High Definition (HD) vs. Standard Definition (SD) Video Capture Options

[Scott McDowell]

We often receive requests from our customers and partners for recommendations regarding capturing live HD video from a digital cable or satellite receiver. Although live HD capture is technically possible, I often recommend that they consider capturing in SD instead. Below I have included brief explanations regarding the factors that will affect this decision. This information is intended to prompt our customers and partners to weigh both options but it is by no means an exhaustive comparison of video capture technologies.

Cost and Availability
Hardware MPEG-2 SD capture devices are inexpensive (~$100) and available from many different manufacturers.

True HD capture devices (i.e. devices that can capture at 720p and higher) start at a much higher price point (~$200) and the less expensive models are generally software based. There is also currently less selection as the devices tend to be aimed at video professionals and not home consumers.

Interface Options and Form Factors
SD capture devices are available for PCI, PCIe/PCIExpress, and USB 2.0+. For internal capture cards, you have many options for both full and half-height slots.

HD capture devices are only available for PCIe/PCIExpress and USB 3.0, due to the additional bandwidth requirements. USB 3.0 is currently (Q4 2010) not a standard feature on most computers due to the lack of USB 3.0 support in most system controller chipsets, though this will likely change towards the second half of 2011. The limited options available for HD capture form factors means that you must ensure that your computers will have the necessary ports and will be able to physically fit the capture device.

Performance Impact
Hardware MPEG-2 SD capture devices can capture live video with very little impact on the rest of the system resources. This is due to the hardware included in the devices that handles most of the video encoding and decoding.

Most affordable HD capture devices rely heavily on the system CPU to handle video encoding/decoding. This can have a major impact on the system resources available for rendering the rest of your signage content.

Resolution and Screen Area
SD capture devices typically capture at 480p (720x480@30 fps progressive) (NTSC/North America) so this leaves a lot of screen area that can be filled with other content.

HD capture devices can usually capture at either 720p (1280x720@30 fps progressive) or 1080i (1920x1080@30 fps interlaced). This means that far more of the typical signage display will be consumed by your captured video. (Note that generally 720p "looks better" than 1080i due the tearing inherent with an interlaced video signal. Most users I have dealt with opt for 720p.)

Encryption and Copy Protection
Note that Omnivex does not endorse the use of copy protected content as part of your signage system without permission/license. However, there can be instances where you have permission to display content, such as live TV, in a public space but copy protection or encryption technologies will still get in your way.

SD signals are analog and, aside from technology such as Macrovision that is often included on commercial DVD releases, can usually be captured without concern for copy protection mechanisms. In particular, SD live TV is often available with copy protection.

HD signals can be either analog (e.g. component) or digital (e.g. HDMI) and it may not be possible to circumvent certain copy protection such as encrypted digital TV. Although your digital cable or satellite receiver may have a digital output, it may not be possible for this output to be used with a computer capture device due to copy protection that is put in place to prevent the recording and distribution of digital broadcasts. The bottom line is that even if a digital receiver and a capture device will physically connect together, there is no guarantee that you will be able to capture the signal.

Quick Comparison of Typical Capture Devices

	SD	HD
Cost	$	$$
Interfaces	PCI, PCIe, USB 2.0+	PCIe, USB 3.0
System Performance	Minimal Impact	Affordable hardware usually has a high CPU consumption
Resolution	480p (720x480)	720p (1280x720) and 1080i (1920x1080)
Encryption	Typically not an issue	Usually depends on the connection type and capture source

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In the end, it is up to you to decide whether SD or HD video capture best suits your project. Omnivex software is capable of handling both options, provided the computer hardware you have selected is up to the task of capturing and rendering the content that you have designed. Please browse this forum or contact Omnivex Technical Services if you have questions regarding recommend capture hardware. We have designed our software to be very flexible but we still cannot guarantee that every capture device will function as expected in our software.