Blackmagic Forum

I saw something about pre-recorded, just wondering which cameras would be included in this, would love my micro studio G2 to have this...

This is a new feature to be implemented so its anyone's guess. Grant demoed it with a Pyxis 6K, so I'm assuming that camera (and the cameras above it) should get it. He did seem to give the impression that they will implement other cameras as well, but didnt give specifics. As this kind of pre-recording is both quite processor and energy intensive (basically the camera is always recording and writing) I don't think its likely many of the older cameras will get it unfortunately.

Paul Jonathan wrote:As this kind of pre-recording is both quite processor and energy intensive (basically the camera is always recording and writing) I don't think its likely many of the older cameras will get it unfortunately.

I don't think it's writing because that would kill cards much quicker. Generally pre-recording holds a certain amount of compressed frames in a RAM buffer at all times and that buffer is quickly dumped to the recording media when the record button is pressed. It will try to write buffered frames to the media as quickly as possible so it can catch up with the live frames.

I don't see why it couldn't be possible on older cameras as long as they have a decent amount of un-utilized RAM for the buffer. I'm pretty sure all of their cameras can already cache a certain amount of frames just so the camera can better tolerate spikes in bit-rate that the recording media can't hold.

zCam does it directly on the cards. Its not that much voodoo as you think it is. cards are fast nowadays and if you can record to a samsung pro ssd its also super cheap.

Rick Baer wrote:zCam does it directly on the cards. Its not that much voodoo as you think it is. cards are fast nowadays and if you can record to a samsung pro ssd its also super cheap.

It's not the speed of the cards that's necessarily the issue, it's the fact that all flash media can be written to a limited amount of times before it will fail. Writing to a card constantly when not recording will kill the card a lot faster.

For that reason I'm seriously doubting Z Cam writes the pre-roll to the card. It wastes power, it's less reliable, and is irresponsible use of the card.

I also hope Pre-Record comes to the URSA Cine models. It's a useful feature. At times you need it even in narrative filmmaking. So that would be a welcome update.

timbutt2 wrote:I also hope Pre-Record comes to the URSA Cine models. It's a useful feature. At times you need it even in narrative filmmaking. So that would be a welcome update.

It makes sense that it would. It's possible that they won't be able to do the longest times at the highest resolutions and framerates, but even a few seconds can be amazing. Sports and wildlife benefit particularly.

@Mark Grgurev & @Rick Baer: I believe Grant mentioned in the keynote presentation that the camera is not writing to the card but to a cache instead and then dumping that data to the card when you hit record. It seems like quite a few Blackmagic cameras have that cache already built in, probably to avoid dropped frames and such, and they have now decided to make it available for the pre-record feature.

Grant presented the feature at 10 second pre-record on a Pyxis 6K in 6K Open Gate 8:1 recording and mentioned it will come to the Ursa Broadcast G2 and Pyxis first ("in a few weeks") but will come to other camera models eventually.

I would still really appreciate a clarification from Blackmagic regarding which cameras they are planning to implement this feature for and what the pre-record times will be for different resolutions. Kristian or CaptainHook care to comment?

Paul Jonathan wrote:Grant presented the feature at 10 second pre-record on a Pyxis 6K in 6K Open Gate 8:1 recording and mentioned it will come to the Ursa Broadcast G2 and Pyxis first ("in a few weeks") but will come to other camera models eventually.

I would still really appreciate a clarification from Blackmagic regarding which cameras they are planning to implement this feature for and what the pre-record times will be for different resolutions. Kristian or CaptainHook care to comment?

If we knew what frame rate that would be at then we could figure out how large the cache is. If it's 30 fps then it would be 1.4GB so at 6K 17:9 it would fit 12.6 seconds. I'm assuming older cameras like the Pocket 4K have less free RAM but since it shoots at 4K DCI max, it would only need 510MB to store 10 seconds of 30fps 8:1 compressed BRAW.

It was 24 FPS, so a bit less than what you calculated. But I think you are right assuming the cache would have different size between camera models no? So that would only allow inference for the Pyxis 6K

Paul Jonathan wrote:It was 24 FPS, so a bit less than what you calculated. But I think you are right assuming the cache would have different size between camera models no? So that would only allow inference for the Pyxis 6K

Oh! Yea, that would be 20% less so it would be like 1.12GBs. And yea, it would be different sizes on different cameras. You could probably get an idea for large the cache is currently on each camera but just picking a recording mode that's way too fast for the recording media and see how long it takes to stop recording.