Fixin To Get Ready- A Geek-Fest
I mentioned in a previous post I have been in high gear getting ready for the Olympics. One major issue I have been working on is balancing the bitrates between my main HD and Universal Sports. I have not applied any changes on air yet, and found an interesting software bug that will be resolved today.
The DTV streams are controlled by a server that allocates the bits for each encoder during the process of muxing the streams. To describe the system, the three encoders take our serial digital video and audio inputs and combines them into an MPEG-2 stream, which are fed into a unit that combines them into one output stream. That process is called the mux, or multiplexer. It combines the encoders and PSIP information into one output stream.
It also gives a feedback stream to the encoder that tells it there are basically 19.4 Million bits available, and that each stream needs a certain amount to provice a good quality picture. It determines that if HD has high action and lots of detail, the encoder should use the maximum allotment of bits to encode the streams to MPEG-2, using spare bits from the other streams. It also tells the encoder that if the pictures are simple with little motion, to give the extra bits to the sub-channels.
That’s the Statistical Multiplexing system in a nutshell. The streams’ bitrates vary according to the demand of the streams. Its’ goal is to deliver the most efficient use of the total number of bits on the output. If the streams do not require all the bits available, it adds the null packets I showed you in the “Air Versus Cable” posts to ensure the output stream is always 19.4 Mbs.
As I mentioned in a previous post, I am squeezing every bit for active video I can use without adding null packets and especially without over-subscribing the data available. That’s commonly referred to as being bit starved- trying to get say 20 Mbs with a cap of 19.4 Mbs available. Every receiver seeing that situation would croak, freeze, and possibly lock up and have to be re-booted, so it’s a situation we try not to introduce.
Another goal I have is allowing the AFD signal to pass from the network. The Active Field Descriptor tells your receiver how to display the 16:9 picture on your 4:3 set, or allows cable and satellite to deliver the proper ratio. We have been working with Time-Warner Cable and our encoder manufacturer and have discovered a software issue that needs to be addressed.
So today, I will be upgrading the server software and applying a bug patch to fix the AFD issue, and help smooth out the datarates and improve the MPEG compression. The main server was upgraded with only a little interruption to the sub-channels.
There will be little noticeable impact on the air for the main HD, although I may have to bring the sub-channels down while new code is flashed into their memories. That’s the kind of thing I’ll do at a time that will have little impact on you viewers. It takes 10 to 20 minutes to download the code into each encoder, which takes it off air during the process, but I’d rather do it now than to wait. Don’t panic if we disappear today around noon, we’ll be right back! To quote Col. Mustard in “Clue” “This is war, Peacock. Casualties are inevitable. You can not make an omelet without breaking eggs, every cook will tell you that”
UPDATE!
I’ll flash the encoders in the middle of the night when everyone is sleeping, so keep checking here for an advance notice of when it will happen, but for now everything is running nicely, and I was able to increase the bitrates more than I anticipated!
The firmware was flashed into the encoder Saturday morning between 3 AM and 3:30 AM. We are set with the latest software!
Sunday Morning Snow In Wendell
Here’s my puppy Zeus playing in the snow Sunday morning.
Air Versus Cable Part 2
In the last post, we looked at the 8-VSB RF signals and discussed data rates on the DTV streams. This time we take a look at QAM used by the cable industry. I captured the screen shots on my Sencore 1850 MPEG analyzer on the same day for air and cable. Here’s a look at Time-Warner Cable’s QAM 256 for our channels:
You can see in the upper right block, instead of 8 lines of dots, you have 16 clusters of dots across, and 16 down. That is representing QAM 256 and is named so because 16 times 16 is 256. Instead of having 19.4 million bits per second bandwidth, QAM 256 has 38,800 million bits per second. Man! I’d love to have that bandwidth over the air! With a wider bandwidth, cable can insert many more channels into a single standard channel, which is pretty efficient use of their system. More than one network can occupy a single QAM channel, and it can provide many SD channels.
