Hi,
I haven’t found anything about this topic here so I hope it’s not an old discussion. I’m using a Jetson Nano board to record the video and sensor data from a ZED 2i and store it on a sd card. The calculation of depth shall be done afterwards with a high performance pc.
So the only task of the Jetson is recording. We have enough space on the sd card, but we don’t have much computing power. So it would be nice if the recording was not compressed.
But I can’t find any information about the recording of uncompressed .svo files. There is the option to record lossless, sure, but that needs a high cpu load and the very fast H265 compression doesn’t produce a lossless record. So is there any option in the API like COMPRESSION_MODE::NONE ?
Thanks in advance!
Hi
Unfortunately, this is was possible on very old versions but was dropped.
The disk bandwidth requirements were just too high and the SVO files were too big to be usable. Since this was uncompressed, the data bandwidth is equivalent to the USB 3.0 (5 Gbit/s), resulting in many dropped frames during recording and SVO files so huge it would significantly shorten the possible recording length.
However, we’re working on a new mode that would be almost lossless and would use the hardware encoding capabilities, resulting in no quality loss, very low hardware load, and still smaller SVO files.
Ok, thanks for the fast reply. The new mode sounce pretty good but I guess it won’t be availabe within the next weeks, right?
What I don’t understand is how can the lossless mode write the .svo file with about 50 MB/s (correct me if I’m wrong, just an estimation) if the compression ratio is 2:1 and the data bandwidth of the camera is 5 GBit/s → ~ 625 MB/s.
Also which version of the SDK had the uncompressed mode and was it compatible with the ZED 2? I’m just curious how the results would be compared to the current modes.
Yes, the new mode won’t be available until Q1 2022.
The bandwidth is indeed not really as high as full USB3.0, the actual would be something like this:
- At 1080p, 30fps, side by side images, YUV422:
1920*1080 * 2 * 30 * 2 bytes / sec, so ~ 249 MB/s
That’s doable on an SSD but I don’t think (micro) SD cards are fast enough. Even with good SATA SSD we had frame drops regularly.
At the time the ZED SDK didn’t support the ZED2, it may have been in the ZED SDK 1.2.