pulseaudio HDMI audio output only works with some TVs (Ubuntu 18.04)

Question

I have a HP EliteBook 745 G4 running Ubuntu 18.04 and I have a DisplayPort to HDMI cable connected to a 50" ONN non-smart TV. With this combination when I fire up pavucontrol I see two output types, "Built-in Audio Analog Stereo" and "Built-in Audio Digital Stereo (HDMI 3)" and I am able to use mpv to play a video file where I can select the HDMI audio output in pavucontrol to get the sound output to go to the TV.

However recently I have been struggling to get the same thing working at another location where there is a Samsung 75" smart TV (model # QN75Q80AA). When I go there with the exact same laptop and DP to HDMI cable, the only audio output that shows up in pavucontrol is the "Built-in Audio Analog Stereo". The video displays just fine to the TV but nothing I do will get the additional digital audio output selection in pavucontrol to appear.

Since it works at my house with the non-smart TV, with everything else being the same I have to think there is some unknown difference between the two TVs that is affecting the ability for Ubuntu to see the Samsung TV as a valid digital audio output.

Anyone have any suggestions as far as a solution or perhaps can suggest some tests that I can perform to narrow down the possible causes?

Just in case anyone is interested or feels that it might help answer my question the mpv version I am using is:

~$ mpv --version
mpv 0.34.0-563-g806dddc7d9-dirty Copyright © 2000-2022 mpv/MPlayer/mplayer2 projects
 built on Thu Nov  3 11:47:36 EDT 2022
FFmpeg library versions:
  libavutil       57.40.100
  libavcodec      59.51.101
  libavformat     59.34.101
  libswscale      6.8.112
  libavfilter     8.49.101
  libswresample   4.9.100
FFmpeg version: N-108921-g0957d62fb0

and the command syntax I am using with mpv is:

~$ mpv --audio-device=pulse/alsa_output.pci-0000_00_1.1.hdmi-stereo-extra2 ./Videos/Tour.de.France.2022.Stage.01.720p.h264-NX.mkv 

Since I posted this question I have gone back to the other location with the Samsung TV and tried various different HDMI ports on the TV since some are labeled as "HDMI" but one is labeled as "HDMI (eARC)" but connecting to different HDMI ports seems to have made no difference.

While I was there I also ran the command "pactl list" and redirected the output to a file so I could compare this output with output from the same command at my home office where the ONN TV works fine.

I found there were definite differences in this pactl output from one location to the other but I still have no clue what is causing it or how to fix the problem.

With the ONN TV where sound works fine I see two Sinks listed in the pactl output:

Sink #0
Name: alsa_output.pci-0000_00_01.1.hdmi-stereo-extra2

Sink #1
Name: alsa_output.pci-0000_00_09.2.analog-stereo

and two cards are listed:

Card #0
Name: alsa_card.pci-0000_00_01.1
        alsa.card_name = "HDA ATI HDMI"
Profiles:
        output:hdmi-stereo-extra2: Digital Stereo (HDMI 3) Output (sinks: 1, sources: 0, priority: 5200, available: yes)
        output:hdmi-surround-extra2: Digital Surround 5.1 (HDMI 3) Output (sinks: 1, sources: 0, priority: 100, available: yes)
Active Profile: output:hdmi-stereo-extra2

Card #1
Name: alsa_card.pci-0000_00_09.2
       alsa.card_name = "HD-Audio Generic"
Profiles:
        input:analog-stereo: Analog Stereo Input (sinks: 0, sources: 1, priority: 60, available: yes)
        output:analog-stereo: Analog Stereo Output (sinks: 1, sources: 0, priority: 6000, available: yes)
        output:analog-stereo+input:analog-stereo: Analog Stereo Duplex (sinks: 1, sources: 1, priority: 6060
Active Profile: output:analog-stereo+input:analog-stereo

but at the location with the Samsung TV with no sound I only see one Sink listed:

Sink #0
Name: alsa_output.pci-0000_00_09.2.analog-stereo

but there still are two Cards listed:

Card #0
Name: alsa_card.pci-0000_00_01.1
       alsa.card_name = "HDA ATI HDMI"
Profiles:
        output:hdmi-stereo-extra2: Digital Stereo (HDMI 3) Output (sinks: 1, sources: 0, priority: 5200, available: no)
        output:hdmi-surround-extra2: Digital Surround 5.1 (HDMI 3) Output (sinks: 1, sources: 0, priority: 100, available: no)
        output:hdmi-surround71-extra2: Digital Surround 7.1 (HDMI 3) Output (sinks: 1, sources: 0, priority: 100, available: no)
Active Profile: off

Card #1
Name: alsa_card.pci-0000_00_09.2
        alsa.card_name = "HD-Audio Generic"
Profiles:
        input:analog-stereo: Analog Stereo Input (sinks: 0, sources: 1, priority: 60, available: yes)
        output:analog-stereo: Analog Stereo Output (sinks: 1, sources: 0, priority: 6000, available: yes)
        output:analog-stereo+input:analog-stereo: Analog Stereo Duplex (sinks: 1, sources: 1, priority: 6060, available: yes)
Active Profile: output:analog-stereo+input:analog-stereo`

So at the location with the Samsung TV with no audio output the HDA ATI HDMI card has no active profile and with the ONN TV with the working audio output the HDA ATI HDMI card does have an active profile.

This is all great information but I still do not understand WHY this is happening with the Samsung TV.

Answer 1

Today I used a different type of cable to connect from the displayport of the laptop to the HDMI input on the TV and now sound works! Yahoo!

The original non-working cable was a single cable I got off of ebay for around $10 for a 10ft cable that when directly from the DP connector to HDMI on the other end.

The other cable I tried that ended up working was a regular HDMI to HDMI cable that plugs into a short pigtail conversion cable that went from DP to HDMI.