Your thoughts about PAL vs NTSC

[alenppc]

Originally Posted by pandy71

For me biggest limitation for 8VSB is low capacity - nett 19.3904Mbps - imagine MPEG-2 HD squeezed to 18.5Mbps... for H.264 is easier but not sure if aerial broadcast in US use H.264 (cable for sure).

H.264 coding was added later to the ATSC standard, but as far as I know it's actually not used at all, for compatibility reasons with early receivers.

However, thanks to some clever encoding techniques, today they are able to squeeze a very decent picture out of that single 6 mhz channel even using MPEG-2, it's pretty impressive. One of the stations I receive broadcasts two 1080i HD stations and two 480p stations over a single channel. The compression artifacts are only barely noticable with fast motion scenes but still not even close to the overcompressed garbage that cable companies sell, so the broadcast quality still beats cable.

[UberFreak]

As a long time collector of movies on VHS & LaserDisc, in both PAL & NTSC, in my opinion its a no-contest.

NTSC, especially from a composite source, looks absolutely terrible.
There is color-bleed, mostly inaccurate colors (compared to PAL), dot-crawl (unless a very expensive 3D Comb-Filter is used to separate luma & chroma), color sub-carrier leftover noise on luma, etc etc.

I always preferred PAL, when possible.

[pandy71]

Originally Posted by mc6809e

The first is just a student's report drawn from other sources. Nothing there really.

Intentionally switching from PAL/NTSC to multipath immunity in COFDM...
I have nothing against students reports btw - if they are correct and good sourced then fine for me...

Originally Posted by mc6809e

The second is a test of multipath, but at the smallest tested interval of 2 microseconds, the interfering path is still about 600 meters longer than the direct path! That's a bit large to test the theory behind the multipath resistance of OFDM (okay COFDM if you prefer) which is that the spacing of subcarriers allows for constructive and destructive interference, one compensating for each other.

To test that theory of the system, the path delays would have to be on the order of 1/818MHz which corresponds to 1.22ns. As a result of the long delays used in the test, what's being tested is not so much the multi-carrier aspect of the system, but the strength of the forward error correction. But it should be obvious what will happen for delays of 0.61ns+N*1.22ns -- destructive interference.

The third paper suffers from similar problems.

The fourth paper is worth looking at since it's a real world experiment.

In that paper 8VSB falls below DVB-T (8k) for impulse noise > 200 microseconds.

And for multipath the paper admits that the performance of DVB depends not on the multicarrier aspect of the system but on the forward error correction (and interestingly enough, 8VSB actually performs better in noisier environments than all other systems when the C/E is greater than 5 dB).

COFDM clearly outperform 8-VSB on some aspects, on some not - overall outcome is that 8-VSB provide better Eb/No and lower crest factor (and as such lower PAPR) where COFDM is better on mobile reception (and thanks to channel estimator it may deal better with multipath and seem that channel estimator allow to gain over 8-VSB significantly).
Both systems work in real life.