In the above picture, you can see the null packets are taking upmore data than I am sending over the air. The data rates for the three channels are pretty much the same as I am sending out. The unused data being occupied by the null packets will eventually be used by another channel. They can place several SD channels in that space, or a combination of HD and SD. In their master PSIP table, all they have to do is assign the PID numbers, and it will then show up on the system.
One argument we hear a lot is about providers compressing the broadcast signals even more than over the air. The captures in this and the previous post were taken moments apart. Naturally, the bit rate varies due to the complexities of the video, but the captures from off air and cable were pretty close to the same. It’s hard to get an apples to apples comparison, but there’s really no need for the cable ops to re-compress the signals at all.
The biggest difference is in the CVCT tables, which is smaller than the heavy error correction I send over the air in my TVCT tables. They do not have to worry with many of the issues a broadcast signal has to deal with since their system is a closed system, meaning the cable is shielded from the outside world.
By the way, you can click on any of these pictures to see the full frame version on your browser for clarity.
If there’s anything you’d like to see, let me know. Post a comment and I’ll see what I can do.
Air Versus Cable Part 1
I want to take a few minutes to talk about invisible signals in the air, and in part 2, what QAM looks like. It’s impossible to “see” RF signals with the naked eye, so we rely on test equipment to show us what is going on in the high speed RF spectrum. You may know by now TV stations in the United States use a system called 8-VSB to deliver digital TV to you homes. Each channel can use around 19.4 million bits per second to deliver digital TV to your home. I have some screen captures from my Sencore 1850 MPEG analyzer that shows you what the signal looks like.
This is a representation of the 8-VSB signal. The yellow dots on the black square in the upper right hand corner shows the carriers lined up in 8 columns. Each one of those dots should line up fairly straight, in order for your receiver to decode the signals contained there. The squiggles in the bottom right corner displays the mathematical relationships the carriers have to each other. If anything gets out of line, the receiver can’t lock onto the signal enough to decode whats contained in it. When the signal bounces off a building, tree, or other object, it will have an affect on this signal, either adding or subtracting to the main signal. The receiver can get confused if any of these carriers get sloppy, and aren’t in a close line with the others. Remember, there’s a lot more data contained in the signal than just video and audio. There’s many tables and error correction bits sent to ensure the receiver has the best opportunity to decode the signal.
Above is an overall view of the tables that make up an over the air DTV signal.
Here you can see a chart of the actual bitrates on the air. The top bar on the graph is for null packets, These are basically empty packets of data to fill in the full bandwidth allotted. As you can see, I am not wasting very many bits on these things, and have most of my resources allocated to the main streams. The second bar shows how much the data tables take up.
Our HD stream is running at 14.35 million bits per second and is taking up almost 74% of my bandwidth. Universal Sports is running at 3.1 million bits per second, and Weather Plus is only slightly over 1 million since it is mainly still graphics with little motion.
Now this is our reference, or non Olympic bitrates. (You should have known I was going to mention the Olympics eventually)
In years past, we have shut down the Weather Sub Channel and throttled down the second channel to the bare minimum.
This time, Universal Sports will be carrying many live events, so I have to crank up the bitrate for it as high as I can. We just installed a new receiver for Universal Sports, so we able to capture the full bandwidth they are sending on the satellite, which is just under 5 million bits per second. However, to get 2 more megabits, I have to steal it from somewhere else, or one of my other channels. I can get about half a million from the Weather Plus channel, and pull another 1.5 million from the main HD channel.
Naturally, I don’t want to reduce the HD bandwidth any more than I have to. The less bits you have, the more compression you have to do. In a high speed sporting event, that can be less than desirable.
The system uses statistical multiplexing, which means the streams can be shared in a pool, and bits are assigned to the stream that needs it the most. That way, when one channel has a scene with little motion, the extra bits can be used on the higher motion stream. In other words, the HD will always have top priority, and get all the spare bits required to deliver the best picture from the other channels which may not have a high demand for bits. The other channels get what is left over, which will still render a good picture.
I will be changing the bitrates very close to the Olympics. The Opening Ceremonies are amazing to see and use every amount of detail the cameras can capture. If you’ve never seen the Opening Ceremonies in HD before, you are in for a real treat!
