SSD Recorder 4.6K RAW 60P

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Tomriechart

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SSD Recorder 4.6K RAW 60P

PostMon Feb 19, 2018 11:29 am

Hi, I'm buying the URSA MINI PRO in the next few days and I have some questions about the recorder.

1. One of the important things to me is recording in 4.6K RAW 60P, now the question is there such thing as any SSD that can hold it or the maximum of the recorder is 30P in this quality?

2. Can I do dual record SSD and CFAST together to get a 4.6K RAW 60P recording?

3. Is it possible to record on 4K RAW 60P rather than 4.6K with SSD?

4.Last question about the SAMSUNG 850 PRO:

If the maximum megabyte per second of the camera in this quality is 513 MBPS and the SSD can work on the writing of 520 MBPS it should work not?


Thank you
Tom Riechart
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Tim Schumann

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Re: SSD RECORDER 4.6K RAW 60P

PostMon Feb 19, 2018 9:53 pm

Tomriechart wrote:1. One of the important things to me is recording in 4.6K RAW 60P, now the question is there such thing as any SSD that can hold it or the maximum of the recorder is 30P in this quality?

For 4.6k Lossless RAW you should be able to hold at just above 40fps on some of the faster SSD's like the 850 Pro. You will be able to hit 60fps Lossless at 4.6K for a short period of time, depending on the speed of your SSD this will vary. From memory you get about 15 seconds on the faster ones.

If you need 60 frames at sustained speeds then you will need to use compressed RAW which we offer in 3:1 and 4:1 or any of the ProRes 422 flavours.
2. Can I do dual record SSD and CFAST together to get a 4.6K RAW 60P recording?

Yes you can. So with a CFast from the certified RAW list and a SSD from the certified RAW list you will be able to shoot dual card and hold at 60fps with Lossless RAW until your cards are full.
3. Is it possible to record on 4K RAW 60P rather than 4.6K with SSD?

Yes you can window the sensor in a lot of different ways meaning your can record RAW at 4.6K 2.40:1, 4K 16:9, 4K DCI, Ultra HD, 3K Anamorphic, 2K 16:9, 2K DCI, 1920x1080.

If you are finishing with a 2.40:1 aspect ratio then shooting Lossless RAW at 4.6K 2.40:1 will get you much higher frame rates to a single card because the data rate is lower as you are not recording the information in the unused picture area.
4.Last question about the SAMSUNG 850 PRO:If the maximum megabyte per second of the camera in this quality is 513 MBPS and the SSD can work on the writing of 520 MBPS it should work not?
The claimed write speeds of SSD manufacturers are rarely the same as their sustained speeds writing video. There is more information about this on our certified SSD list.
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Tomriechart

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Re: SSD RECORDER 4.6K RAW 60P

PostMon Feb 19, 2018 10:06 pm

Thank you very much for the quick response!

And other questions:

When you say I'll have 15 seconds of recording, you mean after 15 seconds there will be a DROP FRAME?

How do I do the DUAL RECORD with SSD and CFAST, is it just an option in the settings I run?

How does the split between the two cards actually work? The clip split into two parts between the cards? How do you connect them?

And thank you again!

Tom Riechart
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Tim Schumann

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Re: SSD RECORDER 4.6K RAW 60P

PostMon Feb 19, 2018 10:59 pm

Yes after 15 seconds at 4.6K Lossless RAW 60p to a single card you will begin to drop frames. You can select an option in our menu that stops recording as soon as the card drops frames if you want so this is easy to test for and work out how long you will get.

When the SSD is connected it shows up by default as your second slot so all you need to do is mount media in the first CFast slot and the SSD recorder and then ensure that REC RAW ON 2 CARDS is switched to 'On'.

Our RAW files are recorded as a DNG stack where each frame is a single DNG file in a folder for each clip. There is also a WAV file recorded for audio to match. When you record in dual card mode it bounces between the two types of media to halve the data rate required. It records like a RAID 0 so you are recording odd frames to one slot and even frames to the other.

Then in post you simply merge all of the DNG's for each clip into a single folder along along with the WAV file and Resolve will see that as a single clip. It will then be seen as slow motion in your NLE unless you have shot it with a project frame rate of 60p.
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Tomriechart

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Re: SSD RECORDER 4.6K RAW 60P

PostTue Feb 20, 2018 7:39 pm

Another question:

If I buy an SSD that is faster than the SSD recommended on your site, can it hold 4.6K RAW 60P?

