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This is a sub-selection from But how lossy?


MovieLover76

join:2009-09-11
kudos:1
reply to SunnyD

Re: But how lossy?

HDTV quality is what it is at the moment ATSC HDTV is a set standard, some providers like FiOS don't recompress it, some cable operators compress it really bad, hopefully for normal HDTV if they deployed H.265 video they'd keep the bit rate the same and increase the quality, this could help streaming sevices like netflix whose HD streaming is even worse.

Their's no point in going up to 4K, if they don't keep the bitrate high, much higher than blu-ray.
I myself would actually be happier to see this improved compression to current 1080P HD like streaming and HDTV.
instead of 4K. Eventually 4K will come, but their is no rush as even the sets are like 25K

cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9

ATSC HDTV is a set standard

In so much as it's a 19Mbps stream, yes. However, the broadcaster can do what ever they wish in that space... one high rate HD stream, one lower rate HD and two SD's, etc. FCC rules prohibit cable systems from modifying OTA broadcasts -- they have to broadcast what they're handed. (the broadcaster can hand them a different stream than their transmitter, and that's ok. PBS does that around here.) And ATSC (8VSB) is MPEG-2, and so's the US cable network.

Skippy25

join:2000-09-13
Hazelwood, MO
There is an entire website dedicated to keeping track of the compression/bit rate being used by DirecTV and it will show you what shows are being shown at what rate.

I dont recall what it is, but I am sure your friend Google can find it for you.

cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9
I wasn't talking about DISH and/or Directv -- who use MPEG-4 and various patented variable field compression Magic(tm) to reduce the bit rate even more. Or Uverse who use low bitrates and smoothing (aka "blurring") to reduce their bandwidth. (if all you watch is Uverse, you won't notice it.)

I was talking about ATSC (over-the-air) and CABLE broadcasts -- which are MPEG-2, still.


Guspaz
Guspaz
Premium,MVM
join:2001-11-05
Montreal, QC
kudos:23

1 recommendation

reply to MovieLover76
4K can be done at less than Blu-Ray bitrates. ATSC broadcasts are roughly 18.3 Mbps after overhead is taken into account, and that's typically MPEG-2. h.265 can produce the same perceptual quality (measured by PSNR) at about 5.5 Mbps. If you go for a simple quadrupling of bitrate to account for the quadrupling of pixels, you'd get equivalent ATSC quality (pixel for pixel) for 4K video at about 22 Mbps.

In practice, however, bitrate and pixel counts don't scale in lockstep like that. If you double the number of pixels, you don't need to double the bitrate. There are a variety of reasons for that. For one thing, as resolution increases, the compression artifacts shrink (in real-world size, not pixel-size), making it harder to discern them. For another thing, there's only so much detail in an image, and resolving a low-detail area in higher resolution might not require any extra bits at all.

I don't have any numbers to say what the reduction would be... but in any case, the point is that decent looking 4K video can be done at substantially lower bitrates than blu-ray supports. Of course, in practice, blu-ray movies use substantially lower bitrates than blu-ray supports anyhow, so I suspect it would come out in the wash.
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djrobx
Premium
join:2000-05-31
Valencia, CA
kudos:2
Reviews:
·Time Warner Cable
·VOIPO
reply to MovieLover76
said by MovieLover76:

HDTV quality is what it is at the moment ATSC HDTV is a set standard, some providers like FiOS don't recompress it, some cable operators compress it really bad, hopefully for normal HDTV if they deployed H.265 video they'd keep the bit rate the same and increase the quality, this could help streaming sevices like netflix whose HD streaming is even worse.

TFA suggests that H.265 produces equivalent video to H.264 in 50% of the bandwidth. As we know, lossy codecs are highly dependent on perception.

That begs the question - how does H.265 work? What was removed to gain such compression? And is H.265 at 50% truly equivalent to H.264? When you work with compression tools you'll often see things like "DVD quality", "CD quality", and the results are never anywhere close to those things.

Perception is tricky. If the people who created H.265 want to look good on paper, they'll survey a bunch of non-technical people, sit them in front of a 27" HDTV, 10 feet away, and ask them if they can notice a difference or not.

The scariest thing I ever saw was a poll about the sound quality of Sirius satellite radio (sorry, I've long forgotten where it was, I think it was a car enthusiast forum). There were at least 100 response. 50% thought it was as good as CD quality. 5% thought it was BETTER than CD quality!
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