Why you should choose H-SBS over H-OU

Introduction:
You can either skip to the bottom of the article if you want to see the screenshot comparisons, or read through this to get the details behind the reasoning and testing methodology.

It’s common for 3D videos to be encoded in one of two formats: H-OU or H-SBS. These stand for Half Over-Under and Half Side-By-Side. In the former, the video for the left eye is stored above the video for the right eye, while in the latter the video for the left eye is stored to the left of the video for the right eye.

Getting H-SBS or H-OU instead of SBS or OU is the best option if you are going to watch the video over a network using DLNA, which is how most media servers work, since the full resolution won’t be used for full SBS or OU anyway. It will only display half of the pixels.

Additionally, a good encoder will have used a high quality resizer to halve the resolution in a H-OU or H-SBS file, meaning that the H-SBS/H-OU file will actually look higher quality when streamed over your network than a SBS/OU file – it’s unlikely that the media server and other hardware will use a slow, high-quality resizer while you play it, it will most likely use a quick, low quality one.

Why you should choose H-SBS over H-OU:
When you increase the resolution of an image – which is what software on your playback equipment (TV, monitor, etc.) needs to do to a H-SBS/H-OU video in order to stretch it back to its original size – the higher the starting resolution is, the better your resulting image will look. If you try to double the resolution of a 50×50 image to 100×100, the results will be inferior to doubling the same image from 1000×1000 to 2000×2000.
This may seem obvious. Of course a resizer will be able to be more accurate when it has more details to start with. Even though you are doubling the image in both situations, the situation that starts with the most details will result in the highest accuracy.

With H-OU, each eye sees a maximum resolution of 1920×540. This usually ends up being more like 1920×400, with the other 140 vertical pixels being the black bars at the top and bottom of the video frame. This gives us a great, full horizontal resolution, but a very small vertical resolution. In fact, this vertical resolution is even lower than DVDs, which can use up to 576 vertical pixels (typically between 404-484 for a cinematic movie).

By contrast, with H-SBS, each eye sees a maximum resolution of 960×1080, which usually ends up being more like 960×800 after the black bars are taken into account. This gives us a much more even selection of detail.

Both methods give us the same amount of pixels in total – 1036800 pixels per frame – but H-OU makes it harder for a resizer to enlarge the image as accurately, since it’s making the height so tiny. H-SBS halves the bigger number, resulting in two decent sets of rows and columns (960 and 800) instead of one large set of columns (1920) but one tiny set of rows (400).

Image examples:
It’s all well and good to talk about it, but seeing is more powerful.
For the following images, I’ve taken the original image (1920×800) and halved it using a bicubic (neutral) filter – the best choice for an image that will be enlarged later – then restored the original resolution using one of two resizing filters. One is Nearest Neighbor, which is a low quality filter, and the other is Bicubic Smooth, which is a high quality filter. Most TVs will have quality somewhere in between the two. My Panasonic VT60 seems to use something similar to Nearest Neighbor, which results in some very low quality moments with a H-OU source.

I’m using a website called Screenshot Comparison, which allows you to compare images by holding the mouse cursor over them, it’s a very convenient method.
For these comparisons, the H-OU image is visible when the cursor is not over the image, and the H-SBS image is visible when the cursor is over the image.

Image 1 using Nearest Neighbor
Image 1 using Bicubic Smooth
Image 2 using Nearest Neighbor
Image 2 using Bicubic Smooth

The most obvious parts to look at are the grills near the top of Image 1, the table near the bottom right of Image 1, and the details (lights, lines) on the ship in Image 2.

Important note: This article applies to monitors and TVs that use active 3D, not passive 3D. If your 3D glasses take batteries, plug in to recharge or have a button on them, then you use active 3D. Passive 3D TVs (like newer LG and Vizio TVs) should use H-OU, as widezu69 mentioned in the comments section below.

23 Comments

  1. Hey Klaus,

    This is a good post, although I have to add a point here. While in most cases, perfectly demonstrated by your images, H-SBS is the preferred option, however, there is a place for H-OU and that is with passive 3D televisions.

