Video position on frontend is behind by one update

[hyperionteam-msft]

When calling mixer.display.position() you appear to get the old (e.g. n-1th update) video position. The behavior on frontend is different from in miix.

Using position.subscribe() appears to always provide the correct value, event though position() doesn't.

Repro steps:

Frontend at position A
Call mixer.moveVideo(B)
Call mixer.display.position() => returns A
Call mixer.moveVideo(C)
Call mixer.display.position() => returns B

[gostay]

I can confirm this issue is still here, only it also seems to be wrong in the subscribe callback (in the position argument provided).

Currently working around it by calling moveVideo twice.

[gostay]

Unfortunately, in my experience there's even more weirdness going on here, so I want to add some more details:

• I get multiple inconsistent calls to my subscribed position callback. I get more calls than expected, including sometimes the same values several times in a row.
• right after my first moveVideo call, I generally get incorrect values
• until I trigger another moveVideo call

All of this varies based on

• which platform the participant experience is running on
• whether I've made a second call to moveVideo
• whether I waited for a moment before making the second moveVideo call (I think!)
• whether the Game Client is running already when the participant first arrives in the stream
• browser (unique weirdness on Edge so far)

For instance, only one call to moveVideo seems to be necessary in Chrome, but only if I arrive after the GC has started.

None of this is reproducible in the CDK, so this is all my experience from uploaded bundles.

Ideally, I'd only need to call moveVideo once, and any call after my moveVideo call would have the right values.

I think this is an important thing to fix. The inconsistency and difficulty in debugging and working around this (just calling moveVideo twice in a row doesn't cover everything) has made it a painful thing to address, and I expect any developer trying to position their UI relative to the video will run into this pain.

---

Some details from debugging sessions:

Every moveVideo call below is being made with these arguments:

mixer.display.moveVideo({
top: '15%', // leave room for our UI above that
bottom: 0,
left: 0,
right: 0,
});

---

Web (Chrome)

The stream is running, the web page open and refreshed, but no game client yet.
then launch game client.

My subscribed position handler gets called once early on:

|mixer poshandler: position:
| 0,208.375 708 x 398.25

(I don't really care about that value, because I haven't called moveVideo yet)
My code eventually calls moveVideo after the app and mixer have loaded, and I get:

|mixer poshandler: position:
| 8,212.875 692 x 389.25
|mixer poshandler: position:
| 8,212.875 692 x 389.25

This is, unfortunately, incorrect. The y value is wrong.
So, I trigger another moveVideo call, and...

|mixer poshandler: position:
| 8,274 692 x 389.25

That one is correct in all values.

---

Now let's try minimizing and maximizing interactive controls, with the GC still running.
My app gets restarted, and I first get this call, like before, which is fine:

|mixer poshandler: position:
| 0,208.375 708 x 398.25

And then my code eventually calls moveVideo, and I get:

|mixer poshandler: position:
| 8,212.875 692 x 389.25

That's incorrect. But I don't manually try to retrigger it... in a moment I get 3 more calls, all correct:

|mixer poshandler: position:
| 8,274 692 x 389.25

|mixer poshandler: position:
| 8,274 692 x 389.25

|mixer poshandler: position:
| 8,274 692 x 389.25

So, it's weird that starting the GC after the participant is connected to the stream results in different values
than restarting the participant experience.

---

XBOX:

(some of the numbers below are rounded for clarity)

stream running, no GC running.
open my stream in mixer on Xbox.
launch GC.

participant connects, and while it's not visible, it does make move calls and gets position events:
| handler position:
| 465,0 0x0

|calling moveVideo

| handler position:
| 2.2,-520 924x520

I of course can't interact until I hit the interact button, so I don't care about those values yet.
I hit the interactive button now, and I get more callbacks:

| handler position:
| 2.2,-520 924x520

| handler position:
| 2.2,0 924x520

These values are wrong (too wide) so I manually trigger another moveVideo,
and I get one call back, which is finally correct:

| handler position:
| 71.6, 78 785x442

On Mobile, I think I've seen a surprisingly long series of callbacks before, but then I turned off my subscription on mobile because we don't position our mobile UI based on player position.

---

EDGE specifics?

In edge, I somehow first get the correct values and then suddenly incorrect ones. :(

|mixer poshandler: position:
| 93.90001085069445,124.69999694824219 1147.199978298611 x 645.2999877929687

|mixer poshandler: position:
| 344.8500061035156,124.69999694824219 645.2999877929687 x 645.2999877929687

one more manual request after this gives me 1147 x 645 again, which is correct.