One episode won't load on Web Client, loads on Android App

[ghoul]

Server Version: 10.9.1, then 10.10.0
Running on Ubuntu Server 22.04 installed via package manager

First episode of GoT won't load on Web player in Firefox on Windows 10. Basically appears to be buffering slowly. This is a show I added ~12 hours ago. Tried a different episode and it played on Firefox. The first episode, that I'm having problems with, plays fine on the Android app over WiFi.

Frustrated while waiting I updated the JF server version, hoping it was a bug or "stuck".

The video actually has started playing. I guess it was converting the file for playback or something. I couldn't get it to play more than a second or two at a time at first. Now I can seek through any point in the video and it starts playing.

I'm hoping someone can tell me what to look for in logs that will tell me what was happening when it wouldn't play, so I can understand in the future. I tried grepping the remux logs for the show title but don't see a transcode for this title.

Server logs attached

[TheDreadPirate]

What are the hardware specs of both your server and your Windows 10 client? In the file name I see that it is AV1 + 7.1 OPUS. The AV1 part should play in Firefox, as long as your client hardware can decode it. But I see that it is being transcoded, on the CPU, to H264. The 7.1 OPUS may require downmixing since I am pretty sure most browsers support up to 5.1.

[ghoul]

Client:
Ryzen 5 3600
GTX 1070
32GB RAM

Server:
Xeon X5675
No discrete GPU
48GB RAM

I guess I was blind, but I now see where it was transcoding GoT. I couldn't find anything about 5.1 vs 7.1 Opus support for Firefox. I wonder if there's a log that indicates something like "Client reported X, will start transcode"

[TheDreadPirate]

Your client GPU does not support AV1 decoding. I'm wondering if that is why the video is being transcoded to H264.

If you look at the Jellyfin Dashboard, it will show you all the active sessions. Click on the "i" icon and it will tell you the playback method and why it is transcoding.

You can see the same on the click. Click on the gear in the bottom right during playback and click "Playback Info". It will list the transcode reason there as well.

[ghoul]

When playing other episodes of the same show it shows:
Playback Info
Player
Html Video Player
Play method
null
Protocol
http
Stream type
Video
Video Info
Player dimensions
1920x965
Video resolution
1920x1080
Dropped frames
302
Corrupted frames
0
Original Media Info
Container
webm
Size
871.2 MiB
Bitrate
2.5 Mbps
Video codec
AV1 Main
Video bitrate
2.1 Mbps
Video range type
SDR
Audio codec
OPUS
Audio bitrate
381 kbps
Audio channels
8
Audio sample rate
48000 Hz

In the dashboard it says:
The source file is entirely compatible with this client and the session is receiving the file without modifications.

When playing the first episode, again it appears to start transcoding again. I cannot see player controls, and the "i" does not appear for this client in the dashboard.

If I refresh I get player controls but we're still transcoding and cannot play past the first 1 second. Playback info does not report anything; I only see the X to close the playback info.
Dashboard "i" is now visible and reports: "The source file is entirely compatible with this client and the session is receiving the file without modifications."

[TheDreadPirate]

Are you using a reverse proxy? If so, did you setup websocket proxying?