Time To Get Ready For The Olympics!
cLeaR QaM on TimE-WarNer
For a complete list of clear QAM channels on Time-Warner in our area visit the list maintained by Erik Garci at http://home.roadrunner.com/~res18h39/channels.htm
A couple of weeks after Time-Warner moved NBC 17 to a new channel in late November, the emails had died down so I figured everyone had resolved the issue of missing the NBC 17 digital channels by rescanning. The emails started back up recently, as well as calls to our digital hotline and keyword searches on this blog.
If you are still missing WNCN digitals on your basic cable, simply re-scan the channels or in the add/delete channels menu, you can manually add channel 93-2 and the TV will revert to displaying it as 17-1, 2 & 3.
We have also received some wild reports of their customer service reps advising more expensive options, etc. Even as far as saying they do not supply “dash channels”.
I have contacted and spoken to their Director of Customer Care Center for our area, and he has made sure they are giving out the correct information that just a simple re-scan will bring things back to normal.
(We had a long talk this afternoon.)
Today, a viewer sent us a very distressing email from a TWC rep, that made several wrong statements, and naturally I forwarded it to TWC to investigate. While I am no expert on cable systems, or call centers for that matter, I assumed we had covered all the bases having a dialog with the local call center. It turns out that TWC also offers email support and real-time chat options, that are handled by other divisions and subbed to vendors, so they did not get the message. In periods of high call volume, they can even roll some calls over to Wilmington or Charlotte’s call centers.
They are aggressively trying to get all the centers coordinated to give out the correct information. The customers affected are basic or broadcast cable subscribers and those that are connected directly to cable without a set top box from the cable company.
There is no requirement or mandate that forces them to provide digital service on this tier, but TWC has allowed the local channels on this package as an added value to their customers with digital cable ready sets. That is, sets with the cable QAM enabled tuner can decode the local station’s digital signals at no extra charge connected to basic cable.
Not all cable systems do this, nor would even allow this, but our local systems saw it as a good idea 10 years ago, and I have to agree it has been an excellent gesture by them. It’s an unadvertised feature, but once you connect your TV to it, it finds the local digital signals for you, and displays the stations by their over the air channel number identification. Many viewers may not even know it did it, until it goes missing.
Cable started off as pure analog signals, and has added channels and new technologies. They are just trying to shuffle the channels around so that the different blocks of services are grouped together to help make it more manageable. Certainly, having an all digital cable system is desirable, but there’s still a huge number of analog sets out there, so the system is still hybrid analog and digital, and may continue that way for many more years, so now is a good time for them to get their channels organized as new services are rolling out.
I read on the local avs forum that some viewers are missing WLFL’s digital. This is probably an easy fix by swapping out the filter at the home. From what I have read, they are very close to the filter’s cut-off point, and if the filter is a little sloppy, it may be knocking them out also. Call them to have a tech check into it, as all the local channels should be free, open, and clear on the local TWC systems equally.
As a final thought, keep in mind you are paying them for service. It’s your right to call them when something is not right. I have a few contacts with them and the satellite systems, but you have the right to receive the service you are paying for, so you should call them when things aren’t quite right. Don’t be bashful! They tell me they receive around 10,000 calls a day and double that many at times. Keep after them until your issue is resolved. That’s part of what you are paying for!
Troubleshooting Antenna Issues
Tips on troubleshooting antenna issues from a couple of animated friends of mine.
Esse Quam Videri
To be, rather than to seem. That’s our state motto and a pretty good analogy of digital technology in our homes today. Some readers think that because they have been watching an HD set for years, that everyone is also watching on HD sets. It took color TV sets 10 years to become popular, and almost 20 years to become the standard in homes.
Digital seems to be running far ahead of the color TV transition, but still has a way to go before it is the dominant display format in homes without using a converter box. The price of today’s sets are now inline with what we’re used to paying, and the availability of actual HD programming is gaining, but still not where it needs to be, just like color programming lagged behind consumer’s desires in the Sixties. It’s all catching up, but still, not as fast as we seem to think it should be.