    TV’s which do passive 3D rely on H-OU because that is the 3D configuration of the screen where left eye sees line 1, right line 2, left line 3 etc up to line 1080. If you feed it a H-OU image, the display will choose the top half of the frame and alternate it with the bottom half. Because each line is mapped perfectly in a alternating 540p arrangement, there is no scaling of any kind making it perfectly matched. All the information in a 2x 1920×540 H-OU is fully resolved into a 3D frame with a native that is as sharp as the source material intends. this method ensures that the TV shows every pixel in the frame.

    However, if you feed a H-SBS image to the display, because of the way the screen is polarized for the glasses, when the TV puts the image up, it will have to stretch the horizontal resolution and reduce the vertical to half anyway. Therefore, a 2x 960x1080p 3D frame is stretched horizontally first, introducing interpolation, then the vertical resolution halved and then split alternating lines for the two eyes on the display. The final 3D image actually only resolves a 960×540 resolution. All the 960px horizontal resolution is displayed albeit stretched and and interpolated but the vertical 1080px is reduced to half for the 3D arrangement.

    As I said before, this only applies to passive 3D TVs that show alternating lines for 3D. This would not be an issue if the TV was polarized to display 3D images in alternating vertical lines but as it stands, horizontal lines is where we are at so H-OU has to stay.

    Also this doesn’t matter for Shutter style 3D tv’s, nvidia 3D vision and 4k 3D tv’s because they all resolve the full 1080p regardless of 3D frame arrangement.

  2. SubJunk

    June 16, 2014 at 10:52 am

    Hey mate, good to hear from you 🙂 You’re right about passive 3D, I have added a note about it to the bottom of the post 🙂

  3. Thanks Sub! Yeah I’m still on the video scene, constantly following your blog regarding updates to scripts, modifying for myself for realtime playback.

    This is a really interesting post, I never though the difference between HSBS and HOU was that much and demonstrable. I still have a passive 3D TV so I’m sticking to HOU but once I get a 4k 3D TV (simply because they resolve 1080p per eye, but still passive without flicker) like one of the new Sony ones I’ll be moving to HSBS and keeping my HOU collection because it won’t matter any more.

    I also find that 60fps conversion on 3D films works well, eliminates head-aches and also because each eye frame is different, therefore the interpolation is slightly different, any artefacts in 3D are different per eye and the brain just chooses to ignore them. I have watched a film with my GF and I can spot artefacts because I was looking for them but she didn’t whereas she can spot artefacts in a 2D video. It’s weird but also really good.

  4. Hi,

    I’m getting this LG TV, 55UB850T http://www.lg.com/in/tvs/lg-55UB850T

    So I would assume its a Passive 3D TV, for example if I want to download a 3D movie and put it in my thumbdrive and watch. Which one of the below should I get?

    1). Hercules 2014 3D 1080p BluRay x264-NODLABS
    2). How to Train Your Dragon 2 2014 3D 1080p BluRay Half-SBS x264 DTS-HD MA.7.1-RBG
    3). Hercules 2014 3D 1080p BluRay Half-OU DTS-HD MA 7 1 x264-LEGi0N

    All are MKV’s ( I would assume the LG TV mentioned should work?) and file size above 4 GB which is the max a FAT32 file size limit is for a thumbdrive. So if I format it into NTFS, would I still be able to play the video in 3D?

    Thanks and cheers

  5. SubJunk

    November 6, 2014 at 10:18 am

    @jelloman I can’t endorse downloading copyrighted content, buying the Blu-ray is the best course of action. I’m not sure it’s possible to format most thumbdrives to NTFS. I develop a program http://www.universalmediaserver.com which should be able to stream 3D movies from your computer to your TV.
    That TV should be better with H-OU than H-SBS based on it being passive, but I’m not sure if it’s different with 4k.

