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  1. Member brassplyer's Avatar
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    I was watching yet another YouTube video with combing lines and wondering why isn't all modern video shot progressive? Is it correct that the native functionality for all HDTV's is progressive and all computers play progressive video? Why is interlaced even still a thing?
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  2. Even if it's not shot interlaced it's often broadcast as interlaced. The two main formats in the USA are still 720p60 and 1080i30.
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  3. Member brassplyer's Avatar
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    Originally Posted by jagabo View Post
    Even if it's not shot interlaced it's often broadcast as interlaced. The two main formats in the USA are still 720p60 and 1080i30.
    Why so?
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  4. Because broadcast standards evolve very slowly. So you don't have to buy a new TV every few years.
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  5. Originally Posted by jagabo View Post
    Even if it's not shot interlaced it's often broadcast as interlaced. The two main formats in the USA are still 720p60 and 1080i30.
    Same in PAL countries: 720p50 or 1080i25.
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  6. Member brassplyer's Avatar
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    Originally Posted by jagabo View Post
    Because broadcast standards evolve very slowly. So you don't have to buy a new TV every few years.
    Maybe I have a misconception - you say it's "often" broadcast interlaced, which suggests it's not always. Don't all HDTVs accept a progressive signal? If so, why would anyone continue to broadcast an interlaced signal - my understanding is this is a technology utilized by CRT tvs and no longer needed by HDTVs? If everyone broadcast progressive in the same way that progressive is broadcast now why would that necessitate a new tv? The typical relatively short lifespan of HDTVs notwithstanding.
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  7. As always there is trade of between for example bandwidth and costs - interlace allow to deliver smoother motion at a cost of the vertical resolution - interlace video may pretend to be almost as good as progressive video but it doesn't require so high bitrate as same resolution video but progressive.
    It is quite important to remember that MPEG-2 was designed in times where typical decoder was equipped with 1..4MB of RAM (shared between frame buffer, application, OS and GUI), also computational complexity was rather high when compared to available CPU power those times (CPU closer to 486@80MHz, perhaps somewhere first Pentium@60MHz). Next decoders iteration need to share some infrastructure (so called legacy) so still no place for purely progressive content, luckily H.265 is designed as progressive codec (RAM, CPU's are more powerful).
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  8. Originally Posted by brassplyer View Post
    Don't all HDTVs accept a progressive signal?
    The question is at what temporal and spatial resolution. It's not so long ago that HDTV's did not yet support 50 or 60 fps at "full" HD resolution of 1920x1080. The limitation was at 1280x720p and 1920x1080i.
    (Even today with 4k one could double the temporal resolution with interlacing technology btw.)
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  9. Originally Posted by pandy View Post
    Next decoders iteration need to share some infrastructure (so called legacy) so still no place for purely progressive content, luckily H.265 is designed as progressive codec (RAM, CPU's are more powerful).
    As far as I know both the standard H.265 and the encoder x265 still do support the interlaced format. Maybe it's hardly used anywhere, I don't know.
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  10. Member Cornucopia's Avatar
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    @brassplyer, ATSC (the digital successor to NTSC) version 1.0 (the one that has been fully in place officially since 2009 but actually longer) allows for 720p60 and 1080i30 (and a few other variations), but notice those are both roughly equivalent in terms of bitrate/bandwidth requirements. Some broadcasters opted for primarily 1080i30 for better resolution, others opted for primarily 720p60 for better motion (sports!), others opted for an even split of both.
    ATSC 2.0 was folded into ATSC 3.0, which 3.0 is only now being rolled out by broadcasters (~25% in place currently). This will allow for newer codecs than MPEG2, higher rez, and more primarily progressive material. But that also requires the users TVs or receiver/tuners support ATSC 3.0. Even with brand new TVs not many of them do.

    So, considering the slowness up uptake, and the continuing of legacy methods which include interlace, and the trove of legacy interlaced material, it is no surprise at all that we would still see interlace in use.

    Yes, for a consumer who is shooting new material, with (hopefully) more modern cameras, I also would recommend they use the 1080p60 or better options.

    And in 5 or maybe even 10 more years, we should see a noticeable decline in the amount of interlaced stuff. But it probably won't fully go away until there is some tech cutoff which mandates discontinuing SD or interlacing. And we've seen how some of the public react to mandates.


