[Wear OS General] bernarbernuli:
How to Record the watch screen (ScreenCast)

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In Wear OS it is possible to record in video everything that happens on the watch screen, without installing third-party applications, you just need to connect the watch via Wifi to a PC and use the command "screenrecord" of adb. It is a very useful tool to show in a clear way, for example an error that is occurring on your watch, instead of a simple screenshot.

If you haven't done it yet, follow the steps in the "Prepare watch for advanced features" section of the first post (Install ADB tools on the PC and enable debugging via WIFI in developer options on the watch).

On the computer, open a command window, for this in Windows type "cmd" in the start bar.

Then enter the following command to connect to the watch. Then accept a message on the watch that allows the computer to connect.

adb connect Watch_IP:5555

Execute the following command, it will start recording in video everything displayed on the watch screen. To stop recording press Control + C keys from the command line. The resulting video is saved in the watch itself in a raw format file, i.e. unprocessed and therefore with a very large size depending on the seconds you have recorded.

adb shell screenrecord --size 454x454 --o raw-frames /sdcard/screencast.raw

Once you have captured the video, you must move it to your PC for further processing with the following commands. The first one to copy the raw video to the PC and the second command to remove it from the internal memory of the watch.

adb pull /sdcard/screencast.raw
adb shell rm -f /sdcard/screencast.raw

Finally, you need to convert the raw video file that is in raw format into a video that most video players can understand, for that type the following command to convert the raw file to mp4 with the help of the ffmpeg tool.

ffmpeg -f rawvideo -vcodec rawvideo -s 454x454 -nostats -loglevel 0 -pix_fmt rgb24 -r 10 -i screencast.raw -an -c:v libx264 -pix_fmt yuv420p screencast.mp4

Considerations:

I have generated a batch file that facilitates the process of recording the screen, copying the RAW file to the PC and converting it to MP4 format for those who want to get complicated with ADB commands. The batch file is only valid for Windows environment. You can download it from here, unzip the files in a folder, along with the BAT file is included ADB Tools and ffmpeg that are necessary for the tool to work.

If you want to record when and where you are tapping the screen during a screencast you have to enable "Show taps" in Settings > Developer Options. This option will circle the areas you are tapping with your finger on the screen, which is very handy for screencasts.

Video is recorded without sound.

The video is recorded on the watch in raw format, once on the PC the raw file can be converted to mp4. The raw files allow to obtain an image without any compression, as a consequence, the size of the .RAW files is very large, for example, 3 minutes of recording will occupy in raw format almost 1 Gigabyte (when converted to mp4 it will occupy only 2 Megabytes).

When recording, it continues until you press Ctrl + C or in theory until the time limit is reached (3 minutes) and then it would stop automatically, however I have observed that it continues recording beyond 3 minutes (even if you set it in the parameters of the command "adb shell screenrecord"), I guess the limit is in the free space in the storage memory, which taking into account the size of the raw files will occupy very fast.

Another alternative to make recordings of the watch screen, is from the phone with Bugjaeger app (instead of the PC) however it is an option limited to the paid version of the app.

Some time ago, it was leaked that Google is going to include the option to record watch screen in the Wear OS app on the phone, but it is not yet available.

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