  6. Hello,

    I just got a new LG 55LB650V with passive 3D.
    I downloaded a couple FullHD 3D examples from different sources to look at the image quality. I have SBS and OU examples. Sometime the TV automatically switches on the 3D sometime not. I have to set the mode manually.
    Because the LG 55LB650V can switch between SBS and OU, is there still a difference and should I prefer OU?

    Thanks

  7. SubJunk

    November 21, 2014 at 9:39 pm

    @Carsten I hope you enjoy your new TV! Yes OU should be the best choice for you

  8. Hello. Thanks for the explenation. But what about TV’s where I can choose the 3d mode? HOU or HSBS? Im talking about a new LG 3d tv with passive technique.

    regards

    alex

  9. edit: checked some videos on youtube. but i cannot see much difference?

  10. I understand your math with regards to having more pixels in SBS vs OU.

    But I would like to hear your thoughts about my reasoning of OU vs SBS.

    I feel in OU you are compressing more of the part of the movie that already has 17-18% of “nothing” (black bars)
    Secondly most panning in movies is horizontal,
    So if you play and switch between top & bottom, i feel you wouldn’t lose as much als when playing the same in SBS.

    As for sequential/ stacked or full 3D.
    If feel the same, you will indeed have full HD.
    But i think that when there are scenes with fast action, panning,
    you would experience more stutter since you you are looking at 12 FPS
    frame 1L+1R, 2L+2R, 3L+3R, 4L+4R, 5L+5R, etc. etc..

    while in both 3D half SBS & OU you are looking at 24 FPS
    frame 1merged, 2merged, 3merged, 4merged, 5merged, etc. etc..

    Again, i might be wrong, it’s just how i think about it & love to hear your opinion about it & maybe i’ll understand your reasoning of this.

  11. Hi guys, very interesting read!

    I’m wanting to play some 3D files (actually *will* try when I return from my trip and get home with the items..).

    I have a Playstation 3D monitor, and glasses (active type since they power, charge, etc), and as a source to feed it I can use a PC, a WD Live TV or a console (XB1/PS4).

    Reading this I should be getting some Half SBS files, but what options do I have hardware/software wise to get them to play in actual 3d..? (or rather what of my stuff will actyually play these properly)

    Thanks!!

  12. SubJunk

    December 29, 2014 at 8:05 pm

    @Walter I don’t have experience with Playstation 3D monitor but I’d guess that’s all you need – just play the 3D video and set the monitor to 3D mode, then switch on the glasses

  13. I did a similar comparison using photoshop to shrink and resize again a full hd photo (full hd photo whithout black bars). What is clear to me is that the OU result blurs horizontal lines and SBS blurs vertical lines. At the specific photo OU result looked better than SBS overall but i think that it has to do that there where more vertical lines on that photo. So I think that because of these cinematic black bars on the movies (up and down) maybe its better to choose SBS to loose less image information, but I believe that it has to do with the movie images too… So I don’t have a clear choice between OU and SBS 3D…

  14. P.S. Happy new year to all…!!!

  15. There is the image. Don’t know how to post a url, sory…

    http://screenshotcomparison.com/comparison/106910

  16. SubJunk

    February 16, 2015 at 11:03 am

    @George gr yes I think in some scenes OU can be better like you said, but I think on average SBS will be better. Happy new year 🙂

  17. Your reasoning is incorrect. Yes, it’s about resolution, but not about total number of pixels, but the pixel pitch (pixels per length unit). Half-SBS and half-OU have the same pixel pitch, just in different direction. So, as George g wrote, it will “blur” lines either horizontally or vertically, so if the image has more vertical detail (such as sharp horizontal lines) then half-SBS will produce better quality and if the image has more horizontal detail (such as sharp vertical lines) then half-OU will produce better quality.

    The black bars at the top and bottom also make no difference what so ever, because the resolution reduction will be the same in either case.

