AppleTV 4K > Plex converting MP4 into MKV?

[davidhose]

Server Version#: 4.91.2
Player Version#: 8.8.2

When looking in Tautulli, with all settings set to Maximum to allow for Direct Play on Apple TV 4K over internet, Tautulli shows that Plex is converting the container format from MP4 to MKV.

This seems extremely strange given MP4 is AppleTV’s preferred container format? I convert all of my media to MP4 and most files play just fine. All 1080p content works without a problem. This particular file is 2160p HDR10. Other 2160p HDR10 files work.

This particular file has an average video bitrate of 10.0Mbps and audio is AC3 384kbps. I’ve been able to successfully play a 2160p HDR10 file with an average video bitrate of 9.5Mbps and audio AAC 512kbps.

Does anyone have any ideas as to why Plex would be converting the container format to MKV which I then assume it is having to convert back to MP4 for the AppleTV to use? How can I stop it from doing this?

Any advice would be greatly welcomed.

Thank you

[nibbles]

The decision for the remux would be listed in your server log and/or the Plex ATV log.
Feel like rebooting, demonstrating, zipping, and attaching?

[davidhose]

Plex Media Server Logs_2022-09-25_13-42-36.zip (4.4 MB)
Here are the logs Hope this helps!

[davidhose]

I had a read through the logs myself and from what I can gather, Plex has determined that my bandwidth isn’t great enough to allow for this movie to play as the calculated bandwidth required is 37mbps and Plex is only willing to use 24mbps of available upload bandwidth. Therefore it made a decision to transcode. I’m still perplexed as to why it would go into MKV format… and why it shows as requiring 21.8mbps bandwidth (is that because the transcoded file would only require that?), and why everything is saying Direct Stream. @_@

[ChuckPa]

Sep 25, 2022 13:41:03.863 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode/Req#158b] We're going to try to auto-select an audio stream for account 157187905.
Sep 25, 2022 13:41:03.864 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode/Req#158b] Selecting best audio stream for part ID 54679 (autoselect: 1 language: en)
Sep 25, 2022 13:41:03.864 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode/Req#158b] We're going to try to auto-select a subtitle.
Sep 25, 2022 13:41:03.864 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode/Req#158b] Audio Stream: 112848, Subtitle Stream: -1
Sep 25, 2022 13:41:03.867 [0x7f8039f4fb00] DEBUG - [Req#1491] We're going to try to auto-select an audio stream for account 157187905.
Sep 25, 2022 13:41:03.868 [0x7f8039f4fb00] DEBUG - [Req#1491] Selecting best audio stream for part ID 214 (autoselect: 1 language: en)
Sep 25, 2022 13:41:03.868 [0x7f8039f4fb00] DEBUG - [Req#1491] We're going to try to auto-select a subtitle.
Sep 25, 2022 13:41:03.868 [0x7f8039f4fb00] DEBUG - [Req#1491] Audio Stream: 511, Subtitle Stream: -1
Sep 25, 2022 13:41:03.872 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode] MDE: Selected protocol http; container: mp4
Sep 25, 2022 13:41:03.872 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode] MDE: analyzing media item 54172
Sep 25, 2022 13:41:03.872 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode] MDE: The Invitation (2022): Direct Playing due to no transcode profile
Sep 25, 2022 13:41:03.872 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode] MDE: The Invitation (2022): DirectPlay
Sep 25, 2022 13:41:03.873 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode] MDE: The Invitation (2022): selected media 0 / 54172
Sep 25, 2022 13:41:03.873 [0x7f8036b81b00] DEBUG - [Req#1383/Transcode] Streaming Resource: Calculated bandwidth of 37922kbps exceeds bandwidth limit. Changing decision parameters provided by client to fit bandwidth limit of 24000kbps

The bandwidth limits which apply are:

1. Player requested quality level
   -or-
2. Internet upload speed (Remote Access)

This statement:

Changing decision parameters provided by client to fit bandwidth limit of 24000kbps

asserts the limit is on the server side.

[davidhose]

I told some lies to Plex and told it that my upload speed is actually 100Mbps (even though speedtest.net tells me it’s 28Mbps). This has completely resolved the issue and the file is now playing perfectly.

Seems the issue was just that my little Synology box is far too weak to handle conversion of a 4K file. Still some mysteries though, like why it was converting to MKV and why it was showing as Direct Stream when it was a conversion… however, it’s now resolved, so happy days.

PS- yes, I know that lying to Plex about my internet speed is likely to result in playback issues however ATV seems to buffer far enough ahead to counter it - so far so good anyway.

Thanks for your help @nibbles and @ChuckPa !