LG TV App buffering, but DLNA is fine

[LordOfThePigs]

Server Version#: 1.18.2.2029, Running on Synology DS918+
Player Version#: 2.1.3

Hello,

I’ve got a 4K HDR file with a bitrate of ~72Mbit/, and I’m trying to play it on my TV, but I’m having a few difficulties.

Here’s my setup:

• Plex Media Server is installed on a Synology DS918 NAS
• The TV is an LG OLED65C7
• PMS (on the NS) is connected to the network through Gigabit Ethernet.
• The TV is connected to the network through 802.11ac. The access point reports a connection speed of ~500Mbit/s (I had to do this because LG decided to cheap out and only include 100Mbit/s ethernet port…)
• The wireless network is capable of 200~250 Mbit/s real-world speed (as reported by my phone, I couldn’t find a reliable speedtest app for the TV)
• I also have a Chromecast Ultra hooked to the network on a Gigabit ethernet link.
• The TV is on the latest firmware version
• PMS is on version 1.18.2.2029

The file I’m trying to play is a ~60GB mkv that PMS reports as 4K (HEVC Main 10 HDR).

Given my setup, I have 5 different ways to play this file:

1. Chromecast it (Doesn’t work, because apparently chromecast Ultra doesn’t like the combination of HEVC + MKV + 4K + HDR)
2. Play it on the TV through the official Pley app (Doesn’t work. The video is not decoded correctly and only displays a bunch of multicolor boxes in one corner of the screen)
3. Play it on the TV through XPlay (Sort of watchable. The video is decoded correctly, but playback is interrupted for 3 seconds a couple times every minutes for buffering. This is extremely annoying)
4. Play it on my android phone. (Playback is perfect, no buffering but the screen is tiny…)
5. Play it on my TV through the Plex server’s DLNA function (Playback is perfect, no buffering, but the UI is not exactly friendly to use for the rest of the family).

Keep in mind that all clients I use are configured to use DirectPlay. PMS doesn’t support transcoding HDR videos properly so any transcoding makes the movie look like it was shot through 300 feet of fog.

Here are some conclusions I have drawn so far:

1. The Wifi connection is both fast enough and reliable enough.

I’ve tried multiple different Wifi setups on the TV and on the access point. No config changes made any real difference. IN all cases, the TV can play the file via DLNA on wifi, and the phone can play it via the plex app.

2. The file is not corrupted

Only the Plex App on the TV produced and mangled output. All the others played it fine.

3. There is something weird going on between PMS and the TV apps (Plex, XPlay) that doesn’t happen via DLNA

Both apps use the same HLS protocol to talk to PMS. When the stream is playing in both these apps, I can monitor the bandwith usage on my NAS. The bandwidth used in those cases is more or less stable around 7MB/s, with peaks around 7.5-8.0 MB/s (which is basically what you’d expect when playing a file with a bitrate of 72 Mbits/s).

However, when I play the file via DLNA, the bandwith usages starts with a big burst around 15-20 MB/s, then also stablizes somewhere around 7MB/s with occasional peaks around 15MB/s. I get the same bandwidth usage pattern when playing the file on the Plex app on my phone, which happens to be the only other player that works perfectly.

It looks like the DLNA player on the TV is able to stream the video data from PMS much faster than Plex’s own player+protocol combination. It seems that the DLNA player is properly buffering the video ahead of time, but that the plex/xplay player is not keeping a large enough buffer causing a pause in playback as soon as the effective bit rate rises a bit.

So my question is:

Ideally, what I would want it to be able to be able to play the video on either the Plex app or XPlay on the TV, does anyone know what I can do to make it work? I feel like I’ve exhausted my options.

[FordGuy61]

It sounds like the video is transcoding when using the LG Plex app.

Play the movie again with subtitles disabled. Also, choose a Dolby Digital or dts audio track. Do not choose TrueHD.

During playback, check the Plex Dashboard to see if the video and/or audio is transcoding. Login to PMS via Plex Web. Choose Activity -> Dashboard. If needed, expand what is shown in Now Playing by clicking on the gold rectangular icon on the right.

Please attach the Plex XML information for the movie. Save it as a text file and attach to your reply.

You want both the video and audio to Direct Play if possible. Transcoded audio puts little strain on the CPU, so it should not cause any issues if it happens. Video is a different beast. You want to avoid transcoding video, especially 4K, at all costs. The DS918+ does not have enough horsepower to reliably transcode 4K. Also, transcoded 4K HDR generally looks poor, with washed out colors, as Plex does not yet tonemap HDR to SDR.

Regarding the LG Plex app:

Enabling PGS or VOBSUB (image based) subtitles forces a video transcode.
SRT (text) subtitles will direct play.
However, if the audio is transcoding, enabling SRT subtitles forces a video transcode.

The LG Plex app will direct play Dolby Digital, Dolby Digital Plus (including w/ Atmos), dts, and AAC audio.
It will also direct play dts-HD MA audio, but it only uses the dts core. The “-HD MA” part is ignored.
TrueHD audio is not supported by the TV. Playing a TrueHD audio track forces an audio transcode.

[LordOfThePigs]

Nope the video is definitely not transcoding. It’s a HDR movie, and since plex doesn’t do h265 -> h265 transcoding, all transcoded HDR movies look like you’re looking at the characters through 300 feet of fog (plus my TV shows the little HDR badge).

I also tend not to use subtitles specifically because it most often forces transcoding.

The part that played fine had normal colors (for the few seconds it worked before getting mangled and scrunched up in the top left corner).

As I mentioned, everything is setup for direct play everywhere. No video transcoding happens, I may need to double check audio transcoding, but I’m not sure how audio transcoding would cause this kind of issue.