Compressor - video converter for mov, mp4, webm and mkv

An interface for ffmpeg that converts, compresses and remuxes videos


This shortcut is an interface for ffmpeg video conversions. The free a-Shell mini app is required because it provides ffmpeg and ffprobe.

The shortcut was made using iOS 16 and 16.1.


  1. Run the Compressor shortcut directly or from the share sheet
  2. Choose video options
  3. Start the job


  • Dramatically compress file size (700MB 4K = 50MB 720p)
  • Convert from MOV, MP4, MKV & WEBM files
  • Video options: width, height, format, codec, bit rate, fps
  • Audio options: codec, bit rate, sample rate
  • Preserve HDR and GPS location metadata if possible
  • Remuxing MKV files to MP4 is super fast
  • Support for video shot in Cinematic format

Compressor Promo 1


  • a-Shell mini app
  • a video to be converted
  • a little knowledge about video encoding helps


Because this shortcut is an interface for ffmpeg, it may interact with a-Shell mini nearly 30 distinct times. This means you can expect 20+ prompts for permissions the first time you use this shortcut.

The shortcut will ask for permissions...

  • to use the a-Shell mini app (20+ times)
  • to access files and folders (4-5 times)
  • to run Shortcuts (2 times)
  • to access Photos (2-3 times)

Compressor Promo 2

Encoder Settings

  • Output Video Name - Change file extension to change format.
  • video_codec - Usually hevc, h264 or copy
  • video_width - Width in pixels. -1 for scaled.
  • video_height - Height in pixels. -1 for scaled.
  • video_fps - Video speed in frames per second
  • video_bit_rate - Video bit rate in M/s
  • audio_codec - Usually aac
  • audio_bit_rate - Audio bit rate in k/s
  • audio_sample_rate - Usually 44100 or 48000

Minimum Bit Rates

Here are the suggested minimum bit rates at 30 fps.

Resolution Min. Bit Rate
720p 1.5 M/s
1080p 3 M/s
4K 6 M/s

Remuxing MKV to MP4

Use the fast "copy" codec with MKV files to remux to MP4 without any loss in video quality.

When using the video "copy" codec, all other video encoder values (width, height, fps, bit rate) should be set to "auto." Set the audio codec to "aac" for maximum compatibility.

HDR Compatibility

Choose the "hevc" codec (or "copy") to preserve HDR. Videos with HDR will be converted (tone mapped) to SDR when using the "h264" codec.

GPS Metadata

The shortcut will try to preserve any GPS location metadata during conversions.

Default Encoder Values

The default encoder settings can be changed by editing the "DefaultSettings" dictionary in the shortcut. The default video encoder settings are currently 720p, hevc, auto fps, 1.5M/s. Audio defaults to aac, 128k, 44100.

Advanced Options

Tap on "Start Job (advanced)" to edit the ffmpeg command before it is executed. Add filters and make other changes. Check the ffmpeg documentation for more information.

Known Issues

  • Encoding speed varies by device. Older devices may perform poorly.
  • a-Shell mini can't encode in the background.
  • a-Shell mini incorrectly reports "No space left on device" errors on some devices.
  • WEBM metadata is wrong or missing.
  • Some files cause the shortcut to crash while reading metadata
  • The AV1 codec is not supported
  • Cinematic video conversions lose GPS metadata


  • Try jobs at least twice before giving up.
  • If a job fails, check a-Shell mini for error messages.
  • Force close a-Shell Mini if it hangs or shows a large number of error messages.
  • Try restarting device if a-Shell mini reports out of space error.
  • The shortcut saves your session settings to make restarting jobs easier.
  • If the shortcut fails from the share sheet, try running the shortcut directly.
  • If the shortcut fails, try disabling metadata analysis for that file.

Latest Release Notes

0.1.8 - Nov. 10, 2022, 3:45 a.m.

The default audio sample rate changed from 44100 to auto. The default audio rate changed from 128k to 192k.

Version history