2x slowdowns in FFMPEG recording for the scrcpy server

[JijaProGamer]

• OS: Windows 11
• Scrcpy version: 3.1
• Installation method: Windows release
• Device model: Default BlueStacks 5
• Android version: 9

I'm pushing the scrcpy server using the usual method:

adb push scrcpy-server-v3.1 /data/local/tmp/vlc-scrcpy-server.jar
adb forward tcp:6751 localabstract:scrcpy
adb shell CLASSPATH=/data/local/tmp/vlc-scrcpy-server.jar
app_process / com.genymobile.scrcpy.Server 3.1
tunnel_forward=true control=false cleanup=false
max_size=1920 raw_video_stream=true \

However, when trying to record it to file using:

ffmpeg -re -i tcp://localhost:6751 -f h264 test.mkv

It outputs:

frame= 272 fps= 53 q=28.0 size= 2304KiB time=00:00:10.80 bitrate=1747.6kbits/s speed= 2.1x

Meaning that it is 2.1x in slow motion. How would I bring it to 1x?

[JijaProGamer]

In conclusion:

Slowmotion 1:
ffmpeg -i tcp://localhost:6751 test.mkv -y

Slowmotion 2:
ffmpeg -re -i tcp://localhost:6751 test.mkv -y

Fast forward (1.25x-2x, depends on CPU, -r 50 being double the fps):
ffmpeg -r 50 -i tcp://localhost:6751 -r 50 test.mkv -y

Seemingly good real time speed, but I'm not sure if it actually is real time or just another trick by luck:
ffmpeg -r 50 -i tcp://localhost:6751 test.mkv -y

Having it -r 50 (so doubling the input framerate) is very worrying in my opinion, so I belive there is another issue here.

EDIT: After further tests, it seems like the "ffmpeg -r 50 -i tcp://localhost:6751 test.mkv -y" method is fast forward too.

[yume-chan]

See #5742 (comment) and #5742 (comment)