MP4 to MKV Converter

What is MP4 to MKV Conversion?

MP4 to MKV conversion is the process of transforming a video file from the standard MPEG-4 Part 14 format into the open Matroska container. Both formats support the same video codecs (H.264, H.265), so conversion is typically performed by remuxing — the video stream is copied bit-for-bit without re-encoding and without quality loss.

MP4 (MPEG-4 Part 14) is an international multimedia container standard with maximum compatibility. MP4 plays on all devices but has limitations in supported audio codecs, subtitles, and number of additional tracks.

MKV (Matroska Video) is a free, open container created in 2002 by the Matroska.org community. MKV has no limits on the number of video, audio, and subtitle tracks, supports styled ASS/SSA subtitles, chapters, embedded fonts, and virtually any codec. It's the preferred format for storing movies with multiple audio tracks and subtitles.

Converting MP4 to MKV unlocks capabilities unavailable in MP4: adding multiple audio tracks (original + dub), styled subtitles, chapter navigation, and embedded fonts.

Technical Differences Between MP4 and MKV Formats

Philosophy and Standardization

MP4 is a commercial standard ISO/IEC 14496-14, evolved from Apple's QuickTime format. Focused on broad compatibility and streaming. Supported at the hardware level by most devices but has functional limitations.

MKV is a completely open and free format without licensing restrictions. Based on EBML (Extensible Binary Meta Language). Focused on maximum flexibility and storing multimedia content with all metadata and additional streams preserved.

Feature Comparison

Compatibility

MP4 wins on compatibility, MKV on functionality. The choice depends on your task.

When MP4 to MKV Conversion is Necessary

Adding Multiple Audio Tracks

MKV's main advantage — unlimited audio tracks in a single file:

• Movies with dubbing — original track + dubbed audio + director's commentary
• Multilingual content — video with audio in multiple languages for international audiences
• Music recordings — concerts with different mix variants (studio, live)
• Educational videos — lectures with translation into multiple languages

MP4 technically supports multiple tracks, but many players and devices only show the first one. In MKV, all tracks are accessible and easily switchable.

Adding Styled Subtitles

MKV supports ASS/SSA subtitles with rich formatting:

• Colored subtitles — different colors for different characters
• Custom fonts — fonts embedded directly in the file
• Positioning — subtitles in different parts of the screen
• Animation — smooth appearance, movement, effects
• Karaoke subtitles — text highlighting in sync with music

This is especially important for anime, where styled subtitles are the standard for quality translation.

Chapter Navigation

MKV supports a full chapter system:

• DVD/Blu-ray movies — preserving original chapters from rips
• Educational courses — quick navigation between sections
• Podcasts and interviews — jumping between topics
• Music compilations — navigating between tracks

Storage Without Codec Restrictions

MKV accepts any codecs, including those not supported by MP4:

• DTS and DTS-HD — high-quality multichannel audio
• FLAC — lossless audio
• Vorbis — free audio codec
• VP8/VP9 — Google video codecs
• Theora — free video codec

Creating Archive Copies

For long-term video storage, MKV is preferable:

• All tracks and subtitles in one file
• No licensing restrictions on the format
• Open specification, not dependent on a single company
• Attachment support (covers, fonts, NFO files)

Conversion Process: What Happens to the File

Scenario 1: Remuxing

If MP4 contains H.264/H.265 video and AAC/AC3 audio — the fastest option:

• Video and audio streams are copied bit-for-bit into MKV container
• Speed — nearly instant
• Quality — 100% preserved, bit-for-bit copy
• Size — remains almost the same

Scenario 2: Audio Re-encoding

If you need to add audio in a format not supported by MP4 (DTS, FLAC):

• Video is copied without re-encoding
• New audio tracks are added in the desired format
• Video quality is 100% preserved

What is Preserved

• Video stream — copied bit-for-bit without changes
• Audio tracks — all tracks from MP4 are transferred
• Duration and proportions — unchanged
• HDR metadata — fully preserved
• Basic subtitles — SRT is transferred

What MKV Adds

• Track capability — additional audio and subtitles
• Chapters — video navigation can be added
• Attachments — subtitle fonts, covers
• Extended metadata — Matroska tags

Typical Use Cases

Creating Multilingual Releases

Combining MP4 video with multiple audio tracks in different languages into a single MKV file. Viewers choose the language during playback.

Adding Subtitles to Movies

Embedding subtitles (SRT, ASS/SSA) directly into the video file. Subtitles travel with the video and aren't lost when copying.

Archiving Video Collections

Converting video collections from MP4 to MKV for storage with full metadata, chapters, and attachments. Open format without licensing restrictions.

Preparing Videos for Media Servers

Media servers (Plex, Jellyfin, Kodi) work excellently with MKV and can stream the right audio track and subtitles to client devices.

Conversion Settings

Mode

• Remuxing — recommended in most cases. Instant, lossless
• Re-encoding — only if you need to change the video codec

Video

With remuxing, the video stream is copied as-is. Re-encoding is not recommended unless there's a specific reason (codec or resolution change).

Audio

• Copy AAC — if source audio is AAC, it transfers unchanged
• Copy AC3 — Dolby Digital is copied bit-for-bit
• Additional tracks can be added after conversion using specialized tools (MKVToolNix)

Comparing MP4 and MKV for Different Tasks

Benefits of MKV Format

Complete Freedom

MKV is an open format without licensing restrictions. Any developer can create MKV tools without royalties or patent risks.

Unlimited Tracks

A single MKV file can contain dozens of audio tracks and subtitles. Viewers choose the audio language and subtitles during playback.

Styled Subtitles

ASS/SSA subtitles with custom fonts, colors, positioning, and animation. Fonts are embedded in the file and don't require installation.

Chapter Navigation

Full chapter system for quick navigation through video content.

Tool Ecosystem

• MKVToolNix — powerful free MKV editor (adding tracks, subtitles, chapters)
• HandBrake — popular converter with MKV support
• FFmpeg — universal tool for MKV operations
• Plex, Jellyfin, Kodi — media servers with excellent MKV support

Tips

Use Remuxing

If you don't need to change the video codec, use stream copy. It's instant and lossless.

Add Tracks via MKVToolNix

After converting to MKV, you can add additional audio tracks and subtitles using the free MKVToolNix tool.

Keep the MP4 Original

MP4 provides better compatibility. Keep it for cases when you need playback on TVs or mobile devices.