Revisiting 1080p and beyond
Dec 15, 2006 9:00 AM
A number of readers have commented via e-mail about the “Beyond 1080p” article in the Nov. 18 “Transition to Digital.” The topic seems to have hit a nerve. Readers raised questions about implementing a 1080p production infrastructure and methods of distribution.
Production distribution
John Luff, television technology consultant and SMPTE Fellow, expressed observations about the viability of production infrastructures being able to produce content in 1080 60p, let alone 2K resolutions. He pointed out that:
….8-bit, not 10-bit sampling, … for production would be inadequate [and] 4:2:0 coding will sustain for home use into the future, which might be a stretch when people commonly get higher resolution displays… progressive scan formats compress better as well, which probably makes up for the 8-bit/10-bit differential plus a little, but only for home distribution, not production. There is a sentiment on the part of many in production that 12 bit would be better, especially when many output formats including 1080p60 are considered.
…the complete format [of] SMPTE 292M is actually 2200 x 1125 lines. The space between active picture (1920*1080*10*2= 1.24Gb/s) and the total bandwidth (2200*1125*10*2= 1.485Gb/s) must have room for all metadata and audio, which it obviously does. 1920 x 1080p24 production format is .995Gb/s for active picture, and making that p60 raises the bar to 2.488Gb/s.
And of course, Mr. Luff is absolutely right. This is precisely the point. The theme of “1080p and Beyond” was to point out that broadcast production infrastructures will have difficulty supporting 1080 60p, while Digital Cinema production has already moved up to 2K and 4K production. So, the movie industry can create content in a format, 1080 60p or 2K, that broadcast production cannot.
Implementation of dual-link 3Gb/s distribution methods for 1080 60p would reduce the capacity of an existing HD infrastructure by 50 percent. SMPTE has issued 3Gb/s standards (424M, 425M) that can be used for intrafacility 1080 60p SDI distribution over a single coax cable. An alternate method could be to work in the compressed domain, with 1080 60p content compressed at 200Mb/s data rates or higher. This format could be distributed using SDTI, ASI or over the media network (TCP/IP). In this way, 1080 60p content will survive the editing and production process, and produce acceptable, artifact-free video.
Broadcasters are concerned with converting their production infrastructures to support 1080i (or 720p) HD content. Any thought of expanding production to 1080 60p or 2K is well out of mind. Mr. Luff’s observations support the article’s premise that the Digital Cinema industry may be the only source for true 1080 60p native format content.
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