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19
May
posted by - Wednesday, 19 May 2010

Convergent Design is constantly adding new features to their nanoFlash HDSDI recorder. On their last update they added  overcrank / undercrank recording. Many of our clients have the Panasonic VariCam or the HDX900, and are looking for a tapeless recording option. With high quality-recording and the new variable frame rate recording option, the nanoFlash can really extend the life of these cameras. Check out this quick guide to get your HDX900 or VariCam working with 720 24p recording, 720 30p recording, and overcrank / undercrank mode using the nanoFlash.

First, make sure you are running the latest version of the nanoFlash firmware – available here. It’s an easy install and only takes a couple minutes.

24p Recording –

The VariCam and HDX900 (in 720 mode 59.94) always output a 720 60p HDSDI signal regardless of your frame rate. When shooting 24p video the camera will apply pulldown to produce that 60p signal. The nanoFlash can remove this pulldown with a simple switch. Here are a couple steps.

1. In the video menu set your bit rate and codec. The nanoFlash will record the 720 signal in both I-Frame and Long GOP at all the available bitrates.

2. In the video menu turn on “Remove 3:2 Pulldown”

3. Input your 720 24p camera signal, and after a few seconds you should see the format show up as 720pd23 – the ‘pd’ stands for pull down.

4. Start recording 720 24p native, and because pull-down is removed before recording you get the full quality of your chosen bitrate.

On an HDX900 the same method can allow you to record 1080 24p. Just set your HDX900 to 1080 24p, keep “Remove 3:2 Pulldown” on, and you’ll record true 1080 24p.

30p Recording –

The VariCam and HDX900 (in 720 59.94hz mode) always output 720 60p over HDSDI. In 30p mode it uses a simple 2:2 pulldown method to turn 30p into 60p. The nanoFlash can remove this with a switch in the video menu called “720p 60/50 -> 30/25.” When turned on it will pull out 30p from a 60p signal, or 25p from a 50p signal. Here are a couple steps:

1. In the video menu set your bit rate and codec. The nanoflash will record the 720 signal in both I-Frame and Long GOP at all the available bitrates.

2. Turn off “Remove 3:2 Pulldown”

3. Turn on “720p 60/50 -> 30/25″

4.  Input your 720 30p camera signal, and after a few seconds you should see the format show up as 720h29. It says 29 because your actual recording is 29.97p.

5. Start recording 720 30p native, and because pull-down is removed before recording you get the full quality of your chosen bit rate.

Overcrank & Undercrank -

For full overcrank / undercrank recording, the nanoFlash will accept a 720 60p signal and allow you to set a recording rate and crank rate. Let me explain what this means.

The 60p signal comes in and I can choose the frame rate I want it to record to – Recording Rate – which is the format that I want to deliver the material in.

For example: I want slow motion or fast motion material, but I want everything delivered in 720 24p.
I would set my Recording Rate to 24p regardless of the actual fps I’m capturing.

In the Crank Rate setting I adjust the actual speed I want to capture between 1-60 fps.

For example: I want to record slow motion in 24p, so I set my Record Rate to 24p
and my Crank Rate to 60fps. This will produce a 2.5x slow down.       OR

I want to record fast motion in 3op, so I set my Record Rate to 30p and
my Crank Rate to 1fps.

Here is a couple steps to set this up:

1. In the video menu set your Codec to I-Frame and your BitRate to above 50 Mbps. You must be set this way for overcrank/undercrank settings.

2. Turn off “Remove 3:2 Pulldown”

3. Turn off “720p 60/50 -> 30/25″

4. Turn on “Crank” and set your Recording Rate (the first number) and Crank Rate (second number).  Typically it would be set to 24 record rate and 60 crank rate for slow motion 720 24p video.

5.  Input your 720 60p camera signal, 24p or 30p will not work. After a few seconds you should see the format show up as 720p59. It says 59 because your actual recording is 59.97p.

5.  Start Recording your video. You should see your Crank Rate below your time code when recording.

Make sure to turn off these settings for normal recording. The nanoFlash and the VariCam/HDX900 really seem to be a winning combination.

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