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    Originally Posted by brassplyer View Post
    Originally Posted by jagabo View Post
    Because broadcast standards evolve very slowly. So you don't have to buy a new TV every few years.
    Maybe I have a misconception - you say it's "often" broadcast interlaced, which suggests it's not always. Don't all HDTVs accept a progressive signal? If so, why would anyone continue to broadcast an interlaced signal - my understanding is this is a technology utilized by CRT tvs and no longer needed by HDTVs? If everyone broadcast progressive in the same way that progressive is broadcast now why would that necessitate a new tv? The typical relatively short lifespan of HDTVs notwithstanding.
    There are still plenty of people with an old HDTV somewhere in the house that they still use. The oldest working HDTV in my family (my mother's 720p bedroom TV) was purchased in 2008. I checked the manual and it doesn't support 1080p video input from any connection.
    Ignore list: hello_hello, tried, TechLord, Snoopy329
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  12. Member Cornucopia's Avatar
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    It is conceivable that there are still folks out there using a CRT with one of those outboard "transition" ATSC DTV tuner boxes. Esp. since those older CRTs were built much more sturdily.

    Scott
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  13. Originally Posted by Sharc View Post
    Originally Posted by pandy View Post
    Next decoders iteration need to share some infrastructure (so called legacy) so still no place for purely progressive content, luckily H.265 is designed as progressive codec (RAM, CPU's are more powerful).
    As far as I know both the standard H.265 and the encoder x265 still do support the interlaced format. Maybe it's hardly used anywhere, I don't know.
    Of course you can split interlace frame on two fields - something like PAFF for H.264 but AFAIK there is no MBAFF so interlace may be considered as not a feature but rather hack or kludge for H.265 - also H.265 was designed with UHD resolution on mind (H.265 is less efficient for less than UHD resolutions and all UHD sources are progressive AFAIK).
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  14. Originally Posted by usually_quiet View Post
    There are still plenty of people with an old HDTV somewhere in the house that they still use. The oldest working HDTV in my family (my mother's 720p bedroom TV) was purchased in 2008. I checked the manual and it doesn't support 1080p video input from any connection.
    I have LCD TV from 2006 - still working fine and it also officially not support 1080p yet strangely it is capable to display 1080p (currently i have such configuration not by choice but simple IPTV decoder do not allow to select video mode manually - it is so smart and clever that he don't need customer at all).
    Negative side of such 1080p mode is lack of possibility to adjust video settings - only contrast and brightness works also colors looks like slightly "undersaturated".
    So manual may be not entirely in line with TV capabilities.
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    I don’t shoot much video anymore but I have 3 Canons that shoot 60i and 30P, and I
    just don’t have the cabbage to go 60P. 4K is out of the question, especially if I need at least 2 cameras.
    Maybe economics plays a part in why interlaced is still viable.
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  16. Member brassplyer's Avatar
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    Originally Posted by Sharc View Post
    Originally Posted by brassplyer View Post
    Don't all HDTVs accept a progressive signal?
    The question is at what temporal and spatial resolution. It's not so long ago that HDTV's did not yet support 50 or 60 fps at "full" HD resolution of 1920x1080. The limitation was at 1280x720p and 1920x1080i.
    (Even today with 4k one could double the temporal resolution with interlacing technology btw.)
    I wasn't an early HDTV owner - so early HDTVs didn't roll out with the same specs as later pre-4k models.

    The answer to my question ultimately is that there's a lot more to it than I was aware of.
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    Originally Posted by Cornucopia View Post
    And we've seen how some of the public react to mandates.
    Scott
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    "FREEZE PEACH, FREEZE PEACH!!!!!"

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    Dear participants!

    You are ALL Wrong.

    Most TV channels use neither interlaced nor progressive video.

    They broadcast most of their content in progressive segmented Frames.

    https://en.wikipedia.org/wiki/Progressive_segmented_frame

    Only the Sport events and activity shows are broadcasted in true interlaced way.
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  19. Originally Posted by Truthler View Post
    Dear participants!

    You are ALL Wrong.

