We have been developing a handheld technology demonstrator capable of receiving DVB-H broadcast, decoding the 3D video streams and playing them on an auto-stereoscopic display (see Fig. 1). The core of such device is a multimedia-reach platform with sufficient computational power to handle the high amount of data.
The selected development platform is OMAP 3430 manufactured by Texas Instruments. Demanding applications such as stereo-video decoding and playing, can be parallelized employing different cores with sufficient speed provided by the high clock rate. Specifically, the OMAP 3430 features a superscalar ARM Cortex-A8 RISC core, an image video and audio (IVA) accelerator enabling multi-standard (MPEG4, WMV9, RealVideo, H263, H264) encoding/decoding at 720x480 pixels and 30 fps and an integrated image signal processor (ISP). Graphics accelerator with OpenGL CE support is integrated as well. The available XGA display support allows for choosing high-resolution LCD. Advanced power reduction technologies enable the implementation of power-demanding applications such as rendering stereo-video with increased backlight. Various interfaces allow for easy embedding extra modules, e.g. the DVB-H front-end. The support of high-level operating systems is also a key factor for rapid application development. Fig. 2 shows the block diagram of the OMAP3430 processor.
A selected DVB-H receiver is being integrated to this platform.
Two auto-stereoscopic displays have been interfaced to the platform. Currently, the prototype interfaces an auto-stereoscopic 3D LCD display model MB403M0117135 produced by MasterImage, which is a 4.3"WVGA (800x480 pixels) transmissive LCD display. The second display interfaced has been developed by NEC LCD Technologies. It is based on lenticular technology. In contract to other known displays of this class, the pixels in the NEC's design are twice more dense in horizontal than in vertical direction, an arrangement called Horizontal Double Density Pixel (HDDP) arrangement. The display is able to work both in transmissive or reflective mode, which ensures 3D operation in wide range or lighting condition. It is 3.1 inch, with WQVGA resolution both in 2D and 3D mode. Tests with that display showed that it offers excellent capabilities in terms of stereo effect, angle of view and low crosstalk.
In order to ensure stable and proper functionality of the platform - an appropriate OS need to be chosen. It must conform all the requirements of the peripheral hardware (DVB-H receiver and autostereoscopic module), all the requirements concerning the signal processing, and to provide fundamentals for easy further development.
The software development consists of:
For the first version of the terminal device, the H.264 simulcast approach has been implemented. Simulcast allows manipulating and experimenting with videos of different quality (varying quality factors such as bitrate, framerate, transmission modes, etc.) - simply code and decode the streams and put the left and right channels side by side to be played further in the subjective tests.
The two-channel video, i.e. left-eye frame and right-eye frame coming out of the decoder has to be converted for the respective display. Fig. 3 illustrates the process of interleaving of left and right views for the case of parallax-barrier display.
Display support was developed as OMAP 3430 TI Linux baseline display drivers for the two displays under consideration. This component combines left and right views from the output of the H.264 decoder to produce the format required for driving the respective auto-stereoscopic LCD display.