I openly admit, that I watch a ton of streaming video on the Internet. I want a huge central storage drive array accessible by all my TV sets and computers. I want a Roku box to watch streaming video on my TV, even though it could put me (broadcasting) out of business very soon. It seems like the number of people watching video on the Internet is very low. Most shows are lucky to have 500 viewers at a time on the Internet.
As broadband gets faster, we seem to think everyone has broadband, rather than the huge number of dial-up connections still active today. I could not imagine going back to a 56K modem that connects at 33K if the wind is blowing right, but that is reality for a lot of computer users who get on, read email, and log off.
As I told one viewer in an email response, I was hoping the Christmas buying season would propel the number of HD sets and bring them closer to “the norm” in homes. Although my family did their part, the economy didn’t help out a lot, but their are bargains out there to be had. If you didn’t get one from Santa, I encourage you to go out and get one now while the price war is in full swing.
It does not really matter that much where you buy, just buy! Wal-Mart and Target have been very competitive this year on pricing, and CompUSA on Capital Blvd. surprised the heck out of me with knowledgeable, friendly, helpful customer service, and HH Gregg was close behind. As for Best Buy, what has happened to you guys since Circuit City closed their doors? You used to be my “happy place”, and I would have spent all day there if you had a Geek Cafe’ to feed me while visiting. I wasn’t impressed this year. Put a Starbucks or Subway in that wasted space to right of the front door! (and drop some prices, please!)
In the program provider category, you can use an antenna, cable or satellite to receive your signals. The cable and satellite providers seem to deliver signals to your TV, computers and provide support. I am not associated with any of those providers, and have little influence on them except to request them to investigate service issues you report to us. You are paying them to deliver your signals, and therefore you have more control of their service than I do. If you can’t get a resolution from your cable provider, contact your town hall who controls the franchise agreement with them. Ask anyone in Wilson how they like their service!
As for HD news, we are once again pushing to convert early next year. It’s an expensive investment in equipment that the economy just didn’t allow us to spend last year,nor the year before, but we are hopeful to convert early next year. I doubt we’ll be able to do it before the Olympics, but we hope to go at least widescreen 480i in the first quarter. Our current studio cameras just don’t look good in 16:9 and we have to replace them first. Our news set takes 6 cameras to cover all the angles, where other newscasts only need 3 or 4, so we have a huge investment to make just in cameras. In the meantime, we are trying to keep the content relevant and not waste your time with flash, smoke and mirrors.
So to wrap up this Holiday season, get out there and buy an HD set. Shop around for your program providers and switch if you’re not happy. Home entertainment should not be stressful!
Happy Boxing Day
Actually, in my case it’s un-boxing day since I have to get to installing the toys Santa left me. I did not plan to make this Christmas a high tech digital event, but it turned out that way.
On the giving side, I try to ensure any high tech gifts I give the family is user friendly enough for them to use. Since Mom has mastered the converter box and myriad of remotes, I figured she could easily move up to a flat panel TV. She absolutely loved going from her 25″ console to a nice 32″ flat panel with one remote to control everything.
I also didn’t expect my sister to end up with a 42″ from her family. Only a simple question of how to scan channels and connect the Dish Network receiver on the phone, and she was ready to go.
All I asked Santa for was a new radio for my car, since the CD is broken and only ejects the disks continuously. Now, buying electronics for an engineer is not advisable, I did show Santa that I needed a front USB connector and an auxiliary audio input for my peripheral gadgets. I wasn’t expecting the HD radio, 8 Gig SD card slot, and XM radio! That is super cool, and I can’t wait to get it installed today as soon as the yard dries up a little.
My best friend got lost on the back roads between Clayton and Knightdale a few nights ago when we tried to meet up to finish some last minute shopping. I ended up getting him a GPS to relieve some of the stress of getting lost.
So, all in all, I ended up giving and getting what was on most people’s shopping list: flat screen TV, GPS, car electronics, etc. It turned out to be a high tech Christmas, even though it was all last minute and unplanned!
