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Comment by Jack000 | Hacker News Reader

amazing camera. Would have been perfect if it had 10bit log like the GH5 though.

Or even raw. I'm surprised so few cameras offer raw video support, but they all have it for the photos.

Could it be a bandwidth issue? I remember reading about 120fps 4k video on an Android phone being limited to only a few (real-time) seconds because there wasn't enough I/O bandwidth to stream the video to storage so it had to stream into a specialized hardware buffer that was relatively small and expensive.

Definitely a lot of bandwidth required. 60 fps 4k would be 1.7 GiB/sec, 120 fps twice that.

3840×2160×10×3×60÷8÷1024÷1024÷1024

RAW format doesn't just mean an uncompressed image like a PNG. It's a direct readout from the sensor with minimal processing. It can be substantially larger than you'd expect just based on the resolution * bits per pixel.

You are correct, but don't forget the Bayer encoding that makes things smaller!

Good point! But in the other direction, don't forget that even those there's less "pixels" than expected from the sensor, there will be more than 10 bits per channel, typically 12 or 14. I shouldn't have said it's larger, not necessarily - but it's definitely not 1:1!

You don't need a x3 there since most cameras use a single monochrome sensor with a colour filter array on top – the debayering process can happen offline.

Modern SD cards go up to 300 MB/s for writes. That should be enough. Even if you dump the pixel data with zero compression.

8-bit pixels: 1920x1080x30 = 62.2 MB/sec

14-bit: 109 MB/s

Even UHD in 8 bits should work.

I think if you're Raw spatialy down-sampled you'll want RGB and not Bayer under-sampled so triple that. No SD is reasonably over 250MB/sec and they are all 64GB. Even at FHD 30Hz you'll only get 30sec of 8bit (not really Raw) video on your insane SD card.

https://havecamerawilltravel.com/photographer/fastest-sd-car...

No, that makes no sense. Why would you store debayered data when you can store the original with the same exact results?

You realize that Bayer data counts every column and row whether R G or B, right? Half the pixels (21Mpix) are green and the other 2 quarters are R and G.

So if you're going down to FHD (2kx1k) from 42Mpix (8kx5k) you have already lost massive ammounts of resolution (and noise). Bayer FHD would be SPR (sup-pixel rendered) and even lower resolution (1/3 RGB e.g. 1080 lines of 1920 RG/BG alternating columns) than most JPEG FHD (natural scene) not suitable for video compression much less Raw. That would be silly.

If you don't down-sample the data somehow you can't even get it off the CIS which are limited to ~2-5Gb/sec. Since most reasonable image sizes are large enough you can see color at full resolution we typically use RGB at FHD, compressed or not. Alternately, you can go to 4:4:4 to 4:2:2 or even 4:1:1 in Yuv (YCbCr), but that's not Raw or anything like it.

Because it's literally another magnitude of data rate. For cinema raw, the whole camera has to be designed around a high speed data path to a very fast and wide storage system. This is much bigger, more power hungry, more thermally demanding, and more expensive than even the high end DSLRs.

The a7iii can shoot JPEG at 10fps pretty much continuously as far as I can tell. Well, that's about 80MB/s. Cinema RAW 4K @30fps varies wildly but one number I've heard is about 4.5Gbps. 550MB/s. That is a substantial increase which would require not only a redesign of the entire data path but presumably much higher grades of storage. Maybe one day but not happening anytime soon!

Many cameras shoot raw video - blackmagic, RED, kinefinity.

And even more (Sony FS, Panasonic EVA 1) with external recorders.

Almost all use SSD though for raw video - new SD cards have good enough speed but haven't been widely implemented - https://liliputing.com/2018/02/wd-demos-sd-card-880mb-s-spee...

And the data rates for raw video aren't that high btw - redcode is lossless at 3:1 and visually lossless up to 9:1. CinemaDNG is about 3:1 - 4:1 (vbr).

My blackmagic pocket shoots 1080p/30fps RAW on a 90MB/s SD card and the camera is the size of smallest mirrorless.

I think the real reason we haven't seen more consumer RAW video is there isn't enough demand - which is a shame.

While I personally love RAW video for grading I'm looking forward to seeing how much dynamic range gets stored in 10bit HVEC footage, which I think will become very popular (because of HDR displays)

Even the article you linked says the new SD cards only do 430MB/s in testing - I'm afraid a full SSD is the only way to go for raw video.

New UHS-ii cards do up to 300MB/s sequential write, blackmagic can record 1080p raw on them, could probably push more. For 4k Check BM Ursa Mini pro and Canon C200 - both shoot 4k raw internally to Cfast cards

How many seconds would you like?

For true Raw it would be 40Mpix×10bitx60Hz. That's 3GB/sec which greatly exceeds the imager transport speed. Even 4k@30Hz 10bit RGB Raw would be ~900MB/sec depending on how they down-sample Bayer, which is several times the imager transport limit (2-5Gb?). Even the highest speed SD cards can barely do 100MB/sec write speeds (edit: some can now do 250MB/sec but they are only 64GB) so you would need a DDR-DRAM buffer for as much as you wanted to store. 32GB would give you ~30sec burst, and you could get 4 bursts separated by 5min on a 128GB card, but your battery wouldn't last long.

Really high dynamic range M-JPEG would be reasonable unless you're trying to resolve the noise in your CIS.

A decent number of prosumer cameras allow you to record raw video via HDMI, to an external recorder with a proper hard drive.

Though often at lower resolutions/fps/color than the SD/CF, so maybe there's a bandwidth limitation there too?

I think there's also some "antifeatures" involved; artificially limiting that ability on cameras that cost less than $5k to avoid disrupting the expensive "cinema video camera" market. Of course custom firmware can sometimes help with that.

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