2012 State of the Union TECHNICAL comments - AVS Forum
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post #1 of 18 Old 01-24-2012, 06:20 PM - Thread Starter
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Not political comments.

Is anyone listening to CBS and hearing strange sounds (tones or "birdies") during the applause?

Edit: My wife just asked me, "Are they playing music?"
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post #2 of 18 Old 01-24-2012, 06:27 PM - Thread Starter
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So I changed channels. Fox is louder, (and no birdies.) ABC is quieter (and the applause is much quieter) and NBC is somewhere in the middle.

Note, this is in the New York market.
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post #3 of 18 Old 01-24-2012, 06:45 PM
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I'm watching on CBS on Comcast in Savannah, and I do hear the odd noise, but it has the best picture, so I'm sticking here.
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post #4 of 18 Old 01-24-2012, 07:21 PM
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One thing I have notice from the side shots is the light rays coming off of the TV lights appearing to look like spotlights.

Does anyone know which news organization was responsible for the pool feed this year?
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post #5 of 18 Old 01-24-2012, 07:39 PM
 
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I noticed that ABC had a twitter hashtag #SOTU the entire time.

Just completely embarrassing and unprofessional. I thought the hashtags were supposed to be for pimping the networks' own shows? Now they're pimping presidential speeches? Err?
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post #6 of 18 Old 01-24-2012, 08:08 PM
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Surfed around the HD channels with it on:

ABC
CBS
FOX
NBC
PBS
CNN
FOX News
FOX Business News
MSNBC

For whatever reason, NBC looked the best tonight.

'Better Living Through Modern, Expensive, Electronic Devices'

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post #7 of 18 Old 01-24-2012, 08:40 PM
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CBS looked DARK. Also heard the chirping and saw the spotlight effect on the wide shot from the President's right.
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post #8 of 18 Old 01-24-2012, 10:44 PM
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Here are screencaps. Audio on CBS was fine here and had the least delay. CNN seemed to look the best on my TV this year. Without question, Fox News was the absolute worst - it looked like a 480i upconvert.

CBS:


NBC:


ABC:


Fox:


My local PBS station:


Fox News Channel:


CNN:


MSNBC:


CNBC:
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post #9 of 18 Old 01-25-2012, 02:55 AM
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CNN always looks the best here. They finally got their HD house in order IMO.

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post #10 of 18 Old 01-25-2012, 06:14 AM - Thread Starter
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Quote:
Originally Posted by agus0103 View Post

Here are screencaps. Audio on CBS was fine here and had the least delay. CNN seemed to look the best on my TV this year. Without question, Fox News was the absolute worst - it looked like a 480i upconvert.

Nice comparison. Loading them all in my Win7 PC let me switch among them just by hovering the mouse over the thumbnails in the task bar. (I think it's called the "jumplist.") They look pretty similar, but yes, the Fox News image is the worst. Unless you captured the PBS feed when it was in between animations, the PBS logo was the most subtle -- to the point of not knowing it was there.

FNC aside, the similarity of the pictures is much better than it was in the analog TV days. I wish I could say the same about the audio. It sounded very different on the 4 or 5 channels I checked. This is no improvement from the analog TV days.

I remember doing a similar channel surfing experiment about a decade ago, when the DTV channels were fairly new. The loudness of each channel was sometimes different, but otherwise they all sounded the same. At the time, I attributed it to the DTV channel getting its audio directly from master control, before it went through all the processing that the analog transmitter used/needed.
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post #11 of 18 Old 01-26-2012, 04:28 PM
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The FOX News feed does look to be a 480i upconvert as evidenced by the stepping on the diagonals from the scaler:




The FOX network feed looks like a 1080i to 720p crossconvert as the diagonals are smooth:


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post #12 of 18 Old 01-26-2012, 04:51 PM
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Quote:
Originally Posted by hphase View Post

Unless you captured the PBS feed when it was in between animations, the PBS logo was the most subtle -- to the point of not knowing it was there.

The bug for this station has no animation, and what is shown is the normal transparency. The word "prime" is actually displayed between the big L and the PBS logo, but, against dark backgrounds, it's often impossible to see.

Unfortunately, as nice as the bug is, the overall picture quality of the station is typically just so-so, due to having five subchannels in addition to the main HD stream.
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post #13 of 18 Old 01-26-2012, 06:37 PM - Thread Starter
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Quote:
Originally Posted by agus0103 View Post

Unfortunately, as nice as the bug is, the overall picture quality of the station is typically just so-so, due to having five subchannels in addition to the main HD stream.

Not to mention that the main HD starts out at less than 19 Mbps and is decoded and re-encoded at a significantly lower bit rate to make room for the subchannels. Five subchannels?

Perhaps the HD is also scaled to 720P because 720p "compresses so much better"? Double
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post #14 of 18 Old 01-26-2012, 07:18 PM
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IMO, PBS went from first to worst. 19 Mbs would be adequate on most material with MPEG 4, particularly with 720p, but MPEG 2 is not enough.

