Improve orientation support

[rom1v]

Problems

There are currently two options to rotate the video:

• --lock-video-orientation: it rotates the capture, but does not work for camera capture, and does not work at all for Android 14+ (Android 14 beta lock orientation doesn't work as expected when the device goes into landscape mode. #4011)
• --rotation: it only rotates the display, so the rotation is not applied to a file recorded with --record
• (less important) there was no way to support flipping the video (Screen Mirrored is Inverted #1380, Add Command-Line-Option to flip horizontal (Feature Request) #3819)

As a consequence, in particular, it was not possible to record a vertical video from a camera capture.

Changes

New orientation option

Introduce a new option --orientation (and separate options --display-orientation and --record-orientation if needed) which supports the 8 possible orientations (4 rotations × 2 flips):

scrcpy --orientation=0
scrcpy --orientation=90       # 90° clockwise
scrcpy --orientation=180      # 180°
scrcpy --orientation=270      # 270° clockwise
scrcpy --orientation=flip0    # hflip
scrcpy --orientation=flip90   # hflip + 90° clockwise
scrcpy --orientation=flip180  # vflip (hflip + 180°)
scrcpy --orientation=flip270  # hflip + 270°

The rotation is expressed in degrees clockwise so that --orientation=90 works for vertical video from a camera (it's more natural than --orientation=270 or --orientation=-90).

It is possible to change the display orientation dynamically using shortcuts:

• rotate display left: MOD+←
• rotate display right: MOD+→
• flip display horizontally: MOD+Shift+← or MOD+Shift+→
• flip display vertically: MOD+Shift+↑ or MOD+Shift+↓

The rotation is applied to a recorded file by writing a display transformation to the MP4 or MKV target file.
Flipping is not supported for recording, so only the 4 first values are allowed when recording.

For MKV files, unfortunately, some players currently do not handle it properly:

• I proposed a fix for VLC
• I reported an issue for MPV

MP4 files are correctly handled by these 2 players (and remuxing an MKV file to an MP4 file also fixes the issue).

--rotation is now deprecated.

Locked video orientation adaptation

For consistency, --lock-video-orientation has been adapted to express the value as a number of degrees clockwise, and the values 1, 2 and 3 are deprecated:

• --lock-video-orientation=0 → unchanged
• --lock-video-orientation=1 → --lock-video-orientation=270 (now, it's clockwise!)
• --lock-video-orientation=2 → --lock-video-orientation=180
• --lock-video-orientation=3 → --lock-video-orientation=90 (now, it's clockwise!)

Result

Now, it is possible to capture and record a rotated video from the camera:

scrcpy --video-source=camera --camera-size=1920x1080 --orientation=90 --record=vertical.mp4

Binary

Please review and test.

Here is a binary for Windows:

• scrcpy-orientation.zip _{SHA-256: 398e51af33be62263c5190e8b69fbfbdcbceae2ca782b0bd431efc5157451825}

[rp1231]

Works fine for me but I get a lot of audio feedback when using this option on my pc speakers:
scrcpy --video-source=camera --camera-size=1920x1080 --orientation=90
Any way to mitigate this issue?

Also does this mean that it's possible to use the phone as a webcam on windows as well?

[rom1v]

Works fine for me but I get a lot of audio feedback when using this option on my pc speakers

You can disable audio capture (--no-audio), you won't get any audio at all.
Or you can disable audio playback (--no-audio-playback), the audio will still be captured and recorded, but not played.

Also does this mean that it's possible to use the phone as a webcam on windows as well?

You can display the webcam in a window, then you can probably capture it with OBS and expose it as a webcam on Windows (apparently this is what Mishaal Rahman did for his recent article, but I have never tested).

[rom1v]

A new option --v4l2-orientation should also be added (and automatically set with --orientation) to orient a v4l2 video stream.

However, just setting a display matrix does not work, we must create and apply an AVFilter "transpose". Is someone interested in adding this feature for v4l2? (The FFmpeg sample decode_filter_video.c might help)