Wither HEVC Part 3

In our previous blog, we raised the problem of the relative rates of:

1. bitrate reduction, due to new generations of compression technology

vs.

2. bitrate proliferation, due to the introduction of higher-resolution broadcast standards

We can easily quantify this problem with a little simple math. Let’s start in 1994, with the introduction of MPEG-2, the original digital compression standard developed for broadcast technology. Let’s set 1994 MPEG-2 compression technology to 1 and, likewise, set 1994 720 x 480 SD resolution formats at 1. For present purposes, we can assume these two forces are roughly balanced: that is to say, MPEG-2 compression technology successfully reduces the bits generated by digital 720 x 480 SD formats to manageable levels for practical purposes of transmission and storage.

Given this 1 to 1 parity between SD formats and MPEG-2 compression, as long as SD formats continued to dominate TV broadcasting, there was no great practical urgency about developing better encoding technology. And, in fact, although better H.264/AVC (MPEG-4) compression technology became available as early as 2003, there was little interest among broadcasters in the new technology over the next several years – despite its ability to cut SD bitrates in half.

Widespread interest in better H.264/MPEG-4 compression technology only began to develop among broadcasters after 2007, when the replacement of 720 x 480 SD formats by 6X larger 1920 x 1080 HD formats first become common. But, while the flood of bits generated by HD formats made the inefficiency of older MPEG-2 compression patently obvious, even after broadcasters switched to next-generation H.264 compression, the bottom line was not a return to the old 1 to 1 (SD to MPEG-2) parity of 1994. Instead, with a 6X increase in bits due to new HD formats, balanced by a 2X reduction in bitrates from H.264 compression, the new HD to MPEG-4 parity level was reestablished at 3 to 1.

The industry now faces the prospect of a second transition to a new 2X better level of compression technology with H.265/HEVC (MPEG-5).  Although adoption of MPEG-5 for HD formats would practically restore the old 1994 parity level (1.5 to 1 vs 1 to 1), just as adoption of MPEG-4 technology waited on the spread of new, higher resolution HD picture formats, significant take-up of MPEG-5 compression is likely to wait on widespread adoption of the new 4X larger 3940 x 2160 4K picture format. With 4K formats, the bottom line will not be something closer to 1994 parity levels, but rather something substantially worse than current levels, with a 6 to 1 ratio of 4K bits to MPEG-5 compression capabilities.

Future developments seem more likely to continue this progressively worsening trend than to succeed in reversing or even slowing it. Projecting forward to a new 2X better level of compression technology with a future H.266/MPEG-6 step, this advance in bitrate reduction seems certain to be more than offset by a yet another 4X larger resolution step: the 7880 x 4320 8K picture format.   In the 2020s, then, the bottom line is likely to be a 12 to 1 ratio of bits to compression capabilities, measured by 1994 standards.

Is this decade-by-decade slide in bit ratio, from 1 to 1 in the 1990s, to 3 to 1 in the 2000s, to 6 to 1 in the 2010s, to 12 to 1 in the 2020s, a worry? And if it is not something we should worry about, then why not? That will be the subject of our next blog.

Wither HEVC?

The H.265/HEVC or MPEG-5 encoding standard (finalized in 2013) is the next generation of encoding technology after the H.264/AVC or MPEG-4 standard (finalized in 2003). Just as AVC stands for Advanced Video Coding, HEVC is an acronym for High Efficiency Video Coding. The 5^th generation number associated with the H.265 and MPEG-5 labels is somewhat misleading since, in fact, HEVC is only the third generation of MPEG digital compression technology developed for broadcast television. The initial MPEG-1 standard (finalized in 1991) was targeted to low-resolution video CD formats, while work on an MPEG-3 standard, intended to support HD TV formats, was abandoned after a year or so in favor of a relatively minor extension to the original broadcast TV standard, MPEG-2 (finalized in 1994).

Compared to other areas of high technology—e.g., semiconductors, where “Moore’s Law” predicts capabilities will double every 2 years—the decade-per-standard rate of advance for digital compression is surprisingly sedate. This relatively slow pace results from two major factors. One factor is a law of diminishing returns that governs all forms of compression: namely, every unit of reduction achieved makes it harder to achieve the next unit until, when some theoretical minimum is reached, infinite force must be applied to make any further gains.

The second factor is the fact that, practically speaking, adoption of a new, more efficient broadcast compression technology is tied to the adoption of a new, higher resolution broadcast standard. For example, the original MPEG-2 broadcast standard was designed to adequately support the transmission of SD video formats over available transmission pathways. Although next-generation H.264/AVC (MPEG-4) encoders were able to cut MPEG-2 bitrates in half with no loss of video quality, their appeal was nonetheless limited when they started to appear following completion of the 2003 standard. Older MPEG-2 encoders were still adequate for SD, and both more mature and less costly than the latest high-powered H.264/AVC encoders.

As a consequence, widespread adoption of H.264/AVC encoders had to wait on the spread of HDTV programming, which literally overwhelmed MPEG-2 technology by multiplying SD picture data by a factor of 6X. HDTV programming, in turn, naturally lagged behind the adoption of HDTV sets. Since HDTV sets did not reach critical mass in the USA until 2006 (when they finally passed 10% of the installed base and sales figures started climbing rapidly), broadcasters did not begin buying H.264 encoders in any significant numbers before 2008.

There is a lot to be said on this topic and we'll continue it more in our next post with information about adoption of H.256/AVC encoding. To learn more about Telarity and our video compressors, visit our website. We are also active on Twitter and LinkedIn publishing company updates and industry news.