How to capture HDMI video from PC with Cam Link 4K & FFMPEG

AMD Settings

• Enable GPU Scaling on 1920x1200 Display 1 (if you have one, this will make both 1080p)
• Pixel Format: YCbCr 4:2:2 on Display 2 (Cam Link 4K)
• Disable HDMI Link Assurance on Display 2 (just in case)

Windows Settings

• Clone Displays (1080p)

Hardware

• Directly plug in the cam link into your usb port, do not use cable (if you have 10Gbps or faster ports use that)

Capture (FFMPEG, AMF)

720p AVC

• ffmpeg -hide_banner -rtbufsize 1024M -f dshow -i video="Cam Link 4K":audio="Digital Audio Interface (Cam Link 4K)" -vf scale=1280:-1 -pix_fmt yuv420p -c:v h264_amf -b:v 50M -c:a flac -preset:v high -f matroska test.mkv

720p HEVC

• ffmpeg -hide_banner -rtbufsize 1024M -f dshow -i video="Cam Link 4K":audio="Digital Audio Interface (Cam Link 4K)" -vf scale=1280:-1 -pix_fmt yuv420p -c:v hevc_amf -b:v 50M -c:a flac -preset:v high -f matroska test.mkv

1080p AVC

• ffmpeg -hide_banner -rtbufsize 1024M -f dshow -i video="Cam Link 4K":audio="Digital Audio Interface (Cam Link 4K)" -pix_fmt yuv420p -c:v h264_amf -b:v 50M -c:a flac -profile:v high -f matroska test.mkv

1080p HEVC

• ffmpeg -hide_banner -rtbufsize 1024M -f dshow -i video="Cam Link 4K":audio="Digital Audio Interface (Cam Link 4K)" -pix_fmt yuv420p -c:v hevc_amf -b:v 50M -c:a flac -profile:v high -f matroska test.mkv

OBS Studio

• You can now simply use it as usual in obs studio

Reference

• switch to h264_nvenc or h264_qsv if you have nvidia or intel gpu
• ffmpeg -hide_banner -list_devices true -f dshow -i dummy
• if you are using a DSLR, try switching camera to 720p60 mode, also change the pixel format if it has support for that to YCbCr 4:2:2 or YCbCr 4:2:0 to lower the bandwith used