Panasonic's AVC-Intra codec - TvTechnology

Panasonic's AVC-Intra codec

The codec preserves quality while decreasing data rates.
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Table 1. Approximate record times for various formats and AVC-Intra codecs.Select table to enlarge.

Since Panasonic Broadcast began incorporating the AVC-Intra codec in select P2 HD equipment three years ago, the codec itself has not undergone any essential changes. The compression technology features bit rates of 50Mb/s and 100Mb/s, using the High 10 Intra and High 422 Intra profiles of H.264, respectively.

Developments, however, have been dramatic on the product side. Panasonic now offers the codec as a standard feature in a growing number of camcorders, field recorders and workflow tools. As significantly, virtually all our partners — companies such as Adobe, Apple, Avid, Grass Valley, Harris and Omneon — now offer native support of the codec. Broadcasters can now realize, end-to-end, the speed and ease of a P2 file-based workflow coupled with the quality bump of AVC-Intra production.

AVC-Intra is the implementation of the H.264/AVC-Intra-only compression in P2 HD products. This efficient video coding standard provides production-quality HD at bit rates more normally associated with ENG applications by enabling the full-resolution, 10-bit field capture of high-quality HD imagery in one-piece camcorders.

Designed for broadcast

The codec provides 10-bit intraframe encoding in two modes: AVC-Intra 100 for mastering video quality and AVC-Intra 50 for very high image quality at a significantly lower data rate.

As an intraframe approach, it captures and preserves the greatest amount of information while offering the greatest flexibility. Unlike long-GOP approaches, it was explicitly designed and optimized for broadcast and production use rather than low-bandwidth distribution.

AVC/H.264 is a codec family with both intraframe and interframe compression implementation profiles. Interframe compression (long GOP) is typically used for content delivery and packaged media; in this mode, its efficiency is unequaled. However, any image manipulation or processing will severely degrade the image quality in long-GOP compression schemes. By contrast, intraframe compression processes the entire image within the boundaries of each video field or frame. There is zero interaction between adjacent frames, so its image quality stands up well to motion and editing. Intraframe compression is used most often for broadcast and production applications where such image manipulation is normal. AVC-Intra takes this process to new levels when it combines the advantages of H.264/AVC software encoding tools to increase the coding efficiency, doing so without the editing/generational quality limitations associated with long-GOP coding schemes.

VSLI available today can handle added computational complexity as is applied in AVC-Intra. The same can be said for the latest multicore CPUs. This processing power can be applied to more sophisticated compression tools such as intraframe prediction or entropy coding customized to image content.

Technical details

Because P2 files are not bound by the format conventions of video signals or linear tape recording, 24p is recorded natively with no need for pulldown or redundant frames. This reduces the required data an simplifies the file and associated time code.

Supported formats and frame rates include 1080 progressive video (23.98p/25p/29.97p), 1080 interlaced video (50i and 59.94i) and 720 progressive (23.98p/25p/29.97p/50p/59.94p). It is recorded in MXF files when stored to P2, tape or disk, or sent over network data links, and exchanged over IP networks and storage systems in the same manner as DVCPRO P2 content. The MXF operating pattern is OP-ATOM, a simple, efficient and preparsed system, permitting easy access to audio/video data as well as XML metadata, proxy and bit maps for easy access to the content. Due to the flexible, IT nature of the file-based P2 recording system, both AVC-Intra and DVCPRO file formats of all video standards and frame rates can reside on the same P2 card.

AVC-Intra 50, targeted at broadcast applications, is an efficient compression scheme, especially when considering the high quality of the video. This compression format uses horizontal resolutions similar to that of existing compression technologies, yet provides double the recording time on P2 cards, a powerful solution that cuts media storage and distribution costs. The storage and bandwidth savings, without the compromises of long-GOP compression, allow it to provide subjectively similar video quality to DVCPRO HD at half the bit rate, a plus for news and bandwidth-efficient requirements. While the compression format uses a 4:2:0 sampling structure, careful color channel filter processing and subsequent resampling, combined with the codec's 10-bit intraframe nature, provide top-quality video.

The hardware

The codec was initially implemented in Panasonic's AJ-HPX3000 2/3in 1080p 2.2-megapixel P2 HD camcorder and as an option in the multiformat AJ-HPX2000 2/3in 1.1-megapixel P2 HD camcorder and the AJ-HPM100 P2 mobile recorder/player. As of March 2010, it is offered as a standard feature in the AJ-HPX3700 and AJ-HPX2700 P2 HD VariCam camcorders, in the AG-HPX300 P2 HD camcorder, and in several workflow tools (the AJ-HPM200 P2 Mobile, AJ-HPG20 P2 portable recorder and just-announced AG-MSU10 media storage unit, which will be available later this year).

The 2010 NAB Show finds us in the enviable position of having an array of broadcast-oriented products that, with the implementation of AVC-Intra, deliver a fast, easy workflow at the highest production level.

Michael Bergeron is group manager and strategic technical liaison at Panasonic Broadcast.