[opendtv] Re: Digital vs. Analog Quality
- From: dan.grimes@xxxxxxxx
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 8 Jul 2008 08:56:39 -0700
I did a little more studying on the differences between the CECB converter
box output and the NTSC reception. For program material, I did find the
resolution to be better on the converter box (baseband composite output).
However, live material (i.e., news) still looked sharper and better on
NTSC. I am not sure why the live material on the ATSC looked softer.
But there were other differences that I noted that hampered the CECB:
Resolution: The CECB had better resolution than the NTSC. Details in the
lit areas seemed to be the same on both, but much sharper edges on CECB
output.
Noise: The CECB was much cleaner than the NTSC. The noise level was much
higher on the NTSC. However, the noise masked the compression artifacts
and dithered the inadequate quantization of the digital source.
Gamma: The gamma seemed much lower coming out of the CECB. The gamma on
the NTSC was much higher and created a much more natural picture.
Black Level: The CECB output a 0 IRE black level and there was a complete
lack of detail in the blacks. Even if the black level (brightness) was
raised on the monitor, detail could not be found in the blacks. I could
find no adjustments in the CECB to bring the detail back. However, the
NTSC did have black at 7.5 IRE and there was plenty of detail and
gradiation in the blacks. This suggests, to me, that the output of the
server is correct but the CECB box is not converting properly.
Delay: The CECB output was 3 to 8 seconds later than the NTSC. I could
watch an entire sequence of shots and switch to the ATSC and watch the
same exact sequence. I would hate to try and do a live call in show!
So now that I have studied the two pictures a little more, I can't say
which is better, just that each have their strengths. But overall, I am
obviously seeing the limitations of the CECB and not those within ATSC.
Please feel free to provide feedback if I am analyzing something wrong or
using the wrong terminology.
Dan
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