Blackmagic Decklink: dropping frames when using two capture streams

Graphics / Linux Linux
1

Hello all,

I have frame drops when trying to capture video from 2 Blackmagic Decklink cards, simultaneously.

Hardware config:

  • Tyan motherboard
  • 4 x Quadro K5000
  • 2 x Blackmagic Decklink 3D
  • 5x3 wall of Samsung TV screens

Software:

  • CentosOS 6
  • NVidia driver, provided/compiled by ElRepo, configured with SLI Mosaic
  • bmdtools for video capture

Symptoms:

  • one stream running well
  • two streams dropping frames and flickering (switch between signal and no signal several times per second)
  • two streams over ssh running well (displaying on another Linux system).
  • problem manifests also when using just one K5000 card with 4 screens, in default configuration (as generated by nvidia-xconfig)

Many thanks for your attention.

Suggestions, ideas, etc. much appreciated.

Cheers,
H.

2

Can you share the cmd line , by which you are running . {ffmpeg cmd line}
./ffmpeg -y -hwaccel cuvid -c:v h264_cuvid -i Despicable3.mp4 -map 0 -vf scale_cuda=1280:720 -c:v h264_nvenc -profile:v main -level 4.0 -preset fast -r 29.969999 -force_key_frames “expr:gte(t,n_forced*0.500000)” -f mpegts -muxrate 3000k -flags +ildct+ilme -top 1 -ac 2 -ar 48000 -c:a libfdk_aac -b:a 96k out.ts