360video-resolutions

Every production is quite different in scope, budget and schedule. However we do know that we are going to end up with a video of resolution and bitrate that is likely to be consistent. We’re discussing the best outputs for platforms as it stands in this post.


 

We refine our workflow job by job, seeking for the best quality versus speed equation to deliver suitable image for each job. There are three elements to this – resolution, bitrate and codec. File size is also important depending on logistics.

Resolution

Regarding resolution, we know that videos for 360 need to be 4K minimum. As 360 players wrap an equirectangular video into a sphere, the viewer is only going to see a small section of that video. At 4K UHD, we end up viewing a window of about 1.3K resolution.

Having a master resolution of 1920×1080 HD results in about 370-pixels of data, which is two thirds of SD. Far too soft to be comfortable or watchable in our opinion.

8K resolution videos would be ideal, rendering down to around 2K window which is equivalent of the HD images general audiences have gotten used to. However 8K is not viable either as a workflow on any reasonably priced computer system, or more importantly viewable on any mass-market VR device. When mobile phones can play 8K video smoothly, then this format will be worth attaining, however right now 8K is only available on youtube and very few have the capability of streaming and watching such a high resolution.

4K Output

At the moment, we often work to one of the following resolutions:

  • 4096×2048 – This is a nice maximum 4K ‘cinema’ format which at 2:1 aspect plays comfortably on Samsung phones, Youtube and elsewhere.
  • 3840×1920  – A simpler UHD resolution. In the past we would often work to this resolution as it is simple and work consistently.
  • 3840×2160 – Our current quick turnaround master, this resolution features 10% image improvement over the 3840×1920 option. Video players on Youtube and Samsung scale this 16:9 aspect to fit perfectly within their players.
  • 4096×2160 – We have been testing this resolution lately. It seems it cannot be scaled on Samsung GearVR or Youtube at this time due to its unusual aspect ratio. If this aspect gets programmed into the player platforms, it will become our standard resolution export due to the higher number of pixels.
Resolution Aspect Pixels
4096×2048 (4K Cinema) 2:1 8,388,608
3840×1920 (UHD) 2:1 7,372,800
3840×2160 (Quad HD) 16:9 8,294,400
4096×2160 (4K HD) 1.9:1 8,847,360
7680×4320 (8K UHD) 16:9 33,177,600
8192×4096 (4K Cinema) 1.9:1 33,554,432

In terms of 4K master, we can see that 4K cinema is 12% sharper than UHD. However it is only 1.2% sharper than Quad HD which we find a comfortable size for our videos.

We need to look at 4096×2304 which is a 16:9 resolution 4K. If this is supported by Youtube and Samsung GearVR, it may be an excellent master format – we need to do more testing. It is possible this is above the maximum supported resolution on the S7, but the upcoming S8 may be able to support this greater number of pixels.

8K is of course a huge leap forwards being 4x the quality of resolution.

It is also worth noting that for Oculus rift a full higher resolution can be supported. 4096×4096 is suggested as the best format at this time for a powerful PC.

Bitrate

We tend to keep our bitrate during post workflow to 100Mb/s (100,000 kbps). This is a reasonable compressed data rate which doesn’t have too much effect on the video. Some iMac 5K’s struggle with this rate and some are fine. Upgraded RAM helps, or working with a PC with good specs including a healthy GFX card.

Often we will then master to 75Mb/s for Samsung GearVR and Youtube at the end of the workflow.

With non-mp4 codecs, a bitrate is greater as standard but the codecs are more stable. Prores 4K UHD 422HQ 734Mb/s or 4444 at 1100Mb/s are great to stick to for workflows. The problem is that most of our current camera systems capture in MP4, often at 60Mb/s so other than trying to reduce the amount of compression during re-renders, prores is somewhat redundant from the start. We do tend to keep it in prores after stitch through the pipeline right up to the master render which is finally output often as MP4.

Codec

H.264 is the standard video codec supported. We use this for Youtube, Facebook, Desktop Players.

H2.65 is the best codec for any GearVR displays so a version is always rendered to this codec for this platform on every project.

Prores is only used during the workflow at this time as it is not supported in any players. We don’t generally work with cineform or uncompressed due to the larger data sizes at this time.

Delivery Resolutions

  • Samsung GearVR (S7) – 3840×2160 is the optimally supported size (otherwise 4096×2048) at 60-75Mb/s in H.265
  • Youtube – 4096×2048 at 100Mb/s in H.264
  • iOS cardbaord – 1920×1080 30Mb/s in H.264
  • Facebook – 4096×2048, 50Mb/s in H.264 (max file size 1.75gb)

We continue to refine our workflow and master outputs to squeeze the best image quality we can onto the delivery platforms. The sooner we get 8k supported platforms, the better.