Hackaday Prize Entry: Adblock For TV

Contact, the 1985 book by Carl Sagan, was significantly better than the movie. Five people went through the wormhole, three machines were made (in Russia, Wyoming, and a third on Hokkaido), Erbium did something, and the novelization provided much better worldbuilding. One of the more interesting characters in the book was H.R. Haddon, the megalomaniacal business man, made his first million designing a chip that would block advertisements on TV. The book strongly suggests this commercial-blocking chip was a purely analog device, a concept that would have been an amazing abuse of NTSC produced by a damn fine engineer.

Now, even though cord cutting is commonplace and streaming is taking over, there’s still commercials on Hulu. In a few months, I’ll have to pay $5 a month to watch Star Trek with commercials. There is obviously a market for ‘adblock for TV’, and that’s what [PixJuan] is doing for his Hackaday Prize entry.

[Juan]’s device is a basically an HDMI switch with a remote that’s pressed every time the ads start to show on a broadcast. This switch will change the input of the HDMI switch from a cable box to a Raspberry Pi and play a short video clip or something else that isn’t selling you crap. When the Raspi is done, the switch goes back over to the original input.

With a bit of computation in this adblock-for-TV device, there are a few more options for ad detection. The Raspberry Pi could build a database of when ads play and for how long, depending on the channel. This is a great project that has a lot of potential to use some interesting techniques like computer vision and machine learning for the goal of removing commercials before they start.

93 thoughts on “Hackaday Prize Entry: Adblock For TV

  1. I’m sure if you were using a DVB source you could read the sub-titles. It’s been a while since i checked, but I notice ads didn’t have sub-titles…might be an option. Another is often to check the sound levels…constant wall of noise for 30+ seconds is likely an ad. Another option might be to monitor for the station logo and when it has gone for more than a few seconds, then you might know you’re seeing commercials. Or a combination of all the above.

    There’s also other apps which strip ads from recordings automatically, perhaps their algorithims could be adopted for real-time use?

    1. I was just wondering about other ways to spot the transition and rather than trying to tell the difference between ad and tv programme, one could look for the usual few frames that designate the change between the programme and the commercials.
      Most of the tv programmes I can think of, tend to have the same short reel (say a freeze-frame or short clip that identifies either the station, the programme or the sponsor for the programme) when moving from the programme to the adverts or vice-versa. When one detects the button press (from the watcher) to say that the start of adverts has begun, you sample one (or more) frames of the live video and then await it to be repeated again (on the grounds that the same images will be seen on the transition back at the end of the commercial break).

    2. Look for the channel bug, that little logo usually in the bottom right of the screen. Prior to commercials, most networks have it change, either becoming opaque, or moving and then disappearing.

      I don’t use hulu often, so I’m not sure what they have that is similar. I recall that when I watched free hulu stuff the progress bar would have yellow markers where ads would occur. Perhaps the length of the show plus some machine learning could divine a useful pattern

        1. Or use a tiny tripod on a tiny webcam near TV set screen. Then run JavaScript Resemble.js to compare snaphot images of the channel bug. When the image is 90% or more then it is still there even with background changes. But if it is 20% to zero it must be gone, so now mute the video through your laptop. Un-mute when the percentages are arbitrarily high. Bug must be back. You’d have to reprogram it for every TV show though. Not a biggie as you could make reprogramming automated.

          1. RobM – I understand what you mean by SNR (signal to noise ratio) in where the translucent bug logo has background video activity going on behind it adding to the video noise floor. That’s where Resemble.Js does well. Instead of triggering off of a 100% match, it returns a percentage of the likelihood of a match from the template you took during the adhoc setup phase. You just experimentally figure out what percentage range like 90~100% match range (or even lower). When it disappears totally for a commercial break, it is likely that you get a return of 0% (roughly as advert may return mid-range falsing in the 10~50% range). That’s when you mute the audio or mask it with another audio source. Leave the video alone so you can do a manual over-ride if the system chokes. It’s the advert’s annoying audio that insults your intelligence.

          2. I’ve noticed that on American TV the bug or logo is very translucent with background video noise. It’s either in right or left corner and it can intermittently be blocked by 5-seconds of other pop-ups which might cause a false triggering if you don’t put in a 5-second delay on advert triggering (means you’ll get 5-sconds of advert and miss 5-seconds of desired TV show on returning). My idea to use an adjustable camera may prove to be superior to porting the video through a PC for electronic image analysis as it tends to not find the logo too well – like in that ComKill app mentioned in this thread somewhere – BTW a very cool advert killer app!

