted. However, traditional hardcoding (Hard Sub) requires re-encoding the entire video track—a long computational task that degrades image clarity and locks text displays permanently. Our web tool utilizes an advanced alternative: stream multiplexing (Soft Sub).
By harnessing the cutting-edge capabilities of FFmpeg compiled via WebAssembly, the application performs a purely browser-level software merge. The -c copy instruction orders the engine to duplicate the original audio and video streams identically without any pixel loss, while the -c:s mov_text parameter translates the .srt track into a text-based subtitle track encapsulated independently inside the MP4 container. The operation runs offline in less than a second with zero cloud exposure.
Frequently Asked Questions
What is the difference between Soft Sub and Hard Sub subtitles?
Hard Sub burns text strings directly onto the video pixels permanently. Soft Sub (used here) injects subtitles as an adjustable metadata channel. This allows the audience to toggle them on or off inside their preferred media player settings layout.
Why does the merging process complete in just a few seconds?
Because the script mirrors the input data streams directly without recalculating complex graphics matrices (-c copy), the process is limited to rapid binary stream mapping, preserving your device's processing capacity.