About iSub Player
iSub Player brings local media playback and subtitle learning together.
iSub Player is a local media player designed for language learners and movie lovers. It lets you centrally manage the videos, audio, and subtitles on your device, and learn efficiently with dual subtitles, subtitle delay, and an independent subtitle panel. Built-in AI subtitle analysis, word definitions, online translation, and dictionary lookup help you learn while watching. All media is processed locally on your device for full privacy control.
Features
Capabilities currently supported by iSub Player.
Local Media Library
Import and organize local videos / audio with folders, categories, sorting, and grid / list views.
Multi-format & HDR Playback
Powered by media-kit (libmpv) decoding, supporting mainstream video / audio containers and HDR playback.
Subtitle Playback
Supports embedded subtitle tracks and external subtitle files (.srt / .ass / .ssa / .vtt).
Dual Subtitles
Primary + secondary subtitles shown together, each with independent style and position settings.
Independent Subtitle Panel
Independent subtitle mode, full-screen landscape, custom subtitle list and width for focused study.
Subtitle Delay
Primary / secondary subtitles can each be shifted earlier or later to fix A/V sync issues.
Subtitle StylingPro
Font, size, color, stroke, background, bold, position and more (unlocked with Pro).
Subtitle & Word Favorites
Save subtitles and words into folders, with export / import and cross-device cloud sync.
Single-line LoopPro
Loop a single subtitle line to master difficult passages (unlocked with Pro).
Playback Speed
Multiple speeds from 0.5x to 2.0x, with resume-from-last-position memory.
Background Playback
Audio keeps playing when you switch to another app (iOS background audio / Android foreground service).
Audio Tracks & Playlist
Multiple audio track switching, playlists, and single / sequential loop modes.
AI & Dictionary
AI subtitle analysis, word definitions, online translation (multi-language) and dictionary lookup (Haici / Youdao / Baidu / Merriam-Webster).
Folder LockPro
Set an access password for media folders to protect privacy (unlocked with Pro).
Audio ExtractionPro
Extract audio from a video and save it as an audio file (unlocked with Pro).
Dark ModePro
Eye-friendly dark theme with light / dark / system modes (unlocked with Pro).
Custom ShortcutsPro
Customize playback, subtitle, volume, and brightness shortcuts (unlocked with Pro).
Frequently Asked Questions
Common questions about import, subtitles, Pro, and purchases.
iSub Player decodes via media-kit (libmpv) and supports most common containers such as MP4, MKV, MOV, AVI, FLV, WebM (video) and MP3, M4A, AAC, FLAC, WAV, OGG (audio). Actual support depends on the libmpv decoders available on your device. HDR video is also supported (you can disable HDR in settings to use the standard engine).
It supports embedded subtitle tracks inside videos and external subtitles: .srt, .ass, .ssa, .vtt. You can import external subtitles in the player and load both a primary and a secondary subtitle for dual display.
In the Library tap "Import Media" or "Import Folder", or share a file from the system file manager / photo library to iSub Player. Storage permission is required on Android.
In the player open "Subtitle Settings" β "Import Subtitle" to load a .srt/.ass/.ssa/.vtt file as an external subtitle; then choose primary / secondary to show dual subtitles. Files with a matching name can also be auto-associated with the media.
Make sure the file is not corrupted, the codec is supported, and your OS version meets the requirement. Some codecs (e.g. very high bitrate or unusual containers) may not be supported by the current platform decoder. See "Troubleshooting" below.
Common causes: the subtitle file is not UTF-8 encoded (try re-encoding after import), the subtitle is out of sync with the audio (adjust with "Delay"), or subtitles are hidden. Check that primary / secondary subtitles are enabled in "Subtitle Settings" and that the style color does not blend into the background.
Pro is a one-time purchase for lifetime use and unlocks: no ads, unlimited AI analysis / lookup / favorites, single-line loop, dark mode, custom shortcuts, audio extraction, folder lock, subtitle styling, and custom AI prompts.
On the "Membership Center / Upgrade to Pro" screen tap "Restore Purchase", then sign in with the same Apple ID (App Store in-app purchase) to re-activate Pro. If you used an activation code, re-enter it; if the code is bound to another device, follow the on-screen device migration verification.
Pro is a one-time purchase with no renewal or automatic charges. If you bought it via the App Store in-app purchase and need a refund, request it through Apple's "Purchase History" following Apple's process. For activation-code refunds, contact us via the email below.
Submit via "Settings β Feedback" or "Me β Feedback" in the app, or email isub@hopemach.cn with your device model, OS version, steps to reproduce, and screenshots.
Troubleshooting
If something goes wrong, check the following list step by step.
- Corrupted file: try opening it in another player to confirm the file itself is valid.
- File permissions: on Android grant Storage / Media permission; on iOS allow access when importing from Files.
- Subtitle encoding: subtitles not in UTF-8 may show garbled text or nothing; convert them to UTF-8 with a text editor.
- Video codec: a few very high-bitrate or unusual containers / codecs may not be supported; re-encode to H.264/H.265 MP4 if needed.
- OS version: keep your device OS on a supported version; outdated versions may break decoding or background playback.
- Insufficient storage: importing, extracting audio, or caching needs free space; free up storage and try again.
- Background playback stops: enable "Background Playback" in settings and allow notifications / background activity in system settings (especially the foreground media playback permission on Android 14+).
- Network features limited: AI analysis, online translation, and cloud sync need network; check connectivity and the "API address" setting.
Contact Us
Need help? Feel free to reach out.
Privacy & Terms
We care about your privacy. Related documents below.
App Version
Current version and platform support.
| Current Version | 1.0.0 (Build 6) |
|---|---|
| Platforms | iOS, Android |
| Last Updated | 2026-07-16 |
| Privacy Policy Version | V1.1.0 (effective 2026-06-06) |