            To enhance a camera based system, you would need edge detection like [RobM] said. However, how can you do it without electronics, i.e. manually? You could make DIY camera photo dodge out of two black paper cards with a rectangular holes in them, or use a small manually adjustable camera iris mechanism to limit the side light from the video’s screen allowing the camera to just focus on the logo and nothing else (SNR?).

            Enter the Joseph-Joseph Spaghetti Measuring device – https://goo.gl/B4WcPR – It has 4 iris settings which can be modified by breaking it apart – and only costs $4 – USD!!! All you need to do is glue or press fit it to a wooden mount on the camera’s front. The camera may block your viewing the TV set but the goose neck version I’m recommending can be offset to the side of the TV and suction-cupped on the TV stand. Set the app to take a picture every 1~2 seconds and RESEMBLE.JS compares it against the template photo you took at beginning of your TV show or movie. A 80~90% match means HIT. The iris can be used to filter out the CNN logo’s moving time-stamp below the acronym CNN. Also DISCOVERY channel has a spinning globe which could be filtered out too.

            You may need a advert mute manual over-ride on the PC’s laptop. As the TV networks do crazy things with the logos and false triggering will occur periodically. But it’s still a basically good idea to kill commercials.

    1. I used to have a PC running MythTV that did a pretty damn good job of it. I think it used blank frame and watermark detection (possibly among other tricks like “average volume level”?).

      It had the luxury of doing it post recording though, rather than real time.

      But you’ve given me a good idea for an FPGA project :)

      1. Yes! Mythtv is Awesome, I ran mythtv for years on my cable before the digital blackout. I did notice right there at the end, that with a much faster rig than what I started with, mythtv could detect commercials in the whole file in litteral seconds. This over the whole recorded file, post processing on disk. So I think with a fast enough cpu and big enough memory block to scan, real time detection should more than possible.

  2. I had a similar idea about 20 years ago, when DSP, Computer Vision and AI Learning were more of a wish then a technology. The simplest way to detect commercial was to look at the sound level. The sound during commercials is usually much louder.

    Then, I suddenly realized the best way to remove ads from TV: don’t watch TV. At all.

    Since then, not only I don’t watch TV any more, but I don’t even own a TV. You never realize how much of a waste is TV watching, until you remove it completely. Your life will dramatically change in a good way. You will see the world with different eyes. You will start living your own life, instead of living someone else’s fears.

    Not kidding. Mass-Media is creating a fake reality bubble, a bad one. Even if you know it’s fake and distorted, it will still affects you in the long run.

    Just try a few months without TV. You will never ever want to go back again.

    1. I couldn’t agree more. Also stopped watching over 25 years ago. I do like series and movies though so Netflix and other services are great for this.
      And if there was something interesting on TV, you’ll see it the next day appear on YouTube. So if there was a really great amateur at Idols you can watch the 30 seconds of it on YT instead of wasting a whole hour on the complete show.

    2. >months without TV. You will never ever want to go back again.

      There it is! That year that the United States Government paid us all to continue watching TV, I bought my converter box, and found myself watching only the additional channel for the local public television station (documentaries and bonus runs of the better shows, at a more reasonable time) the third channel of another station (all ancient tv shows, all the time) and occasional dips into the 24 hour weather channel). Then I got married, and never bothered even transferring the box to the new location. Internet and each other’s company–I can’t even get interested in major sports, politics, or official news coverage version of what happens in the world. –And I grew up glued to the television, got a mass comm degree, and work for a media content provider (I can “eat our own dogfood” streaming via the web anytime I feel the urge).

    3. Seriously! we finally plugged in an antenna so my wife could watch the olympics and i couldn’t stand it! I’ll watch netflix, and amazon prime and that’s it! I will never pay for commercials! i may tolerate them, muted, when the programming is free. (free being a loose term, since i’m already paying by consenting to assault by advertisers)

      1. Same same – I had to go buy an HDTV dongle and setup a standalone machine to record the Olympics since I don’t have a TV. The end result is that you can watch the content in VLC, which has those lovely skip-ahead buttons.

