Why HEVC Phone Videos Don't Always Play, and How to Fix It

Where HEVC footage comes from

Since iOS 11, iPhones have recorded HEVC whenever the camera format is set to High Efficiency, which is the default; the Most Compatible setting records H.264 instead. Recent iPhones also record HDR video by default on supported models, stored as 10-bit HEVC. Many Android phones offer an HEVC or high-efficiency option in their camera settings, though whether it is on by default varies by manufacturer. Drones, action cameras and some mirrorless cameras use HEVC for high-resolution or high-frame-rate modes.

The attraction is size. HEVC was designed to deliver similar picture quality to H.264 at substantially lower bitrates, which matters when a phone records 4K for long stretches. How inter-frame compression achieves that is explained in what a video codec is.

Why an HEVC file plays in one place and not another

HEVC is covered by patent licensing, so not every operating system, browser or app ships its own decoder. Many rely on hardware decoding in the graphics chip, exposed by the operating system. That leads to a patchwork:

• Apple devices running reasonably recent software decode HEVC across the system, including in Safari, on hardware that supports it.
• On Windows, built-in apps and some browsers depend on Microsoft's HEVC Video Extensions, which may be preinstalled on some PCs and need adding from the Microsoft Store on others, along with suitable hardware.
• Chrome and other Chromium-based browsers have supported HEVC playback in recent years where the platform provides hardware decoding, so the same browser can behave differently on two computers.
• Firefox historically did not play HEVC and has been adding support on some platforms in more recent versions.
• Linux support depends on the distribution, drivers and installed codecs.

Support changes with each release, so check the current documentation for your browser and system rather than relying on any list, including this one.

The extra hurdles: 10-bit HDR, tagging and resolution

Even where HEVC plays, particular files can still fail:

• 10-bit and HDR. HEVC Main 10, used for HDR footage, needs a decoder that supports it. Older hardware may handle 8-bit HEVC but not 10-bit, and on standard displays HDR footage can look washed out or too dark when an app does not convert it properly.
• hvc1 versus hev1. HEVC in MP4 and MOV can be labelled with either of two sample-entry tags. Apple's players expect hvc1; a file tagged hev1 may refuse to play in QuickTime or Safari even though the video data is fine. Remuxing with the hvc1 tag fixes it without re-encoding.
• Resolution and frame rate. 4K at 60 fps, or higher, can exceed what an older decoder's level supports.
• Metadata extras. Phone files can include extra tracks or metadata, such as timecode or depth information, that some tools do not expect.

MOV or MP4 with HEVC inside

An iPhone saves HEVC video in a MOV file, while many Android phones use MP4. Both containers come from the same family, and both hold HEVC equally well; the codec, not the container, decides playback in most cases. Where the container does matter, it is usually because a particular app accepts .mp4 but not .mov, or the reverse. In that case a remux, which copies the streams into the other container without re-encoding, solves it in seconds. Simply renaming the extension sometimes works by accident, but it is not reliable; a proper remux rewrites the container correctly. The differences between the two containers in general are covered in MP4 vs MOV.

Diagnosing a file that won't play

1. Check the codec details in MediaInfo: the format (HEVC), profile (Main or Main 10), bit depth, resolution, frame rate and the codec ID, which shows hvc1 or hev1.
2. Try the file in a player with its own decoders, such as VLC. If it plays there, the file is healthy and the problem is the original app's decoder.
3. Try another browser or device. Safari on a recent Mac or iPhone, or a Chromium browser on hardware with HEVC decoding, often succeeds where another fails.
4. If the codec ID is hev1 and Apple software refuses the file, remux with the hvc1 tag.
5. If the file is 10-bit HDR and the target device is older, plan to convert to 8-bit H.264 with tone mapping.
6. For future recordings that need to play everywhere, switch the phone to its most compatible format.

Fixing it: settings, remuxing or converting

Choose the lightest fix that works:

• Change the source. On an iPhone, Settings, Camera, Formats, Most Compatible records H.264 from now on. Settings, Photos, Transfer to Mac or PC, Automatic converts files to a compatible format when copying to a computer over cable, while Keep Originals preserves HEVC.
• Remux. With ffmpeg, ffmpeg -i input.mov -c copy -tag:v hvc1 output.mp4 copies the streams into MP4 with the Apple-friendly tag, without touching the picture.
• Export from Apple software. Recent versions of QuickTime Player's Export As offer a choice between greater compatibility, which is H.264, and a smaller HEVC file.
• Convert with HandBrake, choosing an H.264 preset at a quality that suits the footage.
• Convert with ffmpeg: ffmpeg -i input.mov -c:v libx264 -crf 18 -preset medium -pix_fmt yuv420p -c:a copy output.mp4. The pixel format option matters: without it, a 10-bit source can produce 10-bit H.264, which many players cannot decode.

HDR to standard dynamic range conversion is the hard case. A plain conversion keeps HDR values without mapping them, which often looks flat or washed out. Editors and HandBrake offer tone mapping; check the result on an ordinary screen. Wider conversion options are compared in how to convert video formats.

Trade-offs of converting HEVC to H.264

• Bigger files. For similar quality, H.264 needs a higher bitrate than HEVC, so converted files grow, sometimes considerably.
• A generation of loss. Conversion re-encodes every frame. A high-quality setting keeps the loss small but not zero.
• HDR is lost or altered. Converting to 8-bit standard dynamic range discards the HDR grading unless you carefully re-grade.
• Time. Re-encoding long 4K footage takes a while, especially on laptops without hardware encoders.
• Metadata may be dropped, such as location or camera details, depending on the tool.

Remuxing avoids every one of these costs, which is why it is worth diagnosing before converting.

How mydubly handles HEVC video

mydubly accepts HEVC in MOV, MP4 and the other supported video containers, up to 2 hours per file. The page first opens the file in your browser to read its duration, so the browser must be able to open it; if it reports that it could not open the video, try a browser or device with HEVC support, or convert the file to H.264 first. After that, only the audio is decoded in your browser and compressed audio chunks are sent for transcription and translation. The HEVC picture is never decoded for processing and never leaves your device.

For a translated video, the browser copies the original HEVC frames unchanged next to the translated audio track: the new voice over the original music and effects. HEVC fits in MP4, so the result is normally an MP4; if a video codec cannot go into MP4, the output is MKV instead. Very large files on low-memory devices such as phones may produce the translated audio for download rather than a merged video, as explained in processing large video files in the browser. One consequence is easy to overlook: because the picture is copied, the translated file is still HEVC and has the same playback compatibility as your original. If your audience cannot play HEVC, convert the translated MP4 to H.264 before sharing it. The copying step is described in browser video muxing.

Next step

Check one of your phone clips in a media inspector and note its codec, bit depth and codec ID. If it plays where you need it, translate the original as it is with the video translator; the MOV to text page covers iPhone files for transcripts. If it doesn't, start with the lightest fix above, and if a file is rejected for other reasons, video file not supported walks through the wider checks.