As HD (>2 megapixel) image sensors become mainstream, and flash memory continues to fall in price, high quality HD video compression is being added to webcams. Their presence is expected to grow in both home and office environments, although the biggest challenge remain that of channeling the higher amount of information through WiFi and internet channels.

Key facts:

• In-camera encoding allows lower bitrates and support for internet applications at HD resolutions
• Multi-format support for H.264 (Quicktime) and VC-1 (Windows Media)
• Software upgrades to support Flash, MJPEG, MPEG-4, etc.
• on-chip image preprocessing allows real-time graphics to be encoded with the stream
• Smaller package for low pin-count, low power and low cost

The biggest limitation in the adoption of HD webcams, being it in the home as consumer devices or in the office as videoconferencing hubs, it the data bottleneck constituted by the transport network. As the table below shows, classic motion-JPEG (MJPEG) compression can typically reduce the datarate typical of HD images to a size suitable to be transferred to the home PC (or office server) through a USB 2.0 cable. The resulting stream is however still too large to be streamed either through a home WiFi network or the internet and it needs to be resized to resolutions of 640x480 or less. The table below illustrates the bandwidth requirements for different stream resolutions through progressively more contentious mediums.

Offloading the task of recompressing the webcam image to the PC or server is also not realistic. A logical canditate for streaming is H.264/AVC, a standard developed to provide high quality images at very low-bitrates. Transcoding to H.264 is however very computationally intensive and real-time HD H.264 transcoding is still far beyond the capability of any home PC or, for that matter, office server.

Q offers a solution in which encoding is performed at the source, in the webcam, and streamed to the PC/Laptop/Server (although a host based solution is also possible, as explained here). Aspex Q pre-processing capabilities and software programmability also ensure that typical webcam fun features can be integrated right on at the source, de-facto alliviating the host of any extra computation. The bitrate reduction is such that HD streams can easily be used for videoconferencing and/or security in the home and in the office as well as being uploaded through a broadband connection in real-time.

The table below shows the bandwidth impact of implementing H.264/AVC encoding on the source.

Finally, Aspex Q flexibility means that it is backward compatible with existing MJPEG capable software and devices, while also being able to generate H.264/AVC streams (Quicktime, Flash Player) as well as VC-1/WM9 (Windows Media).