  3. Another idea is to collect repetitive content and automatically suppress it.
    Let’s say the ad is:
    – Repetitive.
    – Longer than 1 Minute
    – Shorter than 7 Minutes
    All 3 matches – Trigger.

  4. Blocking ads via ntsc used to be easy – look for a ‘true black’ frame, which was used as the trigger for local tv stations to insert their ads next. Unfortunately, later on, they got wise to this and started doing things differently.

    1. A single frame, value 0? I recall reading a quote from Joss Whedon about how to insert a few seconds of black frames + silence for effect (Firefly series, I think). The networks didn’t like pure black frames (i.e. luminance zero), and they didn’t like pure white frames either (luminance 255), so his editor made them very-very-dark grey. That fits in with some documentation from Premiere Pro, which says to not use pure black or pure white – extreme values of luminance, as it could damage network transmission equipment, so you set luminance min and max parameters of 16 and 235. I guess a single frame wouldn’t do any harm.

      1. It’s coming back – they couldn’t use black frames for artistic/dramatic effect because it would trigger a fault condition (or maybe trigger “it’s time for ads now”) in the transmission equipment – so they found out how low they could go in luminance without triggering that condition.

    2. That’s also back when analog was King, and the downstream switcher (GVG) was used to insert a tape a/o local feed from the in-house studio. Now that digital is the norm, (I switched the station where I worked from A to D over 10 years ago…) there is no time delay and feeds are switched “hot”. Commercials are run from local hard drives, ready in microseconds, and requiring no “windup” like tapes. There might be a signal present (either audio or other wave) that could be used to “trip” the override to RasPi an audio stream or pics or a combo of the two…

      1. StepCorn Grumbleteats – Supposedly with network TV broadcasts including cable, there is a single video frame right before commercial break that goes black or near black for a few milliseconds. A human can’t see it but some sort of detector could. Then as it returns to content it does it again. ComSkip (not ComKill as I said before) uses this detection scheme as well as screen scraping the video screen for the presence or lack of of network logo. ComSkip also looks for overall video/audio changes too. It’s software based and is free. I assume a digitizer (ADC) is needed for your PC to capture A/V for analysis. The link is in this thread somewhere.

    1. That’s what I would do… but not every station in every country uses a “watermark logo”. Trying to detect the bumpers or the ads themselves is a dead-end street. Commercials are replaced, updated or just dropped each and every day.

  5. I think you can build database of advertisement start jingles that would be detected to start blocking. After the break there is often also a jingle or a moment of silence. Detecting this should be simpler and more reliable than analysing picture.

  6. In the mean time, I use the “Mute” Button of the remote. It is not a big deal, but it sure cut the crap out of comercials. You can even play with your family with changing the dialogs of the ads.

  7. If I remember correctly, if you have the original data accessible (rather than the HDMI output of some set-top box), the V-chip signaling can tell you if it’s a commercial or not in some cases.

  8. But you’re texting all through the show anyway, so an ad just gives you a few minutes to catch up. No need to do any complicated blocking just to “spite” the advertiser.

  9. Maybe a learning system. When a commercial comes on you slap the big blue button and when it’s over you slap the big green button. The machine does some sort of lossy compression and stores the patterns. During viewing the machine compresses the audio stream and compares it to the stored patterns, blanking the volume during detected ones. Commercials are so repetitive now it would provide significant benefit.

  10. Since this is a stream-based solution, I would think routing all of the traffic through a local proxy, altering the low-level network driver, or even a custom browser could achieve the desired results. The ads are typically served from a different server than the program content. This can be detected and either re-routed, or the content could be intercepted and just “blanked.” It could possibly be as simple as a DNS lookup trigger.

    I’m sure I’m oversimplifying the solution, but it seems to me that detecting the stream’s source is the easiest approach.

    1. True enough if it’s a general purpose or open device that you can do that with. This appears to be platform independent though. Cable co gives you a black box for their streaming service, should still work.

  11. When commercials starts, the audio level is higher than the normal show. This could trigger the switch, but should be connected with other factors, or you’ll have a movie switched off when shooting and explosions starts.

  12. I pitched this as an assignment for an advertising class in the 1970s, ostensibly based on data lines in the NTSC vertical blanking interval coding (which I had no idea about actually doing and likely would have never worked).

    Imagine the response from a bunch of advertising sorts for a product that weeds out advertisements….kind of like pitching cigarettes to respiratory therapists.