    And your 50×50->100×100 vs 1000×1000->2000×2000 analogy doesn’t work like you explain it. If those 50×50 pixels are representing the same image as the 1000×1000 then the latter has 20 time more pixels per length unit, so of course it’s better quality (but irrelevant to the case at hand, where the pixel pitch is the same). OTOH, if those 50×50 pixels is an exact copy of a 50×50 part of the 1000×1000 image then the result will be the same and the 100×100 will be exactly the same quality as the 2000×2000 (albeit just 1/400 of the complete image), because they have the same pixel pitch.

    Let’s assume there is, on average, the same amount of horizontal and vertical detail. (Maybe someone would like to research this?)

    Half-SBS and half-OU will produce exactly the same quality after the image is resized back to full-SBS or full-OU, which is the case for active 3D TVs, and also for passive 3D TVs that have 2 * 1920×1080 pixels. Passive 3D TVs which have only 1920×1080 pixels and horizontal polarized lines half-OU will be much better quality.

    Since half-OU is not worse than half-SBS, but in some cases considerably better, you should always use half-OU.

  18. Jakob Rosenberg

    June 28, 2015 at 6:44 am

    As MarcusS pointed out, your reasoning is flawed.

    Imagine a series of adjacent circles (ooooo…). Each circle’s height is 100% relative to the screen. On a 1:1 screen, you will see one circle. Regardless of which way you half the resolution, the quality of the circles remain the same respectively. It’s the same visual reduction whether it’s vertical or horizontal. A 2:1 or 3:1 etc monitor will be able to show more adjacent circles, but the loss will remain the same regardless of which whether the compression is done vertically or horizontally.

    Saying that screen aspect ratio is factor is like saying that circles will be less lossy if you stack them on top of each other rather than side by side. Fact is, the circles are equally lossy, regardless of which way you compress them and which way you stack them.

    What matters is which direction has the the highest detail / length ratio and also whether the human eye spots more details horizontally than vertically.

  19. For passive 1920×1080 displays it is clear: half-OU is the ONLY choice to make (see widezu69’s explanation).
    And in general I have to agree with MarcusS that half-OU is ALWAYS better and I think even for a reason more.
    Our eyes are arranged horizontally and stereoscopic depth is perceived in the horizontal direction only (by a difference between the left and right eye’s perception of horizontal overlap of objects). Therefore stereoscopic content is created in the horizontal direction (e.g. with two camera’s next to each other, simulating our two eyes).
    As such, compressing vertically (half-OU) should do a better job at retaining stereoscopic information than compressing horizontally (half-SBS).

  20. Contrary to what I read the images look much better when my cursor is not hovering over them. When I hover my cursor over image #1 nearest neighbor I see stepping along all the lines and when I hover over the image using Bicubic Smooth it gets soft and looks out of focus. Am I reading it wrong? I’ve had the LG TV 55UB850T 4K UHDTV for about 6 mos and it’s incredible, I’m still discovering new things it’s capable of. I’m not a big fan of the way the remote uses a cursor to select and scroll through menus, but I’m getting used to it. The best thing is it won’t be obsolete any time soon, for once technology has to catch up to it. I’ve seen a few things in UHD, the picture blows my mind at 1080, I can’t wait til everything’s 4K.

  21. I have found out that half OU movies are more easy to watch. When the camera moves horizontally (which is usually the case in movies) half SBS gives a more fragmented video and gives me a headache, while half OU is smoother and easier to watch.
    Anybody experiences the same?

  22. thank you very much,
    excellent post, now I’m aware to what i must choice… with no doubt.
    cheers from France.

  23. Hello!
    Let me join to this very interesting discussion. We know now the SBS and OU in active 3D 1080p is a matter of much discussion. Some people say the SBS brings better experience and others people OU. So what better to choose?

    Still talking about 1080p, what if we want to display the image 4k in the active 3D? The answer which is better still not be so clear or maybe at this resolution, something changes? Personally, I think it is better suited SBS (1920×2160) than OU (3840x1080p). Although it may in what mode will display the image does not make any difference (the same situation like 1080p)?

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