camera How Samsung fixed slow motion and then ruined it again.

[Ertio]

TLDR: From 2015 to roughly 2019, Samsung smartphones encoded slow motion videos as real-time videos with the original frame rate and audio. Sadly, Samsung changed back to slowed-down video files.

 

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There are two ways smartphones record videos with 120fps or above.

 

The superior way is to encode the file with the same frame rate that was captured from the image sensor. The inferior way is to slow down the resulting video file. This means playback at normal speed means the content of the video is at a quarter or an eigth of real-time speed.

 

History

 

Samsung first added slow motion recording in 2009 to their Omnia II smartphone, then, after a three-year gap, again to their Note II from 2012. Until 2014, Samsung phones slowed down the resulting video files and did not record audio.

 

Apple first added slow motion recording on the iPhone 5s in 2013. But it recorded with sound and saved the file at original speed. A pre-installed video editor let the user manually choose slowed-down portions and export them to a new video file. Samsung did the exact same thing starting on the S6 in 2015, and all was good.

 

But a few years later, likely in 2019, Samsung changed back to the inferior behaviour of slowing down the resulting video file. At least, those files feature pitched-down audio, compared to no audio until 2014.

 

I get that slowed-down video files have one benefit: You get a slow-motion effect on video players that do not feature a speed selector. But that's it. But you might want to edit the video or watch it in real-time with sound too.

 

Real-time playback

 

Now that smartphones commonly feature 120 Hz screens, 120fps videos recorded on the Galaxy S6 from 2015 can be played back in real-time with the full smooth frame rate. Those recorded on the S5? Not so much. You could speed up to 4x or 8x speed (depending on the setting at the time of recording), but you would still have no audio.

 

Video editing

 

A slowed-down file is also bad for video editing on a desktop/laptop computer. Each time you want to change the speed, you have to make a calculation, by multipling the speed of the source file from the smartphone by x4 or x8 or by whichever factor in order to match real-time speed. This means if you want a portion of the video to be seen at half the real-time speed and the source file from the smartphone is encoded at 1/8 of the speed, you need to set the speed of this clip in the video editor to x4. Confusing, I know.