  13. The thing that annoys me the most is the pop-up ads that appear on the bottom left of your TV after a normal commercial break. As I understand it it comes in on the left vertical hold signal.

    I assume there must be some kind of flag that turns the ad on and off. If the hacker community can find the keys. The signal containing the ad can be sent to the “back” of the screen. It will look as if the ad didn’t exist.

      1. Usually they will advertise an upcoming program. I don’t like them because they cover up the bottom portion on the TV. When there are subtitles in the show.you can’t read them because the pop-up add is in they way.

  14. I used to have a DVR called ReplayTV that had an automatic ad-skipping feature (obviously on recorded shows). Unfortunately, they went out of business due to corporate lawsuits. I suppose the advertising companies didn’t appreciate a user-friendly ad-skippping box. I wonder if the mechanism that this box used to detect ads could be reverse-engineered.

  15. My low tech solution is to turn the set off, and guess when to it turn back on. The quietness gives me time to hear myself think. On average there’s 20 minutes of ads per hour, so I get to do a lot of thinking

      1. You might be right there buddy, all the razzle-dazzle our local TV station does on the news drives me nuts, just talking heads, and if your lucky, a minute of video per event. Just for sh*! and giggles, I’ll do a stopwatch on them

        1. BTDT! The worst is the Sy-Fi network. Tey will break for 5+ minutes before returning. That’s a fricking long time when you’re watching a good sci fi flick. If I have to watch that stupid Burger King advert one more time about “… somebody’s gonna’ get fired…” I’m going to scream! The BK crown wearing idiot reminds me of that arrogant pseudo-intellectual coke-head Robert Downey Jr.

      1. Most all news broadcaster use a tactic called “teasers”. Just before the commercial, they report some important news to be shown after the ad.
        I can’t decide which one was lower:
        1- 2 inmates have escaped from the county prison, we’ll tell you which way they were seen running after the break
        2- There has been found a malfunction in a “xxx” brand baby crib that could cause choking, we’ll tell you after the break !!
        I do the same thing, turn the boob tube off, forgetaboutit !

  16. I have to disagree with you in a detail about the book vs. movie part: in my opinion, the fact that demonstrates that Arroway was right is better solved in the movie:

    (SPOILERS FOR THE BOOK)

    In the PI number, sooner or later you will be able to find ANY sequence, so what Sagan says in the book proves nothing. In fact, I was very disappointed when I read the book.

  17. I have a VCR from 2000 that detected ads — in fact I think I still have it somewhere in the garage. I think it was a Panasonic. The way it worked was sort of a secret because they didn’t want to break it by telling everyone how it worked, but from the way that it sometimes didn’t work on certain channels, I suspect that it detected the station bug in the corner of the screen.

    Some stations (particularly CBS) have an annoying habit of showing the rating (e.g. “TV-14”) as the usual logo in the corner when they show a trailer for another show in a commercial block. I think that triggered the commercial detection to stop fast-forwarding and go back to regular playback mode. Other than that, it worked surprisingly well most of the time.

    Nowadays I watch almost no TV at all because of the never-ending repetitive commercials. The few shows I do watch, I watch on a DVR so I can fast-forward through the commercials. I don’t watch streamed shows because they usually don’t work if you have an ad blocker on your browser (and I’ll be damned if I turn that off), or they just won’t let you fast-forward through the commercials. I don’t understand why people will pay for services like Hulu that make you pay to watch shows with unskippable commercials.

    ===Jac

  18. In France and USA the sound-level detection for ad-blocking would not work now. They both passed legislation to eliminate loud adverts (aka TV commercials). The adblock of the olden days was a secret pattern in the raster signal. That has since been eliminated. Today there is a paid service database of advert timings by network. This very detailed database and the the old raster signal were not meant for TV consumers. It was made for local affiliates to know when network adverts were going o be broadcast so they could put in their own local advertisement. A while back I checked out the prices for the database subscriptions here in USA and they are prohibitively high to keep us consumers away from it. Maybe some blackhats could publish the timings for free? You have to Google it as I forget where they are now.

    Some plausible workarounds could be a crowd-sourced advert blog of sorts. The blog would be manned by volunteer button pushers that click the mouse button when a advert starts and stops allowing you to build a blog detection routine to trigger your mute button on your remote. However, the blog would need to be broken down by geography, network, time zone, etc. as here in USA we have many networks and time zones unlike British TV. Everybody is not watching the same thing at the same time.

