Understanding Codecs in MX Player
A codec (coder-decoder) is software that compresses and decompresses video and audio data. When MX Player can't play a file, it's often because the required codec isn't available or the decoder mode is incompatible. Understanding how codecs work in MX Player helps you fix issues fast.
Built-In vs. Custom Codecs
MX Player comes with built-in codec support for most common formats. However, for some formats — particularly AC3 (Dolby Digital), DTS, and certain HEVC/H.265 profiles — you need to install a custom codec package.
Custom codecs are separate apps available on the Play Store:
- Search for "MX Player Codec" on the Play Store.
- You must install the version matching your device's CPU architecture.
- To check your architecture: Settings > About Phone > Processor (look for ARM, ARM64, or x86).
After installing the codec app, restart MX Player. It will automatically detect and use the new codec.
Supported Video Formats
| Format | Container | Notes |
|---|---|---|
| H.264 / AVC | MP4, MKV, AVI | Natively supported, best compatibility |
| H.265 / HEVC | MP4, MKV | Requires HW+ or custom codec on older devices |
| VP9 | WebM, MKV | Supported in SW mode |
| AV1 | MKV, WebM | Support depends on device and app version |
| DivX / Xvid | AVI | Supported via SW decoder |
| MPEG-2 | TS, VOB | Supported via SW decoder |
Supported Audio Formats
| Format | Notes |
|---|---|
| AAC | Native support |
| MP3 | Native support |
| FLAC | Native support |
| AC3 / Dolby Digital | Requires custom codec |
| DTS | Requires custom codec |
| TrueHD / Atmos | Limited support; pass-through may be needed |
Subtitle Formats Supported by MX Player
MX Player has one of the most comprehensive subtitle engines on mobile. Supported formats include:
- SRT (.srt) – The most common, widely supported
- SSA / ASS (.ssa, .ass) – Advanced styled subtitles with formatting
- SUB / IDX – DVD-style image-based subtitles
- PGS – Blu-ray bitmap subtitles (requires SW decoder)
- SMI (.smi) – Common in Korean media
- TTML / DFXP – XML-based subtitle formats
How to Customize Subtitles
To access subtitle settings during playback, tap the subtitle (T) icon. From there you can:
- Change font size and font face
- Adjust text color and background opacity
- Set the subtitle position (drag it anywhere on screen)
- Fix timing by swiping the subtitle text left (delay) or right (advance)
- Change text encoding if characters appear garbled
Hardware vs. Software Decoding: Which Should You Use?
Use HW (Hardware) when: Playing H.264 or H.265 content on modern devices. It's faster and saves battery.
Use SW (Software) when: HW fails to play the file, you need AC3/DTS audio, or you're using complex ASS subtitles that require software rendering.
Use HW+ when: Your device supports it and you're playing HEVC/H.265 content — this mode often gives the best balance of performance and compatibility.