    Most TV channels use neither interlaced nor progressive video.

    They broadcast most of their content in progressive segmented Frames.

    https://en.wikipedia.org/wiki/Progressive_segmented_frame

    Only the Sport events and activity shows are broadcasted in true interlaced way.
    No, YOU are wrong. While media they play might have the same framerate (half of the field rate), it is still converted to interlaced video. Studio cameras still shoot in 50i

    Only the Sport events
    Actually, most sports broadcasts are 720p50

    Lastly, here's a screenshot of an analogue tv capture i did back in the september. While it may not prove that the image sent is progressive, it clearly shows that the signals field rate is 50 and not 25 (further proving that television doesn't use interlaced video

    Image
    [Attachment 63456 - Click to enlarge]
    Last edited by rrats; 19th Feb 2022 at 10:00.
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    Originally Posted by s-mp View Post
    Originally Posted by Truthler View Post
    Dear participants!

    You are ALL Wrong.

    Most TV channels use neither interlaced nor progressive video.

    They broadcast most of their content in progressive segmented Frames.

    https://en.wikipedia.org/wiki/Progressive_segmented_frame

    Only the Sport events and activity shows are broadcasted in true interlaced way.
    No, YOU are wrong. While media they play might have the same framerate (half of the field rate), it is still converted to interlaced video. Studio cameras still shoot in 50i

    Only the Sport events
    Actually, most sports broadcasts are 720p50

    Lastly, here's a screenshot of an analogue tv capture i did back in the september. While it may not prove that the image sent is progressive, it clearly shows that the signals field rate is 50 and not 25 (further proving that television doesn't use interlaced video

    Image
    [Attachment 63456 - Click to enlarge]
    No, Intelaced = 60 or 50 motion fields. If you progressively scan 30 or 25 frames and you put it into 60 or 50 half pictures (fields) it not interlaced anymore.

    TV channels use a so-called MPEG DASH systerms, which can contain a signal which decides whether the content is progressive segmented material or true interlaced.

    Older and cheaper TV sets de-interlaced practically everything, they could not understand that signals. Modern HD TVs if they got a signal for interlaced, they will deinterlace it, if they got a signal for Progressive Segmented Frames, they will simply put together the fields into full progressive frames, and simply prompt them 2 times on the screen. With this PSF methode, they won't lose quality with so-called deinterlacing methodes.
    Last edited by Truthler; 19th Feb 2022 at 10:26.
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  21. Capturing Memories dellsam34's Avatar
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    Originally Posted by Truthler View Post
    Dear participants!

    You are ALL Wrong.
    Oh boy, He is off the hibernation season.
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  22. NBC and CBS standardized on 1080i. ABC and Fox standardized on 720p. All O&O stations conform to the network's standard as do most network affiliates. If you're going to deliver to a network or station you'll need to conform to their standard.

    IMO it should all be 720p but they didn't ask me.
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  23. Member Cornucopia's Avatar
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    So-called, huh?
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  24. Originally Posted by brassplyer View Post
    Why is interlaced even still a thing?
    Because of legacy. Analog TV was interlaced. Japanese HDTV was interlaced. When digital TV was considered, 1080i format was pushed by Japanese companies because they already had necessary studio equipment. Check out this article for a start: The History and Politics of DTV. If you have time, this is a great source of historical documents: Tech-Notes.TV.
    Originally Posted by Sharc View Post
    Originally Posted by jagabo View Post
    Even if it's not shot interlaced it's often broadcast as interlaced. The two main formats in the USA are still 720p60 and 1080i30.
    Same in PAL countries: 720p50 or 1080i25.
    Some 50Hz countries broadcast in 1080p50 since, I believe, 2016.
    Originally Posted by Cornucopia View Post
    Some broadcasters opted for primarily 1080i30 for better resolution, others opted for primarily 720p60 for better motion (sports!), others opted for an even split of both.
    Motion is the same for both - 60 images per second. I am surprised you make this distinction. Vertical resolution for 1080i depends on content and on deinterlacer, and can roughly range from as low as 540 lines @ 60 images per second with a simple bob deinterlacer to full 1080 lines if the actual content is shot at 30 fps or less. My TV set does not have a great deinterlacer, I see horrible artefacts when watching 480i broadcasts.
    Originally Posted by Truthler View Post
    They broadcast most of their content in progressive segmented Frames. https://en.wikipedia.org/wiki/Progressive_segmented_frame Only the Sport events and activity shows are broadcasted in true interlaced way.
    Traditionally, in the U.S. scripted dramas are shot at 24p, hence 2:3 pulldown, not PsF. Any decent TV is capable of IVTC-ing 2:3 pulldown to 1080p24, although you still get judder if you panel is native 60 Hz. In Europe they have been using 2:2 pulldown forever, speeding up movies to 25 fps. Without low pass filtering 2:2 pulldown is equivalent to PsF.
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  25. Member Cornucopia's Avatar
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    Motion is NOT the same, as there is discontinuity when not going between lines (with 1080i).


