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Intermediate

Keep Subtitles When Converting MKV to MP4

Master subtitle preservation during MKV to MP4 conversion. Learn mapping techniques, format compatibility, and troubleshooting for perfect subtitle integration.

Subtitle Mapping
Format Compatibility
FFmpeg Commands

Tutorial Overview

MKV files often contain multiple subtitle tracks in various formats (SRT, ASS, VobSub, PGS). When converting to MP4, you need to carefully map these streams to ensure compatibility and proper playback.

~10 min
Reading Time
FFmpeg
Primary Tool
Cross-platform
Compatibility

1
Analyze Your MKV File

First, examine your MKV file to identify available subtitle streams:

Command
ffprobe -v quiet -print_format json -show_streams input.mkv

This command displays all streams including subtitle tracks with their codecs, languages, and index numbers.

2
Basic Subtitle Preservation

To copy all subtitle streams during conversion:

Basic Copy Command
ffmpeg -i input.mkv -c copy -c:s mov_text output.mp4

3
Selective Subtitle Mapping

To include specific subtitle tracks:

Selective Mapping
ffmpeg -i input.mkv -map 0:v -map 0:a -map 0:s:0 -map 0:s:1 -c copy -c:s mov_text output.mp4

Stream Mapping

  • -map 0:v - Video stream
  • -map 0:a - Audio stream
  • -map 0:s:0 - First subtitle
  • -map 0:s:1 - Second subtitle

Common Formats

  • SRT → mov_text
  • ASS → mov_text
  • VobSub → Not compatible
  • PGS → Not compatible

4
Advanced Subtitle Options

Fine-tune subtitle handling with advanced options:

Set Default Subtitle
ffmpeg -i input.mkv -c copy -c:s mov_text -disposition:s:0 default output.mp4
Add Subtitle Metadata
ffmpeg -i input.mkv -c copy -c:s mov_text -metadata:s:s:0 language=eng -metadata:s:s:1 language=spa output.mp4

Common Issues & Solutions

Issue: "Subtitle codec not supported"

Some subtitle formats (VobSub, PGS) aren't compatible with MP4.

ffmpeg -i input.mkv -vf "subtitles=input.mkv" -c:a copy output.mp4

Burns subtitles into video (permanent)

Issue: Subtitles not displaying

Player might not support mov_text format.

ffmpeg -i input.mkv -c copy -c:s srt output.mp4

Use SRT format for better compatibility

Pro Tips

  • Always check subtitle compatibility before conversion to avoid quality loss
  • Use -disposition:s:0 default to set the primary subtitle track
  • Test output files on your target playback device to ensure subtitle support
  • Consider extracting subtitles as separate SRT files for maximum compatibility

Ready to Convert with Subtitles?

Apply what you've learned with our free online MKV to MP4 converter. Preserve your subtitles while converting directly in your browser.

Start Converting with Subtitles

Browser-based • No uploads • Keep your subtitles • Free forever