And is there a problem buying an SSD that is not recommended even though it is faster than recommended?


Thanks
Tom Riechart
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Tim Schumann

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Re: SSD RECORDER 4.6K RAW 60P

PostWed Feb 21, 2018 2:46 am

As we state on our list of recommended SSD's at the bottom....
Some SSDs can have up to 50% lower write speed than the manufacturer’s claimed speed. So even though the disk specifications claim an SSD has speeds fast enough to handle video, in reality the disk is not fast enough when used to store video data for real time capture.
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rick.lang

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SSD RECORDER 4.6K RAW 60P

PostWed Feb 21, 2018 6:38 pm

I believe BMD is still recording with 128KB blocksize. BMD tests sequential records to fill the media in a continuous single clip. Manufacturers tout high speeds but they’re seldom recoding to those specs except the few that actually test their wares on a BMD camera. Who ya gonna trust? Ghostbusters? A manufacturer? BMD!


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Robert Niessner

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Re: SSD RECORDER 4.6K RAW 60P

PostWed Feb 21, 2018 7:36 pm

Tomriechart wrote:Another question:

If I buy an SSD that is faster than the SSD recommended on your site, can it hold 4.6K RAW 60P?

And is there a problem buying an SSD that is not recommended even though it is faster than recommended?


The problem is that the SATA-3 standard of those SSDs has a theoretical limit of 6 Gbit/s which is 768 MB/s. Because taking 8b/10b encoding into account, the maximum uncoded transfer rate is 4.8 Gbit/s (600 MB/s). The practical write transfer speed ceiling for all SSDs seems to be around 540 MB/s.

The maximum framerate for full sensor RAW 4608 x 2592 is 60fps ~ 788.6 MB/s - that does not go well with SATA-3s speed.

3 factors influence data rate:
1. resolution
2. frame rate
3. compression

Uncompressed 12bit RAW 4608 x 2592 @ 30fps = 512.6 MB/s | @ 60fps = 1025.2 MB/s
Lossless (like ZIP) compressed RAW @ 30fps ~ 394.3 MB/s (compressibility depends on footage content)
Lossy 3:1 compressed @ 30fps = 170.9 MB/s | @ 60fps = 341.8 MB/s
Lossy 4:1 compressed @ 30fps = 128.15 MB/s | @ 60fps = 256.3 MB/s

Note A): All other RAW resultions are from a cropped sensor (windowed). 120fps is 2048 x 1152 or lower (windowed).

Note B): Do not mix up cards/SSDs maximum write speed with sustained write speed. The latter might be much lower, especially when the cards/SSDs get fuller.

The URSA Mini cameras always use at least lossless compressed RAW. It does not make sense to use completely uncompressed RAW - that is just a waste of bandwidth and space. Lossless RAW can only achieve mild compression because of entropy - worst case for lossless compression would be totally random noise, best case every pixel has the same value. It is like ZIP or RAR, no data is lost, just better sorted and optimized.

With lossless compression you can expect a ratio of 1.2:1 to 1.6:1 or on the average 1.3:1

Higher compressions like 3:1 or 4:1 use lossy compression after using lossless compression first. Lossy compression will most likely change the look of noise/grain. I'd say there should be hardly a difference between lossless and 3:1 and a mild difference in the shadows noise structure of 4:1.
Robert Niessner
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Rakesh Malik

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Re: SSD RECORDER 4.6K RAW 60P

PostThu Feb 22, 2018 5:46 pm

Tomriechart wrote:If I buy an SSD that is faster than the SSD recommended on your site, can it hold 4.6K RAW 60P?

And is there a problem buying an SSD that is not recommended even though it is faster than recommended?


A LOT of the problems people thought were problems with the BMCC when it was new were actually from SSDs not being up to spec. You're far better off following BMD's recommendations than not. You might end up spending a bit more than on a non-recommended card, but keep in mind that BMD isn't testing the media so that it can sell it to you at a profit, it's testing the media so that BMD's customers can (if they listen) have reliable cameras.
Rakesh Malik
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