Monthly Archives: January 2014

Frame Synchronisation

High speed cameras are often synchonised, (aka genlocked, framelocked) together. All but the most basic cameras include the ability to input or output a sync signal for this purpose. Creating movies with frames captured at exactly the same instant has many uses, including:

  • A Y-Series camera, with GPS antenna attached

    A Y-Series camera, with GPS antenna attached

    Accurate motion analysis of an event with cameras at multiple viewing positions

  • 3D imaging

If there are two cameras located close to each other, the simplest way to configure the cameras is connect the camera together with cabling. For larger number of cameras or large distances between cameras, this can get quite messy or very difficult to configure. In many outdoor testing environments, the length of cabling required often result in frame sync’ing being desired, but not actioned.

NX-Air Camera

NX-Air camera, showing GPS connection on left hand side

Instead of cabling, a GPS timing signal* can be used. If the camera includes GPS (like IDT’s NX-Air and Y-Series cameras), the internal clock of the camera is locked to the timing pulse of the GPS signal, so all cameras are totally in sync with each other. All that’s needed is a low cost GPS aerial connected to the GPS connector on the back of the camera, then choose GPS from the frame sync dropdown in the control software. There is no limit to the distance between cameras, so even if the cameras are miles apart, they can still be frame sync’d.Y-GPS Cable free sync’ing is also useful for indoor tests (eg where the cameras are on board a test vehicle and a trailing cable is not possible). GPS sync’ing can still be achieved indoors, with the addition of a GPS repeater, which receives a GPS signal externally, then transmits inside the building.

For more details on GPS synchronisation, please contact IDT

  • How to configure cameras for GPS sync’ing
  • What extra hardware is required?
  • Which cameras can be wirelessly sync’d?
  • Can everything be wireless (control, download, triggering…)?

*GPS satellites are more often associated with positioning (satnav etc), but a single GPS satellite only transmits a (very accurate) timing signal. Positional data is obtained by triangulating from 3 or 4 satellites.

Understanding Memory Types

The two critical components in all digital high speed cameras are sensors, which have to get rid of an image very quickly in order to capture the next, and memory, which has to accept data at a phenomenal rate.

computer-ram

Several different memory types are used.

  1. RAM in the camera. The majority of high speed cameras use high speed RAM (Random Access Memory), due to the ability to accept data at very high rates. The quality and grade of the RAM has to be high, which adds to the value of a camera, particularly the higher frame rate and higher resolution models. RAM is volatile, to the images need to be transferred to permanent memory (HDD or SSD etc) before power is lost. For this reason, many high speed cameras (including IDT’s NX-Air) incorporate a battery, increasing the integrity of the images.
  2. RAM in the PC. Some high speed cameras (including IDT’s M-Series) don’t include memory themselves, but record to the RAM of a PC via various interfaces (The M-series cameras use CameraLink). Because of the interface and the variable quality of PC’s RAM, the frame rates are restricted compared to the camera having its own RAM. After the recording, the sequence needs to be transferred to permanent memory as per the cameras RAM.
  3. HDD in the PC. Again, like PC RAM, the frame rate is restricted, as HDD cannot accept data at very high rates. High speed cameras configure to a PC’s HDD have the benefit of very long record times, even of the frame rate and resolution are not that high. SSD in the PC is slightly faster, but often cameras won’t frame faster as the system is configured for all PC’s in the same way. IDT’s M-Series can record direct to HDD or SSD of your PC, enabling very ling record times.
  4. SSD in the camera. Solid State Disk has the benefit over HDD of having no moving parts, so can accept data faster (not as high as RAM) and is rugged enough to be used in high speed cameras for Hi-G applications (crash tests etc). Still not as fast as camera RAM, but it has the advantage of being permanent. The capacity of SSD memory modules is higher than RAM, so longer record times are possible, but the rate that data can be saved to RAM is still higher, so for the highest frame rates/ resolutions, RAM is still the best choice. IDT’s new Os Series includes RAM and SSD, for the ultimate in versatility.

The RAM and SSD in IDT’s Os Series cameras offers several operation modes:

  • RAM only. The Os Series camera operates just like a high speed camera which only has RAM
  • SSD Backup. VERY fast downloads from RAM to permanent memory, releasing the RAM in the shortest time ready for the next recording, and ensuring the shortest time before the images are safe in case of power loss. Downloading the images starts even before the images have finished recording!
  • SSD Streaming. Recording direct to SSD allows longer recordings, which are permanent straight away. Although this is a slower rate than recordings to the cameras RAM, is allows far higher rates than the direct-to-PC recording detailed above, and keeps the benefit that the camera can work alone, not being connected to a PC during filming. IE the camera can record long sequences with no PC connected in applications like car crashes, airborne tests etc.

The Os Cameras include 8GB RAM and 0.5TB SSD. The camera can also be programmed to perform a variety of the above modes sequentially for complex test sequences.

See details of the OS-Series Cameras

This article doesn’t talk about removable media (CF, SD etc). Contact us or comment below if you have questions on removable media

 

Understanding Resolution

Image resolution is measured in pixels – or picture elements; the dots that together make up the image. This article focuses on video resolution, although many aspects of course apply to still images too.Resolutions

When digital displays first became commonly used, they tended to be VGA resolution (640×480 pixels). Over the last few years the resolution has steadily increased, with Full HD (High Definition, 1080p – 1920×1080 pixels) being most common. The chances are your flat panel TV and your computer monitor are both this resolution. The other change you’ll have noticed is the widening of the screen aspect ratio to 16:9 rather than 4:3 (the ratio of the horizontal to vertical dimensions)

Video cameras and camcorders have unsurprisingly followed these changes too. Today the vast majority of video cameras are full HD resolution.

2014 will see a big emphasis on the next resolution change – 4K. This resolution is 4x the resolution of HD, 3840×2160 pixels. As the demand for larger and larger TV screen sizes continues, 4K will become the norm for the larger sizes.

Several factors have been instrumental in the advancement of resolution

  • Sensor technology – the ability to squeeze more pixels on the sensor
  • Processor speed – faster processors allow data to be transferred from sensor to memory more quickly
  • Memory – The memory needs to be able to accept data at the rate that the images are being generated

In high speed cameras, these three factors are pushed to the limits. Manufacturers such as IDT are continually pioneering faster and higher resolution sensors to include in their cameras. The data rates (a combination of resolution, frame rate and image depth) are significantly above standard video cameras. Standard video cameras generally frame at 25 or 50 images per second.

Two sensors are available from IDT with 4K resolution, both available in the Os Series camera. The Os10 can frame at up to 1,200 frames per second at 4K resolution. As the data rate is the limiting factor, the frame rate can be increased as the resolution is proportionally reduced.

That’s all very well, but what resolution do I need?

People get very hung up on resolution… “My phones got a resolution of 8 megapixels” we often hear, which sounds better than many decent digital cameras, which ‘only’ have 6 Mp sensors. Well, there’s a lot more to creating good images than just the resolution. The quality of the sensor, sensor noise, the lens; I could go on…

Choosing the best resolution for your application all depends what you’ll be using the imagery for. If you’re displaying on a monitor for general viewing, then HD is a good resolution to use, but a decent image of a particular event for scientific purposes need not be more than 512×512 or 1024×1024 pixels. Larger image resolutions should be chosen if (for instance)

  • displaying on a large monitor (a massive 4K monitor or multi-screen) or
  • if the image could be cropped afterwards, as the exact location of the event cannot be determined beforehand, or
  • if very high positional accuracy is required

To discuss what resolution would be most suitable for your application, contact IDT now.