4k content buffering

General Discussions
1

Hi,

I’m having an issue with some 4k content buffering occasionally on my setup and I’d like some advice on how to track down what the issue is so that I can try to fix it. Not all 4k content will buffer, I’ve managed to play some 4k movies without any buffering issues at all.

First of this is my setup:

  • LG B7 tv running WebOS and using the XPlay client
  • TV connected to the network via an 100mb ethernet
  • PMS running on a Mac mini with 4gb ram connected via gig ethernet
  • Content stored on a Synology network drive connected via gig ethernet

So far I’ve ruled out any transcoding issues as I can play the 4k content and PMS is showing as “direct play”.

This is the info for a movie that I have had buffering troubles with:

Video Resolution 4K
Duration 2:43:27
Bitrate 54825 kbps
Width 3840
Height 2160
Aspect Ratio 1.78
Container MKV
Video Frame Rate 24p
Video Profile main 10

Codec HEVC
Bitrate 54185 kbps
Bit Depth 10
Chroma Subsampling 4:2:0
Color Primaries bt2020
Color Range tv
Color Space bt2020nc
Color Trc smpte2084
Frame Rate 23.976 fps
Height 2160
Level 5.1
Profile main 10
Ref Frames 1
Width 3840
Codec TRUEHD
Channels 7.1
Bitrate 4597 kbps
Language English
Audio Channel Layout 7.1
Bit Depth 24
Sampling Rate 48000 Hz
Title TrueHD Atmos 7.1
Codec AC3
Channels 5.1
Bitrate 640 kbps
Language English
Audio Channel Layout 5.1(side)
Sampling Rate 48000 Hz
Title DD 5.1 AC3

And this is the info for a movie that has played without any troubles:

Video Resolution 4K
Duration 2:15:46
Bitrate 19686 kbps
Width 3840
Height 1604
Aspect Ratio 2.35
Container MKV
Video Frame Rate 24p
Video Profile main 10
Title Original

Codec HEVC
Bitrate 18470 kbps
Bit Depth 10
Chroma Subsampling 4:2:0
Color Range tv
Color Space bt2020nc
Frame Rate 23.976 fps
Height 1604
Level 5.1
Profile main 10
Ref Frames 1
Width 3840
Codec EAC3
Channels 5.1
Bitrate 576 kbps
Language Français
Audio Channel Layout 5.1(side)
Sampling Rate 48000 Hz
Codec TRUEHD
Channels 7.1
Bitrate 7508 kbps
Language English
Audio Channel Layout 7.1
Bit Depth 24
Sampling Rate 48000 Hz

I’ve looked at the resource usage on the mac mini while playing a movie and the server is does not appear to be under much load on the CPU or memory. Does anyone have any ideas as to where the issue could be or how I could do some further investigations to work out what might be causing this?

Thanks

2

Gees…
Look at the bitrate difference between the one that plays and does not play…

Try lowering that bitrate a little.

3

Unless the Mac-mini has an i7-7700 processor (or better), and is using HW transcoding, you don’t have CPU power to transcode HEVC HDR to transcode it smoothly to H.264 (PMS does not transcode to HEVC) for streaming.

Also be advised, HEVC, when converted to H.264 for streaming, increases bit rate approx 1.5 - 2x . This as baseline, 50 Mbps of HEVC will expand to 75-100 Mbps. 100 Mbps video requires 120 Mbps of network bandwidth to transport it. 100 Mbps rated networking does not include the overhead required for TCP/IP and PMS protocol which is 15-20% added to the raw payload (video + audio + subitles) to transfer