Description

The 2246 is a USB 2.0 A/V (audio and video) MPEG-1/2/4 (MPEG ISO 14496-2) processor that supports multiple video input formats, including SDI 1080i, 720p, and both SDI and analog NTSC/PAL SD. It compresses video and stereo audio to MPEG-1 system stream, MPEG-2 program stream, or MPEG-4 (AVI), and sends the resulting stream onto USB. At the same time, it can capture uncompressed full-frame snapshots and send them over USB, while it simultaneously generates live or freeze frame video on its four video outputs.

Simplified 2246 dataflow diagram

At any time, one HD or SD video source (HD-SDI/SD-SDI, S-Video, or composite) and one audio source is selected for processing. The selected video is copied to three independent overlay generators, which in turn produce three new uncompressed, overlaid video streams. These three video streams are then processed in parallel by the compression engine (along with audio), video output generators, and frame capture subsystems.

Audio may be sourced from embedded SDI audio, external audio line in, or external microphone signals. Audio can be output to embedded SDI, line out, MPEG stream, or any combination of these.

The compression engine simultaneously compresses SD video and stereo or mono audio. When an HD video source is selected, the overlaid video is downscaled to SD before encoding.

All four video outputs (HD-SDI/SD-SDI, DVI, SVIDEO, and composite) function simultaneously regardless of the video source format. In the case of HD sources, the video is downscaled for compatibility with composite and S-Video outputs. SD sources are upscaled as appropriate for the DVI output. The DVI output, which may be formatted for 1080i, 1024x1280p, or NTSC/PAL resolution, incorporates frame rate conversion to ensure synchronization to standard displays.

A frame buffer is provided to capture uncompressed snapshots of individual frames. Captured frames can be sent over USB concurrently with the video stream, and may also be sent to the video outputs as freeze frame video.

The 2226 sports a zoom feature on the MPEG and DVI output streams. Video can be stretched up to 2.5x horizontally and 5x vertically, with origin moved to any arbitrary position. Video zoom is performed by the scaler blocks.

The unit is available in a robust enclosure (model 2246S) or as a stand-alone board (model 2246) for OEM applications. An optional termination board adapter, Model 2246TA, can be used to conveniently break out connections from Model 2246.

Model 2246: bare board version for OEMs

Video Overlay

Model 2246 supports text and graphic overlays at 16-bit color resolution. Eight overlappable, hardware-managed regions are supported. Each rectangular region may occupy up to full screen size. Any true-type font can be displayed. Graphics can be displayed from standard .bmp files as well as generated on the fly by Sensoray's 2246 API. The API allows graphics to be easily placed and moved anywhere on the screen. Real-time update rates are possible for small overlay regions, while update rates for larger regions vary depending on computer speed and USB activity.

Each overlay region may be applied to the compressed stream, the live video output stream, the freeze frame video, or any combination of these. In the case of the MPEG stream, the video is overlaid before it is compressed.

Sample snapshots of HD full-screen overlay

Video pass through

The board includes special circuitry which will, in conjunction with an external power supply, enable video inputs to pass through directly to the video outputs (without reformatting). This feature is useful in the event of primary power loss or if the host computer is offline.

General purpose digital I/O

The 2246 has eight digital inputs and four digital outputs for general purpose use. The inputs are optically isolated, while the outputs employ compact electromechanical relays. Each output relay has two form-C contacts.

Software Development Kit (SDK)

A windows driver is supplied for software developers. The driver contains a low-latency MPEG software decoder that will decode the audio and video on the MPEG stream sent from the 2246. A comprehensive Windows demo program is also included with the SDK.

Windows demo program

Evaluation System

An evaluation system, Model 2246S, brings out the circuit board's signals to conventional connectors. Its aluminum enclosure shields sensitive circuits and protects the 2246 from physical damage.

2246 Evaluation System