Hi there. I'm just equipping myself for wireless astro photography and was pointed at Indi, which is exactly what I was looking for. I will shortly have a Nexstar Evolution 8" telescope, a ZWO ASI120MC camera and was planning to use a Raspberry Pi as the controller at the telescope running Indi, powered from the Nexstar evolution's USB interface, and a Wifi interface to a PC running Ekos in a nice warm house .

One worry I have, though, is speed of access to storage. I've been told that 50 to 70 MB/s might be required to run 640 x 480 video at 50 fps. The SD card I have chosen will do 10 MB/s writes when it is in the Pi and I can see that the fastest SD card on the Pi could do 20 MB/s writes. I could use an external USB HDD but this article suggests that it won't be much faster, especially since the camera feed will come over USB also. The other alternative would be to switch to a Banana Pro board, or similar, which has an on-board SATA interface.

So, my questions are:

1. Should I worry about transfer speed for image storage?
2. If so, can anyone recommend a Pi-like board with an on-board SATA interface, preferably one that Indi has been used with?

Rob

Rob,

I highly recommend the Odroid-C1 board with an eMMc card, running Ubuntu. You'll get all the updated Indi stuff over the PPA.
The speed of the above kit VS a Raspberry PI is like upgrading your hard drive in your laptop to an SSD drive.....

I do have 3 different Pi. Model A, B and B+.

Hi there, by a curious coincidence I just spotted your comment on the Ekos YouTube video here .

Anyway, very interesting. I just had a look at the Mikronaut's benchmarks here:

www.mikronauts.com/hardkernel/odroid-c1-review/6/

For Odroid C1 the write speed gets up to 23.1 MB/s but the comparison table suggests that the Imagination CI20 is even better at 32.9 MB/s. However that's for the eMMC NAND Flash of which there is only 8 Gigabytes mounted on the board. Do you think that would be enough? Might I be better going for the SATA option? Too many choices.

You will not be able to stream 50 frames per second using INDI! INDI is actually slow when it comes to video streaming since for _each_ frame, it encodes the data to base64, sends the data, it is received and then decoded from base64 to raw image and THEN it gets displayed. For high frame rates also, the camera and driver will be generating frames faster than it can send them to the client, resulting in the video stream being out of sync and eventually INDI server will stop due to a large queue of unsent frames.

Therefore, you'd have to experiment with a usable frame rate. For guiding purposes, you don't need anything faster than 1 frame per second. For recording video, I think it can be done at the client side without sending the frames back to the client.

That's understood, I was assuming that all the video would be stored locally on the Raspberry Pi or equivalent. Does the Indi/device interface for cameras already support that (thinking something like a camera control interface via Indi but with data stored locally to file on the Pi that can be locally processed on the Pi and then the finished product retrieved via Indi) or do I need to develop my own interface for that?

Rob

Well, INDI V4L2 driver can store ".ser" files locally, but I haven't found an .ser player yet on Linux to test that out. If that works OK, it can be extended to ASI and other cameras.

Interesting. A Google search suggests that a .ser file is a generic java container for a binary object. Is that correct (not sure how Java got into this)? If so, how to read it would likely depend what the driver had stuffed into it. Maybe I'll have to wait until I have something I can poke at before I can resolve this any further.

SER is a video format that can be opened with programs such as Registax.

Ah, thanks for that. I see Registax is Windows but runs under Wine on Linux. Not sure the Pi is up to that but at least it's proof that there are Things Out There to allow me to progress.

Banana Pro with SATA is the optimum solution I think - you get storage as much as you can afford (with price lower than for eMMC) and high speeds. PPA will work also (Odroid and Banana both support Ubuntu). About SER... I tried it once - something is not working right. I don't remember very well the details but I couldn't work with the SER file I recorded. Siril for example said that something is wrong with indexing. In order not to mislead I will test again!

Just tried with Siril and SER loads fine.

Yeah, verified it with my home web-camera, also fine. Have to check DMK at work... One thing noticed - color stream make my processor run crazy on all cores. Is it ok?

One proposal - make it possible to preview while record is on. Also make it possible to lower preview fps (In order to be able to preview from remote machine). This will help to make one step forward to KStars being acceptable for planetary recording