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What Is CineX? An iPhone, iPad and Mac App That Turns Videos You Can't Play into MP4

CineX is a video conversion app for iPhone, iPad and Mac. When a local video will not open in common playback situations on those devices, CineX converts it into MP4 so it is easier to open and play. The conversion happens on the device, so the video file itself does not need to be uploaded. Processing time can vary widely because two files with the same extension may use very different video and audio encodings.

It is not a tool that can handle every possible video, and it is not a replacement player for Android or Windows. DRM-protected content cannot be converted, image-based subtitles such as PGS are not preserved, and spatial video is not something you should use CineX to preserve. CineX is aimed at a narrower need: you already have a local video file and want a new MP4 that fits iPhone, iPad and Mac playback situations better.

1. What problem is CineX actually trying to solve?

When a video refuses to open, it is easy to assume the file is broken. Sometimes it is, but another common reason is compatibility: the file may be intact while its container, video encoding or audio encoding does not fit the playback path you are using. The extension at the end of a filename tells you only part of the story. It does not, by itself, determine whether the video can play.

CineX focuses on that distinction. It inspects the content inside the file, then decides how to produce an MP4. The currently device-tested inputs are MKV, MP4, AVI and TS, while the output is always MP4. If you want the underlying idea in plain language, see the difference between a container and a codec.

2. Why can two MKV files take completely different amounts of time?

Because CineX does not decide based on the .mkv extension alone. Two MKV files can contain very different video streams. If the video stream already fits the target MP4, CineX can change the container without compressing the picture again. If the video stream is not suitable, CineX has to perform a full conversion, which takes much longer.

Two files with the same extension can follow different paths: one may only need its container adjusted, while another may require a full conversion.

That is why CineX does not promise that every job finishes immediately. In measured cases, container-only work can finish in seconds, while full conversion is generally measured in minutes. Some high-frame-rate material can take longer still. For a more focused explanation, see container changes versus full conversion.

3. What do you get after conversion?

CineX creates a new MP4 and does not replace the original file. When the picture can be carried over directly, it is not compressed again. When a full conversion is required, the picture is processed again, so it would be misleading to claim that every file keeps identical picture characteristics.

Audio tracks are handled one by one. Tracks that already fit can be kept, while incompatible tracks are converted to AAC. Multiple audio tracks are not collapsed into a single track. Existing text subtitles can also be carried into the MP4, although layout effects in formats such as ASS, including positioning and colors, are reduced to plain text. CineX does not import separate external subtitle files.

There are also clear picture-format limits. If a file needs a full conversion, 10-bit or HDR video is converted to 8-bit, and Dolby Vision metadata is not preserved. When CineX only changes the container, corresponding Dolby Vision metadata and HDR10 static metadata can be retained. The outcome depends on the path the file actually needs.

4. Where does the video conversion happen?

CineX performs the video conversion on the device. Selecting the file, analyzing it and creating the new MP4 are handled on your iPhone, iPad or Mac, and the video file itself does not need to be uploaded.

With CineX, the video conversion runs on the device, and the video file itself does not need to be uploaded.

There is one separate detail worth keeping precise: the free-conversion counter can sync between a user's devices through Apple iCloud Keychain. That means CineX should not be described with an absolute “no network use” claim. The useful privacy boundary is narrower and clearer: the video file itself does not need to leave the device for conversion. See where CineX processes video for the full explanation.

5. How much can you use for free?

The free version includes 5 successful conversions in total. Only successful results count. Failed jobs, canceled jobs and retries do not consume a conversion, and deleting an output does not restore one.

Those 5 conversions are tied to one Apple ID and can sync through iCloud Keychain. When iCloud Keychain is enabled normally, the same count is shared across devices and reinstalling the app does not reset it. If iCloud Keychain is not enabled, the count may differ from one device to another. The detailed rules are in what is free in CineX.

6. What is Opus membership?

Opus membership is a one-time purchase, not a subscription. The current price is US$8.99 in the U.S. store and ¥38 in China. It unlocks one thing: unlimited conversion count.

The free version and Opus membership use the same output quality and processing logic; payment removes the conversion-count limit rather than unlocking a faster or higher-quality mode.

So if you only want to check whether CineX works for the files you have, the free allowance is enough to test it. If this is a recurring need, the one-time purchase removes the count limit. There are no paid picture-quality tiers and no paid speed tiers.

7. Who is CineX a good fit for?

The clearest value of CineX is not a long list of file extensions. It is the way the app turns an awkward compatibility problem into a simple decision: inspect what is actually inside the file, then create an MP4 using the appropriate path. For someone who just wants a video to open, that is more useful than learning a long list of media terms first.

8. Limits: what CineX cannot help with

Full conversion can also require substantial temporary disk space. Peak usage can be around 3 times the source file size; for example, a 10 GB video may require about 32 GB of available space. With very large files, checking free storage before you start is a practical precaution.

Frequently Asked Questions

Is CineX free?

You can use it for free for a total of 5 successful conversions. Failed jobs, cancellations and retries do not count. If you need more, Opus membership is available as a one-time purchase.

Which video formats does CineX support?

The currently device-tested inputs are MKV, MP4, AVI and TS, and the output is always MP4. Formats that have not completed device testing are not presented here as supported capabilities.

Will conversion reduce picture quality?

It depends on the processing path. When CineX only changes the container, the picture is not compressed again. When a full conversion is required, the picture is processed again, and 10-bit or HDR material is converted to 8-bit.

Does CineX have an Android or Windows version?

No. CineX currently runs on iPhone, iPad and Mac. There is no Android, Windows, web or Vision Pro version.

How long does one conversion take?

There is no single answer. If the video stream already fits the target MP4, the job can be measured in seconds. A full conversion usually takes minutes, and some high-frame-rate material can take longer.

Axiom One LLC — CineX. Figures current as of 24 September 2026.