video captured from iphone gets rotated when converted to .mp4 using ffmpeg

For sake of completeness, the reason this is happening is that iPhones only actually capture video in one fixed orientation. The measured orientation is then recorded in Apple-specific metadata.

The effect is that Quicktime Player reads the metadata and rotates the video to the correct orientation during playback, but other software (e.g., VLC) does not and shows it as oriented in the actual codec data.

This is why rotate=90 (or vflip, or transpose, or etc.) will work for some people, but not others. Depending on how the camera is held during recording, the rotation necessary could be 90, 180, or even 270 degrees. Without reading the metadata, you're just guessing at how much rotation is necessary and the change that fixes one video will fail for another.

FFMPEG changed the default behavior to auto rotate video sources with rotation metadata in 2015. This was released as v2.7.

If your ffmpeg version is v2.7 or newer, but your rotation metadata isn't respected, the problem is likely that you are using custom rotation based on metadata. This will cause the same logic to be applied twice, changing or cancelling out the rotation.

In addition to removing your custom rotation (recommended), there's an option to turn off auto rotation with -noautorotate.

ffmpeg -noautorotate -i input.mp4...

This will also work in some older releases.

Depending on which version of ffmpeg you have and how it's compiled, one of the following should work...

ffmpeg -vf "transpose=1" -i input.mov output.mp4

...or...

ffmpeg -vfilters "rotate=90" -i input.mov output.mp4

What you can also do is remove the QuickTime specific metadata when rotate the .mov. This will make sure that the video is rotated the same way in VLC and QuickTime

ffmpeg -i in.mov -vf "transpose=1" -metadata:s:v:0 rotate=0 out.mov

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Here's the documentation on the -metadata option (from http://ffmpeg.org/ffmpeg.html):

-metadata[:metadata_specifier] key=value (output,per-metadata)

Set a metadata key/value pair.

An optional metadata_specifier may be given to set metadata on streams or chapters. See -map_metadata documentation for details.

This option overrides metadata set with -map_metadata. It is also possible to delete metadata by using an empty value.

For example, for setting the title in the output file:

 ffmpeg -i in.avi -metadata title="my title" out.flv 

To set the language of the first audio stream:

 ffmpeg -i INPUT -metadata:s:a:1 language=eng OUTPUT