Post Process
Post processing is the stage of the video pipeline that attempts to ensure good quality output for the type of display being utilised - such techniques include de-interlacing of an interlaced source for a progressive output, frame-rate conversions, scaling of the video output to match the desired playback resolution and colour correction.
De-Interlacing is one video feature that has been implemented on many graphics cards, with adaptive techniques between temporal and spatial interlacing being utilised, however the next generation of graphics products with Avivo will introduce vector adaptive de-interlacing. With vector adaptive de-interlacing the hardware attempts to select the best data from which to build the de-interlaced frame from, be that from the raw field data or video data that is interpolated along several vectors.
Avivo also contains both a pre-scaling engine which scales the video from the source resolution to the requested application resolution and a post-scaling engine to fit to the display.
Display
The final part of the video pipeline is the display element, and this also
applies to standard desktop 2D processing and 3D output as well. The display
hardware has to cater for multiple different display types and connections, each
of which have their own characteristics in gamma response, colour space (RGB or
YPrPb), colour response and white point, resolution and aspect ratio, colour
depth and also timings.
Although we've been used to 10-bit per component RAMDAC's in previous graphics parts, this was limited to just the DAC, however with Avivo products there are dual 10-bit per component pipelines prior to the DAC's, operating 1.07 billion colours as opposed to 16.7 Million on standard 8-bit display pipelines. The pipelines perform the following functions at 10-bit precision, and an apply to both video playback as well as standard 2D or 3D operations where needed:
- Gamma Correction
- Colour Correction
- Video Scaling
Each of the 10-bit display pipelines have the complete set of post processing functionality, matched to the properties of the particular display output they are ultimately driving. A single video source can be displayed on two independent outputs each with their own scaling, gamma correction and positioning again, tailored to the output that each are displaying on.
The display engine also features the hardware that actually drives the display output, and Avivo has a number of enhancements here. Dual 400MHz 10-bit per component DAC's remain, as in previous graphics implementations, however this time the TV-Out display engine has been lifted directly from ATI's consumer electronics Xilleon processor (this engine can be found to be driving the displays of many Sony televisions, for example). The last generation of Radeon products only integrated a single link, 165MHz, TMDS transmitter for DVI output, however Avivo products will feature two integrated dual link transmitters, hence two digital panels can be independently driven to 2048×1536 @ 75 Hz or 2560x1600 resolutions.
When an analogue output is used the 10-bit processed image from the display pipeline is sent to the 10-bit RAMDAC's and the image is re-quantized down to 8-bit for display, however the extra two bits are used to, in theory, produce a better resultant 8-bit output. In the case of digital displays, the 10-bit data goes through a spatial and temporal dithering process for 8-bit or 6-bit displays (most modern desktop LCD panels are 8-bit, while many notebook panels remain at 6-bit), however newer 10-bit and 16-bit panels can be driven directly from the Avivo digital display outputs - in the case of 10-bit panels it is kept in the same format as was in the display pipeline, and is outputted as is, and with 16-bit displays the colour depth is up-scaled, although it will remain at the 10-bit processing level.
ATI also point out the benefits of the Avivo display pipeline beyond just video, and are keen to hook on to digital image processing, such as digital photography. ATI maintain that the 10-bit pipelines will better preserve to clarity of the digital image, especially if they are using professional cameras capturing at a higher bit rate, and that can further be taken advantage of if a higher depth display is being utilised.
This range of display engines will allow ATI to support a greater range of connectivity than the traditional analogue VGA and DVI outputs, to more consumer electronics friendly outputs including Euro-SCART and HDMI outputs. To go along with the HDMI outputs Avivo features HDCP capabilities so high definition movie content can be displayed on high definition displays. Consumer electronics displays have a different range of timing modes to PC displays and previous ATI hardware has used software routines to match the timing modes when these displays are being connected to, however Avivo now features a complete set of timings for both PC and consumer electronics standards which should reduce issues such as over scan on TV Outputs.