    Scott
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  26. Originally Posted by Cornucopia View Post
    Motion is NOT the same, as there is discontinuity when not going between lines (with 1080i).
    Um, I did not get this. Can you elaborate? A link will suffice. Thank you!
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  27. Regarding usage of PsF on American TV - it seems they use it more often indeed for reality shows, carefully controlling for the motion. I am skipping some test footage I recorded off air frame by frame, and Open House is sent as PsF by a local NBC affiliate.

    Same thing with beIn Sports Extra. Well, not exactly. It seems they have deinterlaced fast-motion video into 30p first, I see ghosting. After all, who in the right mind would shoot sports at 30p?

    These greedy bastards try to make the recent dramatic drop in bitrate caused by the spectrum repack and the rise of diginets less noticeable.
    Last edited by ConsumerDV; 3rd Apr 2022 at 16:25.
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  28. Member Cornucopia's Avatar
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    No link. Let me describe it for you.

    Picture a red dot on centered a solid field of white, or better yet say white on black (color is further affected here due to subsampling).
    Let's say the dot is 1 pixel high and wide, and moves at the pace of one pixel per field/frame (whatever the next motion increment).
    If moving vertically, both field-based (1080i30) and frame-based (720p60) are identical (though the resolution is different obviously), and you will see that pixel move through on every line in either format.
    If the pixel is moving horizontally, however, the next motion incremental on the SAME line in 720p is like the vertical, but there is no pixel on the same line in the next motion incremental for 1080i, for the simple reason that that line doesn't exist in that time increment. Only the lines above & below (which a 1 pixel size would not show up on). Then it next pops back in again (but moved further), then out, then in, etc.
    Diagonally, it is a mix of both effects.
    This is somewhat mitigated by the higher resolution overall in 1080, but not completely, and the interlace flicker and perception of darker values (due to PWM effects) is still there, in the interlaced version. Another mitigating factor is the fact that most reallife objects span multiple pixels, and don't have abrupt edges when recorded on the sensor. But the difference is still there and still noticeable for anyone trained to see it.


    Scott
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  29. Member Skiller's Avatar
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    Cornucopia is right.
    His example also nicely demonstrates why interlaced video needs to be low-passed on the vertical axis. You do not want a detail to be present in one field but completely missing in the other. In cameras this happens as early as at sensor level.

    If you were to shoot a static scene on a tripod with the same camera two times, once with the camera in interlaced mode, once with the camera in progressive scan (same resolution of course). You will find that the progressive scan shot has more vertical detail and that is purely due to the ommitted low-pass required for interlaced video.
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  30. Ah, this is just an edge case that does not change the motion characteristics overall. If this were a ball, not a single pixel, it would move with every field. Sure, it won't look as well defined as with progressive scan, but at least there is "live" motion of 60 images per second, not 30. Usually TV pros try to avoid fine details like fine mesh on a shirt, etc, to avoid moire, line twitter, and the effect you described, or run the video through low pass filter. As you said, this effect is greatly reduced in HD, as there are hardly ever objects that are one line high. Even the dumb bob deinterlacer produces decent result most of the time. On 480i these issues are more pronounced. A 24-hour cartoon subchannel on local PBS affiliate is in 480i, and sharply defined lines at small angle to the horizontal look horrible on my TV, which is not very smart. I wonder why would not they deinterlace in the studio and use 480p60, this format is included in ATSC 1.0.
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