First check that the original plays all the way through on your iPhone. An unsupported codec is only one possible cause. An incomplete transfer, the player, the orientation and the color handling each need a different fix.
The mobile playback fixer checks a file on your device and suggests conversions. It works in your browser and does not send the file to a server. Very large files, or a device with little memory, can still stop it before it finishes. Keep the original and work on a copy.
Before you convert anything
- Play the original on the phone. If it also stops partway, converting it for Windows may not fix it.
- Make sure the whole file is on the PC. Seeing a thumbnail in iCloud does not mean the full video has downloaded. Check the file size and length, or copy it again over USB or through iCloud.
- Try another player that supports the format. If only one app fails, check which formats that app supports. On a work or school PC, ask your administrator before you install anything.
Get codec extensions only from official sources, not from unknown codec packs. Microsoft’s codec FAQ explains how a missing codec differs from other playback problems.
Match the symptom to the next check
| Symptom | Check | Next step |
|---|---|---|
| Codec error | The video codec and what the player supports | Find out whether you need a supported extension or a conversion |
| Sound but no picture | Another player, the video format, whether the whole file transferred | This symptom alone does not show a tag problem |
| Sideways picture | How the player handles orientation | Look at the picture before rotating it |
| Washed-out or dark colors | Whether the source is HDR and the screen supports it | Try a proper HDR-to-SDR conversion |
| Stops partway | The original and the copy on the PC | Check the original and the transfer first |
MOV and MP4 are containers (the wrapper around the video and audio). H.264 and HEVC are formats for the compressed video inside. Renaming .mov to .mp4 does not convert the video. Either container can hold different codecs, so the file extension alone does not tell you whether a player can play it.
Make a Windows-friendly copy
Open the file in the playback fixer and, if needed, choose the H.264 / AAC conversion for Windows. Then play the start, middle and end in the app the recipient will actually use. Check the speech, orientation and colors, not only that a file was saved.
The converted file can be larger than the original. For a smaller copy to share, use the compressor, and compare the result before you delete anything.
Treat HDR separately
Not all 10-bit video is HDR. Converting to 8-bit does not by itself turn HDR into correct SDR. If the result looks washed out or too dark, export to SDR from an editor that handles HDR, or use a correctly set-up tone-mapping step. FFmpeg’s tonemap documentation lists what the input must be.
When a portrait video plays sideways
Some players ignore the orientation information stored in the file. Recording, editing and transfer steps differ, so do not assume every iPhone clip has the same rotation metadata.
Look at the picture in the rotation tool and pick the turn it actually needs. If the picture already looks right, another quarter-turn makes it wrong. Check that people and text are upright, not only that the frame is taller than it is wide.
Record future clips with compatibility in mind
On supported iPhones, Settings > Camera > Formats > Most Compatible records new videos in H.264. See Apple’s instructions. This changes only the video format. It does not mean every recording will have an .mp4 extension, and it does not convert older clips.
Importing and sharing can also change the format, so check the file that actually reached the PC, not only the camera setting.
Questions before changing your files
Do I need to buy an HEVC extension?
It depends on your PC and your player. First find out which codec is missing, and check that the official extension applies to your case. An extension will not fix transfer, orientation or damaged-file problems.
Will changing hev1 to hvc1 always fix a black picture?
No. These tags describe how HEVC is stored in the file. Changing the tag does not add HEVC support to a player that lacks it.
Can I do this on a phone?
Sometimes, if the browser supports the required features and has enough memory. Try a short copy first, and use a computer if processing keeps stopping.
Where can I see a real size comparison?
The compression quality comparison shows measured output sizes, the commands and sample frames. Its source is a clip from a live-action film, not iPhone footage, so your video may shrink by a different amount.
Desktop FFmpeg example
This example is for SDR video. It does not tone-map HDR or repair a damaged file. Write to a new output file so you keep the original.
ffmpeg -i input.mov -map 0:v:0 -map "0:a:0?" -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" -c:v libx264 -preset fast -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart output.mp4The width and height are rounded down to even numbers, which H.264 in 8-bit 4:2:0 needs. The first audio track, if there is one, is converted to AAC; a video with no sound stays silent. FFmpeg rotates the picture automatically by default, so check the result before you add a rotation filter.