    Another trick is Closed Captioning. There is an old device that listens for swear words in CC text and mutes the TV. Somehow that could be worked into capturing universal advert buzz words (or not)? Using the same CC model, a hacker could funnel the CC signal through his PC allowing the “case” to be detected. It appears that MOST networks (not all), use all UPPERCASE for normal programming then Mixed Case for adverts. This does not always work as the CC people seem to refuse to keep UPPERCASE as the universal CC model. They tend to type in Mixed Case during some modern movies. So nothing is foolproof.

    Listening for repetitive adverts in a local audio database (of 1st 5-seconds only) may work but it has to “learn” for a good while to be effective. Turning TV off completely works for single bachelors with no families, and just depend on Internet content. Watching the NEWS today is a prerequisite as the crazy weather and crazy world politics must be watched so you can stay informed of world events for your own personal safety. However, try and get your Luddite wife to stop watching HSN, QVC, etc, and her favorite soaps and reality TV shows on the big family TV in the kitchen, bedroom, den, and living room. Try telling her she’ll have to log into your PC or MAC to watch it online. Try telling your lazy kids they can’t watch cartoons and other kids programming on the old family large screen TV any more. It’s not that simple! You will become like a bachelor for real! :-)

    1. Oh and here in USA our FCC eliminated analog TV. It’s all digital here. And our cable companies have followed suit. Now we have fully-addressable digital cable boxes complete with built-in spy apps to eliminate Nielsen Ratings. Yes they KNOW what you are watching and when. They know when you turn it off too. The scary part is that there are rumors that there is also audio and camera intercept on the boxes too. This is said to help tailor targeted adverts to certain communities. It is said it is all captured anonymously. Some how I find that hard to believe.

      A cable company in Chicago Illinois (USA) fully admitted they were doing that back in the early days of addressable digital cable boxes to allow for customers to have 1-on-1 conversations with customer service. Then there was no more talk of it when it rolled out to rest of USA. And they charge ridiculous cable rates and feed you TV adverts for up to 5 minutes a commercial break! You could be listening to a heartbreaking and shocking story about something topical and then you get an earful of an inane advert for something I would never buy right in the middle of the show. Then the damn thing takes forever to return to the show. I usually just turn it off and walk away loosing interest in what I was watching.

      And this new $20/month streaming service with scary looking Danny “Machete” Trejo called SLING TV? Now that is just stupid! Why pay for something I can get from NETFLIX for $9/month or from Amazon Firestick? Or totally free FULL TV/movies at Project Free TV (run it NoScript enabled though). But Danny is right about paying US cable companies over $100/ month for TV complete with stupid and long TV adverts!!! Are US cable companies double-dipping?

      1. Oh and another thing, our federal government can break into the addressable boxes to break into what were watching on ALL channels to give us Emergency Broadcasting Network stuff. They do it during the graveyard shift (at night) to test it. And it takes over ALL controls too. I tried to defeat it and it just locked up the box until it was done. And they do it at the worst times in the middle of a good movie!!! Usually from the NWS (National Weather Service). But with the new PARALLEL CONSTRUCTION info-sharing among US federal agencies, I wonder when another N*** agency will be “addressing” the boxes too. They can and do do it with your laptop’s built-in camera and mic. Advertisers use it too.

        Need to put white noise generator and cardboard dodge in front of boxes maybe???

  19. So it’s called a bug, I didn’t know. Must Exterminate, Exterminate for total Dalek victory!
    The last greatest hope, Babylon 5 on late night local TV with only two brief bugs per hour show. Those were legit ID’s. That was before the turn of the century. Now we have a gaggle of holeywood whores posing in the corner of the screen, placement of adverts in programs will have no limit.
    Vladimir Zworykin had it right, in the 80’s he declared the power switch off mode to be his greatest invention.
    I listen to a lot of NPR and other independent public programing. I need an audio “ad-killer” for that woman that reads all of the NPR underwriters. One voice all the time! Some kind of formant profiling should work in real time, somebody up to it? She has the most smug over modulated kindergarten teacher delivery of anyone but our enthusiastic Purdue Kindergarten teacher-announcers.

