KxS: SD as SxS by Guy Barwood

OverCranking with KxS
(Created 24 October 2008: Updated 11 July 2009)
By Guy Barwood - Glass Eye View

Introduction

As detailed on the original KxS page, KxS is not a reliable media for recording over cranked footage. This is due to the limited thoughput of the USB bus on the camera, which is fine for standard HQ 35Mbps but not sufficient for bit rates too much higher than that. To the uninitiated this may seem strange as often there is confusion with bit rates on the EX series with overcranking (called 'slow motion' by the camera) at first.

Here is the reason why. When the EX series recorder slow motion, it records at a data rate based on the playback rate, not the record rate. For example, if your base setting is 25p and you set slow motion recording to 50p you expect to get a full 50% slo motion playback. Therefore the EX will use a 70Mbps data rate at record time, which is halved at playback to return to 35Mbps (standard HQ data rate). This is the only way to maintain the same quality of recording when recording for a slower than real time playback. In a way, you can think of it this other way. What ever the frames per second you set for the recording format (24, 25 or 30), this is the number of frames allocated to every 35Mb. If you slow mo more than this frame rate, then these frames are recorded in less than one second so the 35Mb is allocated to less than 1 sec thereby increasing the effective recording data rate per actual second of recording.

In theory, the maximum data rate is determined by setting the slowest recording frame rate with the highest slow motion frame rate, With the EX1 that is setting the camera to 24p and slow motion frame rate of 60p. That's 35*60/24= 2.5x35 = 87.5Mbps. KxS appears reliable up to 40p when set to 24p format which equates to about 58Mbps. Certainly enough for standard HQ (35Mbps) and possibly even the 50Mbps required by the PWD-700 if the media is recognised by the SxS attachment.

So how can you over crank to 60p wit KxS? Well you can't directly, but all is not lost, you can still leverage KxS with over cranking. Under certain circumstances this solution may suite you. As long as you have some time to copy off the clips, there is no need to lug a laptop along with you too offload SxS cards.

Ingredients:

1: Minimum 1x SxS card
2: KxS media combo (although nearly any SD card that is recognised could work for this.

Recipe:

1: Record your over cranking directly to a SxS card
2: Copy the clips to the KxS card using the camera's copy clip function
3: Eject the KxS card (for safety, you can't format it if it is not inserted)
4: Format the SxS card
5: Re-insert the KxS card & return to step 1