Media 360 Image page type - 2 questions about image size

Hi everyone,

Q1) Please can you let me know if there is a file size limit for 360 image upload to the Media 360 Image page type?

I have used an image from the site mentioned at the Xerte Conference March 2021. pixexid.com/search/360%20panorama

I notice that the size of the 360 image from the site is 1.14MB and pixels 6000 x 3000.

Q2) How does this very large image display and play on a mobile phone and how much bandwith does it require to display smoothly?

I know that large images can be slow to load on a device if the bandwith is low or Wifi internet connection is poor.

Is there a risk that the 360 image will not appear at all for those folk with problematic bandwith and Wifi?

I am particularly concerned about end-users with 'pay as you go' phones, as slow load of an image will result in cost implications for the end-user on pay as you go mobile phone for example.

Thanks in advance for any information about this.
Best regards
Anne

1: The server your Xerte install is on will have a maximum file size that can be uploaded - there's no additional limit specific to the 360 page.
2: I can't give you figures on this but it shouldn't be any more problematic for people than, for example, watching a video within a Xerte project would be

Hi Fay,

Thank you for the information which is reassuring.

Best wishes
Anne

Hi Anne
you and I have discussed image size before and I suggested you watch the recording of my presentation about images from Xerte21.
Whether for 2d images or 360 images it isn't as simple as having or stating or recommending a fixed size both in terms of image pixel dimensions and/or file size and never will be as there are too many factors and considerations at play.
In addition there's no one size fits all in terms of mobile device - with different platforms and different models having different constraints. Some examples and further comments:

I have a high quality 360 image made with my DSLR the native dimensions of which are 16384px x 8192px. Saved as a jpg at 100% quality the file size is 126MB. This plays fine on my laptop with a large 4k monitor attached but is not a combination of pixel dimensions and file size I would use or recommend in a real project especially not one where I need mobile compatibility too. However the reason I say that isn't necessarily because of file size because I can save the same image as a jpg at the same pixel dimensions but at 50% quality and the file size is then reduced to only 6.64MB and you would have to look really hard to spot any quality difference. So the pixel dimensions and file sizes for this particular image are:
16384px x 8192px saved as 100% quality = 126MB
16384px x 8192px saved as 50% quality = 6.64MB
It's also important to be aware that different images of the same pixel dimensions may result in larger or smaller file sizes depending on the contents of those images. e.g. a darker copy of this image with less details becomes only 4MB when saved at 50% quality. The software used to save resized copies can also impact the results too.

I know that the maximum width of a single 360 image from Xerte to display on my iPhone 7 (and iPad Pro) is currently 8192px. This isn't a Xerte specific limit but a limit of the model and/or OS and/or code library we use. There may be other 360 playback engines that play larger images than this on the same mobile devices but that's not really relevant here. So at the moment from Xerte anything larger will play fine on a desktop/laptop but will not play on my iPhone or iPad Pro. This means potentially you could say that the maximum recommended pixel dimensions of a single 360 image is: must be no wider than 8192px.
However I don't know if the considerations and constraints apply to more recent iPhones or iPads or newer OS versions or other platforms and models etc. You could follow the no wider than 8192px guidance but it's still a good idea to check with users and their different mobile devices.
If I save a copy of this image reduced to 8192 x 4096 at 100% quality the file size is now 4.25MB.
If I change the quality to 50% the file size is now 3MB.
Whatever images you use when the user first views the 360 page the image(s) will download and be cached on the device/browser used. For larger images/files sizes that can't load instantly because of slower bandwidth etc the page will display a progress bar.
When they revisit if the image(s) is still cached then loading will be more or less instant.

BTW Another point to note is that in more recent Xerte code (which will be in the next release possibly in March) we have added an additional option to use Cubemap versions of the single 360 images. This means that rather than a single large 360 image of say 4MB what is uploaded is 6 squares that each may be only 400kb. So this means that loading of larger panoramas is much quicker however the conversion to Cubemap will need to be done before uploading to Xerte, either with the software that comes with your 360 camera or with 3rd party or online conversion tools. We may be able to provide some guidance about this in our release notes when the release is made available but you can search for and read up about Cubemap images in advance if interested.

HTH
Ron

Hi Ron,
Thank you so much for your detailed reply with a wealth of information, and i will read it through and learn.
Best wishes
Anne