    1. echodelta – All you need is to feed your audio through your sound card so you can use the HTML5 Audio tag to toggle the audio off and on. (Of course if your listening to NPR on said laptop no need to do that). Then when NPR starts up you know what they will say word for word at that annoying part. Just download a speaker independent STT (speech-to-text app) like Google Voice (?) or something cheaper. STT is free in Windows XP and higher (STT recognition is built in). Then when the trigger words are said it mutes your PC audio for let’s say 60-seconds.It could mute or play your favorite song (MPEG download).

  20. Thanks to [Quin] I think we may have nailed it. A field programmable image analysis web cam system that looks for changes in TV channel bug logos in corners of screen. They tend to be ubiquitous and static. TV shows like advertising who they are during your movie or TV show. However, they disappear for TV adverts – BINGO! GOTCHA! TV advertisers…

    Here’s a preliminary diagram. Maybe somebody could evolve this muse of an idea:

  21. I wonder why they not yet introduced some “feature” to lock your TV while advertising (no mute, no channel change, …) – or does this already exists? I almost never watch TV and if i do i record the program i want to watch so i can skip the adds quite easely. The only thing that makes me really angry is that the recordings on the HDD of my receiver (TV over the telephone line) are encrypted, no way to copy to PC. WTF??? The channels are free, not pay-TV.

    1. In USA that’s how the Emergency Broadcast Network message works on digital cable networks. It totally seizes your box on all channels to make sure you see the local or national emergency. Not sure about the volume but it would be really weird if they could turn on a previously powered off TV…

      1. Some HDMI TVs have that feature, usually intended to turn the TV to the appropriate input when you turn on your Blu-ray. I believe a similar feature exists in the UK with the older SCART, but don’t quote me on that.

        The feature is spotty at best as I can only get it to work between a Sony Blu-Ray and a Sharp AQUOS. My other players and TVs don’t behave this way even though they all have the same “feature”.

        I wouldn’t worry about it though. The Chinese are very considerate of us Americans and happily supply the market with HDMI adapters that strip all sorts of junk in the signal out. I have little doubt tue Chinese will supply the world with an HDMI middle-man that explicitly blocks the power-on signal if they haven’t done so already.

  22. In the days of analogue, MTV Europe had an experimental system for inserting local ads at the downlink or head-end. The downlink had a video server and a switch. The Europe wide broadcast from London had a code inserted into one of the blanked lines at the top of the picture. I cant remember which line but it was the one above the Teletext data. The remote server would detect when the signal changed, and switch from the satellite to the local server.

    I wonder weather this sort of thing is still used? I know that some of the DTV channels here in the UK which are not HD have problems with aspect ration converters being switched in and out when the show is 4:3 and the ads are 16:9 anamorphic. My TV has auto switching and it can be very strange when the ARC switch defeats it.

    Digital TV transmission streams have all sorts of additional data embedded. Would there be idents from the original content?

    I’m a retired editor so I haven’t looked at any of this stuff for a while, but I have a friend who works at the main BT TV switching centre in London. I am going to ask him tomorrow and if he has anything interesting to say I will report back. This post has triggered my curiosity!

    1. chandwer – Well jschwalbe’s COMSKIP kinda’ sorta’ does that. It not only scans the video image for network logos presence or lack of logo, it also analyzes the video waveform signal and audio signal to detect a baseline of your desired TV show/movie content. It then kinda’ sorta’ acts like a A.I. program (or neural network) to analyze and sense or detect (aka learn) a TV commercial break and then when the desired content returns. It is somewhat buggy (i.e. falsing) but from what I read at the website it works quite well, and it’s FREE!

      But none of this stuff is Criticalality-One. It’s not critical that it work 100% of the time. Just as long as it tries to kill most of the adverts is good enough. Who cares if you have to watch one advert or miss some of your content for a few seconds or you have to manually intervene?

  23. adblock & zero interstial ads: usenet

    To avoid morally problematic piracy I pay the local ISP for a tv plan that I don’t hook up to hardware that I don’t rent. TV episodes are stored ZFS style. Xmpp Texting motification of new episodes.

    If you only watch air channels there is no piracy.

  24. Look up in the vertical interval. Often a loss of the Close Captioning carrier is a hint that the program has transitioned to commercial or back. Better yet, often the VITC (Vertical Interval Time Code) will have a sudden discontinuity when the VITC for the program changes to the VITC for the commercial.

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