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android-emulatorscreen-recording

screenrecord not working in emulator

Since 4.4 KitKat, Android has a shell utility screenrecord to record the Android device screen.

If I connect a physical device with the adb utility over USB, I can do the following:

adb shell screenrecord /sdcard/sample.mp4
adb pull /sdcard/sample.mp4

But if I do the above for an Android emulator, I will get an empty sample.mp4 file.

adb shell screenrecord /sdcard/sample.mp4
adb shell ls -l /sdcard/sample.mp4
-rw-rw---- root     sdcard_r        0 2016-06-18 05:37 sample.mp4

If I execute screenrecord directly in a root console in emulator, I see the following:

root@flo:/system/bin # ./screenrecord /sdcard/sample.mp4                       
[1] + Stopped (signal)     ./screenrecord /sdcard/sample.mp4 
root@flo:/system/bin # 
[1] + Illegal instruction  ./screenrecord /sdcard/sample.mp4

Why does screenrecord not work for emulator?

Solution

  • Screenrecord uses MediaCodec API. https://developer.android.com/reference/android/media/MediaCodec.html

    To be precise, Screenrecord directly calls the native interface of MediaCodec.

    To the best of my knowledge, no emulator supports MediaCodec yet. They all support higher level interface MediaPlayer https://developer.android.com/reference/android/media/MediaPlayer.html.