[randomf]

I've been wondering for a while and can't find an answer to this:

SD to USB adapters exist, but is it possible to hook up an SD-to-USB cable and have a driver present a virtual sd disk to the camera but write the video directly to your computer RAM via USB?

That would solve the problem for all dSLRs.

[pdpi]

That seems pretty roundabout, when you have solutions like the Elgato CamLink that just takes an HDMI input from your camera and shows up as a completely standard USB Video Class device to the OS.

[randomf]

Many models don't give you "clean" HDMI output. It's usually low-res with overlay junk.

edit: if the elgato can do it with HDMI, the question remains can it be done directly with SD out?

e2: also, SD card readers/adapters are cheap and plentiful, this seems like it should be easier to implement

[calessian]

My DSLR camera has a mini HDMI out that you can use out of the box, doesn't require the camera to be in recording mode or such. It simply gives you the live video feed -- rather than having it write to SD card, having software on your computer decode the video & show the last frame there.

The only option I think (it's been a while) I had to vaguely enable is to have it not show the normal camera UI over HDMI, but that was a simple setting.

Having hardware emulate a SD card sounds like a niche product, if anything, whereas the only item I needed for my camera was a mini-HDMI to HDMI cable.

[pdpi]

The elgato is doing something completely straightforward — video output to video input, done. With only a few details, it’s almost like a regular webcam where the controller is in the usb plug rather than the webcam’s body.

The SD thing has all sorts of nastiness to it.

First, you won’t have a standard usb video input, so you’re going to need to do a bunch of awkward driver work to get applications to consume the video feed.

Second, you’ll have to deal with the lag and jittery video that you get because the camera will almost certainly buffer writes.

Then you have to figure out how to get the controller in the SD reader to understand the incoming writes, which it was most certainly not designed to do.

[progbits]

SD card writes are buffered, this will presumably have too high latency for streaming.

[kalleboo]

Wi-Fi-enabled SD cards that automatically inspect the filesystem and upload your photos to the internet or a computer already exist, it shouldn't be impossible to modify the firmware to upload MP4 files in a streaming fashion, assuming they have the bandwidth.

[numpad0]

SD interface is a bit complicated to set up for average hackers, on top of buffering issues. Likewise there are some cameras with PCIe derived interfaces for memory cards, but those aren’t actively being hacked either.