So, how did you fare this year? Did you get everything you wanted? Are you in line now getting exactly what you wanted with that gift card? (This is the first year I have not received a Best Buy Gift Card!)
Leave a comment and let us know how your holiday went!
A Merry Digital Christmas
Being an Engineer, I am always curious how things work. While setting up the technical logistics for Wes’ weather reports from Crabtree Valley Mall here in Raliegh, I had a few minutes to talk to Santa as he took a break to see if we could clear up a few things.
Not everyone believes in Santa, and there’s a lot of Scrooges out there. Foreclosures and homelessness has reached record levels this year, and it’s doubtful the bankers like Scrooge will let a little holiday get in their way of kicking hard working families into the streets.
So I asked Santa what we can do to get into the spirit and find the magic in these troubling times. “Believe in miracles, and they will happen”, he said with a twinkle in his eye. I’m pretty sure there’s a difference between wishing for a miracle, and believing in them, so I think his advice is pretty good.
There’s a website that tries to scientifically dispute Santa’s abilities stating the lead reindeer would melt from the enormous speed required to make the trip. But I think I have things figured out!
As a child, I noticed all my toys had a shipping label to Sears Roebuck & Co. In Greensboro. I also wondered why the boxes were always opened, and batteries were installed. None of the toys I bought ever had the batteries in them. I did wonder why he used the cheaper Ray-o-vac batteries in stead of EverReady batteries which had a little more power, but I was always thankful he took the time to let me get a few hours of play out of it.
In order to load the sleigh with enough toys for all the world’s children, it would have to be huge. I figured out that Santa used Sears as a pick-up point to distribute the toys in this area. He’d deliver a batch, then return to Greensboro and re-stock. I’m sure those folks that had to work Christmas Eve felt special they were working for the man, Santa.
One year my cousin Mike and I got walkie-talkies, but one of mine had a bent antenna. It turns out that Santa sent them to my Dad to test to see if they had enough range to reach the two miles between our houses allowing us to talk to each other. Unfortunately, while Dad was testing them, he was parked beside the road, and as a car came by, he closed the door on the antenna. Not a big deal, since I had two, and Mike had two, we could still talk.
Santa admitted he still uses the manual data entry for the “naughty and nice list” and I told him there’s hundreds of programmers out in RTP that would love to help him develop an electronic database that he could easily search, sort, and swap naughty kids to the good list with one mouse click. Entering all that data would be the hard part, but he said the Elves could handle that with a few cookies and milk.
We also talked about digital TV’s, and how most electronics were getting smaller and lighter. He said he was very happy that this year most folks are looking smaller secondary HDTV sets for bedrooms and kitchens. I bet you didn’t know that’s why there’s a Best Buy located near every Mall. That’s his depot for deliveries of electronics. Likewise, there’s a Apple Store, Dell kiosk, and camera store at each mall! That database would help him tremendously in keeping track of these depots.
Fortunately, this is the season of good will toward men. The time you put aside your prejudices, and practice patience. Long lines at the check-out is a good time to look at the person next to you, shrug your shoulders, and smile. Just a smile is all it takes to make someone else feel better, knowing that someone else feels the same as you.
Have you found you have lost TV signals that were just fine last year? (I’m smiling and shrugging my shoulders) It happens, but keep in mind that not all stations are on the same channel as last year. My station was acually on channel 55 last year. This year we are on 17. The trees affect antennas a little differently in the Fall, and remember the atmosphere is moist and a bit lower this time of year. That’s why signals skip a bit differently off the outer atmosphere. Heat rises, but when it’s cold outside, there’s not a lot of heat rising.
I can’t predict what affects Santa’s sleigh might have on your TV reception, but if he bumps it on the way down the chimney, or a reindeer accidentally kicks the antenna mast, you may have to re-aim the antenna on Christmas morning as well as after the cold winds of Winter settle in.
Hopefully, once the weather settles into Winter, reception issues will be a thing of the past. Cable will work as expected, and we’ll all have a good night.
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