Tag Archives: 4:4:4

Look how small the Gemini is!

Gemini-on-AF1001-225x300 Look how small the Gemini is!
Gemini 4:4:4 recorder on Panasonic AF100

Just obtained a picture of a pre-production Convergent Design Gemini mounted on a Panasonic AF101. It really shows just how compact this device is. The LCD is 800×400 resolution and a very bright 800 nits, which is nearly twice as bright as an iphone or ipad! You have to remember that this is not just a monitor but also a 4:4:4 10 bit, uncompressed recorder! With a street price of less than $6k this will be the perfect match for the Sony PMW-F3.


Convergent Design Gemini 4:4:4 Recorder and Monitor… Yum Yum!

Gemini-Side-229x300 Convergent Design Gemini 4:4:4 Recorder and Monitor... Yum Yum!
New Convergent Design Gemini

Well here it is. I’ve known about this rather amazing device for some time, but have been under NDA. I see this as the perfect companion for Sony’s PMW-F3 and with a street price of around $6,000 it’s a bit of a bargain. It is both a 4:4:4 uncompressed recorder and a rather handy monitor (it will do 3D recording and monitoring too), all in a single unit that is no bigger than most high end HD monitors. It records to readily available, cost effective SSD’s and can even make dual recordings to both drives giving an instant backup. It records uncompressed, so you get the absolute best quality possible. If you need an alternative codec then you simply transcode to your chosen codec when you ingest the material in to the edit system. When will it be available? Well CD are hoping to start shipping at the end of July, but that may slip a little, still it should not be too long to wait. Here are some of the headlines from CD’s press kit:

“Gemini enables videographers and cinematographers to capture at the ultimate video quality, in a small, low-power, lightweight package, at a very affordable price.  Gemini features a built-in high-brightness 5.0” 800×480 24-bit LCD touch-screen for monitor and playback, and introduces an industry first – the ability to simultaneously record to two removable solid-state drives – creating instant backups; an invaluable insurance against lost footage, as well as, opening new workflow options.

Building on, but not replacing, the highly successful nanoFlash, Gemini records 10-bit uncompressed 4:4:4 / 4:2:2 video in most popular HD/2K/3G formats, including 1080p24 and 1080p50/60, with up to 16-channels of embedded audio and timecode.  Gemini has slots for two removable 1.8” solid-state drives (SSDs), enabling recording in either parallel mode (instant backup), or spanning mode (longer record times).  Sporting a lightweight milled aluminum case, Gemini is about the same size and weight as the popular SmallHD DP6 monitor, but includes Recording, Playback, Image Processing, Dual HD/3G SDI I/Os, HDMI-Out and consumer level audio I/O; while consuming only 8 to 15 watts of power.

Gemini features S-Log support, with user programmable viewing LUTs, which can be enabled selectively for either HD-SDI output.  Flexible recording options, include simultaneously recording native S-Log video to one SSD (for on-line), and the same footage with burned-in LUTs to the second SSD (for faster creation of off-line proxies and/or H.264 video for mobile devices/internet).

Gemini-With-SSDs-300x168 Convergent Design Gemini 4:4:4 Recorder and Monitor... Yum Yum!
Gemini records on to one or two SSD's

A 3D/Stereo (extra-cost) option will also be available, enabling dual-stream recording and playback in a single Gemini unit; creating the world’s smallest, lowest-power, 3D recorder available anywhere.  Gemini will record independent left/right channel files, while providing full synchronized playback of two streams as well as side-by-side, 50/50 composite, or anaglyph combinations.  Gemini can uniquely output 3D in multiple formats simultaneously (ie side-by-side and 50/50 composite), to aid in camera alignment and monitoring.”

When is 4:4:4 not really 4:4:4.

The new Sony F3 will be landing in end users hands very soon. One of the cameras upgrade options is a 4:4:4 RGB output, but is it really 4:4:4 or is it something else?

4:4:4 should mean no chroma sub-sampling, so the same amount of samples for the R, G and B channels. This would be quite easy to get with a 3 chip camera as each of the 3 chips has the same number of pixels, but what about a bayer sensor as used on the F3 and other bayer cameras too for that matter?

If the sensor is subsampling the aerial image B and R compared to G (Bayer matrix, 2x G samples for each R and B) then no matter how you interpolate those samples, the B and R are still sub sampled and data is missing. Potentially depending on the resolution of the sensor even the G may be sub sampled compared to the frame size. In my mind a true 4:4:4 system means one pixel sample for each colour at every point within the image. So for 2k that’s 2k R, 2K G and 2K B. For a Bayer sensor that would imply a sensor with twice as many horizontal and vertical pixels as the desired resolution or a 3 chip design with a pixel for each sample on each of the R,G and B sensors. It appears that the F3’s sensor has nowhere near this number of pixels, rumour has it at around 2.5k x 1.5k.

If it’s anything less than 1 pixel per colour sample, while the signal coming down the cable may have an even number of RGB data streams the data streams won’t contain even amounts of picture information for each colour, the resolution of the B and R channels will be lower than the Green, so while the signal might be 4:4:4, the system is not truly 4:4:4. Up-converting the 4:2:2 output from a camera to 4:4:4 does not make it a 4:4:4 camera. This is no different to the situation seen with some cameras with 10 bit HDSDI outputs that only contain 8 bits of data. It might be a 10 bit stream, but the data is only 8 bit. It’s like a TV station transmitting an SD TV show on an HD channel. The channel might call itself an HD channel, but the content is still SD even if it has been upscaled to fill in all the missing bits.

Now don’t get me wrong, I’m not saying that there won’t be advantages to getting the 4:4:4 output option. By reading as much information as possible from the sensor, prior to compression there should be an improvement over the 4:2:2 HDSDi output, but it won’t be the same as the 4:4:4 output from an F35 where there is a pixel for every colour sample, but then the price of the F3 isn’t the same as the F35 either!