HD video content is becoming rampant as more countries transition to DTV, and delivering HD content in a bandwidth-limited channel has become a challenge in itself. Catering to demanding broadcast and professional video applications requires a compression/decompression standard that allows no compromise in quality of content that has to be broadcast over a bandwidth-constrained network. To meet this demand, technology manufacturers are already rolling out products that include H.264 as the de facto standard.
Benefits of H.264
H.264/MPEG-4 AVC (MPEG-4 Part 10) video coding is standardized by the ITU-T in association with the ISO/IEC MPEG, together called the Joint Video Team. To cater to a wide variety of applications, ranging from low-data-rate, low-resolution consumer applications to high-quality content creation applications, the H.264 standard supports various profiles, including Constrained Baseline, Baseline, Main, Extended and High Profiles, as well as extension to existing profiles, called Fidelity Range Extension (FRExt). The latest extension to the standard includes Multiview Video Coding (MVC) for 3-D applications.
Broadcast and professional video applications require high-quality video at higher frame rates, such as 1080p60 performance. High Profile supports varied chroma subsampling formats (4:2:0, 4:2:2 and 4:4:4) with greater color bit depth ranging from 8 bits up to 12 bits and resolutions ranging from QCIF (176 × 144) to full HD (1920 × 1080), both progressive and interlaced scanning. It also supports adaptive block-transform switching between 4 × 4 and 8 × 8 macroblock and weighted prediction for scene changes.
The latest developments in the standard, in such areas as aspect-ratio and color-space conversion, are specifically beneficial to professional video applications. Other standard features of H.264 include: multiple reference pictures, intra/interpicture prediction, motion compensation/estimation, temporal and spatial coding techniques, deblocking, entropy coding (CABAC/CAVLC), and a network abstraction layer (NAL) unit.
H.264 video provides better picture quality for a given data rate compared to its predecessors at the cost of higher computational power for compression and decompression, which leads to various implementations using standard PCs/servers, embedded processors, application-specific signal processors (ASSPs), digital signal processors (DSPs) and field-programmable gate arrays (FPGAs).
DSP vs. FPGA
DSP- or FPGA-based custom hardware is popular for broadcast and professional video applications. Today, with higher-performance FPGAs being available, FPGA seems to be a better alternative for such demanding applications. These implementations are now possible using a single FPGA, which otherwise would require a farm of DSPs to do the same job. FPGAs also provide the same degree of flexibility as DSPs, making them more attractive.
CoreEL's H.264 High Profile decoder
CoreEL offers high-performance, high-quality and robust H.264 video decoding solutions on FPGAs for broadcast and professional video applications. Its H.264 hand-coded, real-time logic decoder is optimized for FPGA architectures, delivering higher performance at a lower clock speed and smaller memory footprint.
The decoder runs on a single FPGA and decodes H.264 HD and SD resolutions. It is also multichannel-capable with an optimal number of channels decoding simultaneously. The company's H.264 decoder solution is rich in features and comes in various configurations for different applications. (See Table 1.)
Panasonic made a breakthrough in high-end broadcast and profesional video cameras and recorder/players by introducing H.264 technology with Intra-frame-only processing branded as AVC-Intra, which is used at very high bit rates, such as 50Mb/s and 100Mb/s. AVC-Intra has now become de facto technology in many of the upcoming cameras from various other manufacturers.
CoreEL has developed an AVC-Intra decoding solution (See Table 1.) and has tested it for such compliance using professional-level bit streams. Among other features, the solution includes robust error handling and error concealment features. The entire stream is divided into independent NAL units, and if any errors are detected, then the decoder stops decoding that particular NAL unit packet and continues to decode the next good NAL unit packet.
The design is also flexible and modular to meet the requirements of a wide array of applications. The decoder solution can be customized to achieve the desired bit rate, frame rate, resolution modes, chroma formats, bit depth, etc., and to decode multiple streams simultaneously. CoreEL's H.264 decoder supports a lower gate count and block RAM requirements, as well as a highly pipelined, scalable architecture for broadcasters transitioning to DTV.
Ravi Srinivasan is assistant manager of technical marketing at CoreEL Technologies.
Table 1. CoreEL's H.264 HP and AVC-Intra decoders come in various configurations for broadcast and professional video applications. H.264 decoder Supports High, Main and Constrained Baseline Profile decoders Programmable color bit depth up to 12 bits Supports 4:2:0, 4:2:2 and 4:4:4 chroma formats Supports resolutions up to 1920 × 1080 Supports progressive and interlaced video inputs Supports frame rates up to 60fps for progressive HD decoding Supports high bit rates Simultaneous multichannel decode Validated on custom-built hardware using ITU-T, Fraunhofer and stress streams AVC-Intra 50 decoder CABAC-only entropy coding Bit rate at 50Mb/s Supports 1920 × 1080 resolution, High 10 Intra Profile at Level 4 Supports 1280 × 720 resolution, High 10 Intra Profile at Level 3.2 Support for 4:2:0 chroma sampling format and 10-bit color depth Frames are horizontally scaled by 3/4 (1920 × 1080 is scaled to 1440 × 1080 and 1280 × 720 is scaled to 960 × 720) Supported frame rates for 1440 × 1080 include 60i, 50i, 30p, 25p and 24p Supported frame rates for 960 × 720 include 60p, 50p, 30p, 25p and 24p Supports all Intra prediction modes — 4 4, 8 × × 8 and 16 × 16 AVC-Intra 100 decoder CAVLC-only entropy coding Bit rate at 100Mb/s Supports 1920 × 1080i/p and 1280 × 720p resolutions Supports High 4:2:2 Intra Profile at Level 4.1 and 10-bit color depth Supported frame rates for 1920 × 1080 include 60i, 50i, 30p, 25p and 24p Supported frame rates for 1280 × 720 include 60p, 50p, 30p, 25p and 24p Supports all Intra prediction modes — 4 × 4, 8 × 8 and 16 × 16