As most viewers get their locals via cable and sat providers, it's time that stations start sending them dedicated MPEG 4 feeds. This could permit better than OTA quality. Cable stations already have this option. The downside could be that stations could add more streams to their OTA and then expect the provider to carry them all from direct feeds.
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post #15 of 18 Old 01-26-2012, 07:27 PM
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Quote:
Originally Posted by hphase View Post

Not to mention that the main HD starts out at less than 19 Mbps and is decoded and re-encoded at a significantly lower bit rate to make room for the subchannels. Five subchannels?

Yep, five subchannels, including one that is just an SD simulcast of the main HD channel. That said, even though quantity over quality is the motto here, the station's general manager, who is also the chief engineer, seems to be willing to listen to any concerns and, to my eyes, has done something in the last year or so to slightly improve the HD picture. I think average bitrates were shifted around a bit (HD averages 9 Mbps) and perhaps there were some encoder changes. Of course, the HD picture still isn't very comparable to the HD on the CBS O&O down the dial.

If I watched national PBS programs more often, I would probably get myself a FTA satellite system and take advantage of the 1080i stream that's available on the Ku band.
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post #16 of 18 Old 01-27-2012, 07:05 AM - Thread Starter
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Quote:
Originally Posted by TVOD View Post

IMO, PBS went from first to worst. 19 Mbs would be adequate on most material with MPEG 4, particularly with 720p, but MPEG 2 is not enough.

As most viewers get their locals via cable and sat providers, it's time that stations start sending them dedicated MPEG 4 feeds. This could permit better than OTA quality. Cable stations already have this option. The downside could be that stations could add more streams to their OTA and then expect the provider to carry them all from direct feeds.

Except for Fox (discussed later), all the other networks send much higher data rates than 19 Mbps which are intended to be decoded to "baseband" HD-SDI for re-encoding at 19 Mbit ATSC. I don't know for sure, but they all seem to use a mixture of MPEG4, MPEG2, and DVB-S2, but that's not really that important. It's the higher data rate that allows concatenation of codecs with minimal artifacts.

One generation of 19 Mbit ATSC is just adequate. Two generations of 19 Mbit ATSC is not adequate. Converting to 720p just generates more noise for the next encoder to waste bits trying to encode. Drop the data rate to 9 Mbps and I'm surprised it looks anything like HD.

Fox does the right thing by sending 19 Mbps BUT requiring stations to splice it directly to air, bypassing a generation of codec concatenation.

(Sorry to veer off topic, but it had to be said...)
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post #17 of 18 Old 01-27-2012, 05:04 PM
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Converting from 1080i to 720p may actually decrease noise for re-encoding as quantizing errors increase at higher frequencies due to larger coefficients in the quantizing matrix. The higher horizontal frequencies in the 1080i are filtered out for scaling from 1920 to 1280 pixels. Vertical conversion involves de-interlacing so motion compensation can be compromised from the lower frame to frame correlation. DCT blocks are larger onscreen in 720p which could make the block boundries more apparent. However, from empirical observation and from theoretical advantages of encoding efficiencies for progressive formats with twice the frame rate, conversion to 720p does appear to allow better results at lower bitrates. It's still the lesser of two evils and still not pretty.

ABC and NBC are using MPEG 4 for network distribution using Ericsson (Tandberg) encoders with phase-align audio for 5.1, CBS continues to use MPEG 2 at 40 Mbs with Dolby E for 5.1 using Harris encoders and FOX is now using Motorola encoders for the splicer system. Using a ratio of around 2:1 for cascaded encoding minimizes loss of downstream encoding efficiency from added noise, so as stated sending a network at ATSC bitrates of 19 Mbs is insufficient unless the stream itself is turned around directly for broadcast. While the splicer system does allow for efficient MPEG 2 network distribution at lower bitrates, it's not as efficient as using MPEG 4.

There seems to be a growing movement towards 1080/50p and perhaps 1080/60p. With the increased encoding efficiency of progressive formats, the extra bandwidth to carry twice the pixels requires far less than twice the bitrate, in fact some have stated it is nearly the same. On a live event such as the SOTU, it would be ideal as there would be minimal loss with conversion to 1080i and 720p. The downside to using 1080p (and 720p on some cameras) as compared to 1080i on live cameras would be the 50% loss of light sensitivity (1 stop) from not using the sensor row pixel grouping in interlace mode. Maybe by then 4k live production will be on the horizon and 1080p would be a moot point. Dual link 3G or single 6G, that should be interesting.
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post #18 of 18 Old 01-28-2012, 06:32 PM - Thread Starter
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Converting decoded 1080i to 720p introduces noise that is not in the original image. The next encode will waste bits trying to encode the added noise, resulting in either a higher bit rate or poorer image, depending on which parameter is being constrained. Any benefit of "encoding a progressive signal" is compromised by the added noise.
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