Raspberry Pi DTE recorder and HDMI converter

[Richard Aspden]

Hi there,

I have been working on building an DTE recorder using a Raspberry Pi Compute Module. This works by attaching a PCI-E Firewire card and using dvgrab to capture from the camera. It needed a custom kernel to enable Firewire and the software needs a bit of work but by piping the output from dvgrab I was able to send the video to FFPLAY for a preview and display timecode and record status since FFPLAY supports overlaid text. This is all working well. The camera triggers the recording and the recordings are great from DV and HDV, but in truth the delay on the preview is such as to make not so useful.

However it got me thinking. I have a lot of DV and HDV cameras but I don't have a way to convert Firewire to HDMI and the various devices that do this to SDI at least, from Canopus, Miranda and Roland, are either very scarce or prohibitively expensive. However if I can output from DV grab in fullscreen (as I do with the DTE) I can use the HDMI output from the PI to view on the TV (capture device) and effectively I have a crude but effective HDV to HDMI device. So I made a stripped down version of the DTE project and tested it. The delay is no longer an issue really since this will mainly be for playback, but it was then I noticed the preview had a very poor FPS - around 10-15 I reckon. I'm guessing this is just due to the limitations of the Pi. I did try piping to other outputs (VLC and Mplayer) but the results are identical.

I could try the new RPI 5. I have a PCI-E hat for this so it would be easy to try. However I'm thinking that perhaps arm is not the way to go and that to be able to do this I'd need an x86 based machine. The x86 SBCs are quite expensive but I was wondering if perhaps the ASROCK N100DC-ITX might do the trick. I therefore have two queries I would appreciate the help of people here with.

1) Not being an expert on how processing speeds compare these days, do you think the ASROCK N100DC-ITX would offer a fast enough improvement to output 1080p @ 50fps video playback from the Firewire source?

2) Before I go an blow a load of cash on this, is there anything I can try with the current setup to get a better performance? I was wondering about encoding to specific codecs before output, or perhaps the GPU is being bypassed in favour of software based video output - how to check this on the RPI (Bullseye OS).

Thanks in advance for your help.

[Andrew Smith]

"prohibitively expensive" ... welcome to our world. :-)

I'm just pretty darned impressed at what you've been able to do with a Raspberry Pi.

Andrew