LG 79UF770T and 5.1 Sound Issue

RussllW

Novice Member
LG 79UF770T and 5.1 Sound Issue

Good afternoon,

I'm hoping someone can help.

I have an LG 79UF770 UHD TV and a Marantz SR5007N AV Receiver.

HDMI ARC In on the TV connects to the HDMI out on the AV Receiver
Optical Audio on the TRV connects to Optical Audio in on the AV receiver.
All other devices Cable box (HDMI), DVD-R (Component), VCR (Component) and Blu-Ray player (HDMI) all connect to the AV receiver.

The issue I have is that when playing MP4 files from a USB memory stick (we have slow streaming speeds here) anything that is encoded with 5.1 AAC (at least) has no sound at all.

To test, I have just downloaded three versions of the one file.

1. A 400p (720x400) AVC video stream with 2 channel 256 kbps 48 kHz AAC LC audio that plays fine.
2. A 720p (1280x720) AVC video stream with 5.1 channel 637 kbps 48 kHz AAC LC audio that has no sound when played.
3. A 1080p (1920x1080) AVC video stream with 5.1 channel 637 kbps 48 kHz AAC LC audio that has no sound when played.

I've tested with just about every setting on both the TV and AV Receiver without success.

I think (but will go and confirm shortly) that 5.1 Blu-Ray discs are fine - well at least they have audio even if it is being down sampled but unless I convert the MPEG4 files to stereo I get no audio.

Any pointers welcomed.
 

next010

Distinguished Member
Any pointers welcomed.

LG's media player is not capable of decoding AAC 5.1 into stereo.

Get an box like this the Vero 4K+ it runs Kodi and can play most HD/4K formats, plug it into your receiver.
  • In Kodi settings->system->audio set number of channels to match your receiver for multi-channel PCM output e.g. 7.2
  • This will make Kodi decode the AAC 5.1 as PCM 5.1
If you have anything else that runs Kodi the same applies like Rasperry Pi using libreelec.

The alternative is demux the audio from the videos and convert into stereo or DD 5.1 then mux back into mkv/mp4 container. This tool can do it pretty quickly, just download it from the gdrive folder on his page, untick copy on the audio, set audio as AC3 and save as new file.
 
LG's media player is not capable of decoding AAC 5.1 into stereo.
Hmmm...

Even my old 2016 LG televisions media player is able to transcode 5.1 channel AAC into 2.0 channel PCM.

It's even able transcode 5.1 channel AAC into 5.1 channel Dolby Digital. Either of which can be passed via optical SPDIF or HDMI ARC to a suitable decoding device.
 

next010

Distinguished Member
Hmmm...

Even my old 2016 LG televisions media player is able to transcode 5.1 channel AAC into 2.0 channel PCM.

It's even able transcode 5.1 channel AAC into 5.1 channel Dolby Digital. Either of which can be passed via optical SPDIF or HDMI ARC to a suitable decoding device.

Yours would be WebOS 3.0 I imagine, searching his model says its WebOS 2.0, could predate when LG added AAC 5.1 decoding.

Can think of any other reason it wouldn't work.
 

RussllW

Novice Member
Hmmm...

Even my old 2016 LG televisions media player is able to transcode 5.1 channel AAC into 2.0 channel PCM.

It's even able transcode 5.1 channel AAC into 5.1 channel Dolby Digital. Either of which can be passed via optical SPDIF or HDMI ARC to a suitable decoding device.
That's what I expect but it seems the issue is with the LG Media player used for external media like USB flash drives as it apparently doesn't have the capability. I have confirmed that 5.1 is played successfully from other sources (Blu-Ray, Cable box & even the DVD Recorder) so it looks like I'll be adding some other device to play them or just keep converting them to stereo before putting them on the memory stick!
 

RussllW

Novice Member
Yours would be WebOS 3.0 I imagine, searching his model says its WebOS 2.0, could predate when LG added AAC 5.1 decoding.

Can think of any other reason it wouldn't work.
You are correct it is Web OS 2.0 and after a lot of searching it seems that the AAC 5.1 decoder was added with WebOS 3.x.

Pity really when the two much cheaper TV's in the house - an older Sony KDL70R550A and a newer Samsung UA55RU8000W can convert the 5.1 stream to Dolby Digital and play them fine.
 
Yours would be WebOS 3.0 I imagine, searching his model says its WebOS 2.0, could predate when LG added AAC 5.1 decoding.

Can think of any other reason it wouldn't work.
Even my 2012 and 2013 'pre-webOS' LG televisions are able to play files containing 5.1 channel AAC and output 2.0 channel PCM...
 

RussllW

Novice Member
Even my 2012 and 2013 'pre-webOS' LG televisions are able to play files containing 5.1 channel AAC and output 2.0 channel PCM...
See above - mine can too just NOT from the inbuilt media player when playing files from a memory stick. Try plugging one into yours (if the older ones have a USB slot) and see what happens.
 
See above - mine can too just NOT from the inbuilt media player when playing files from a memory stick. Try plugging one into yours (if the older ones have a USB slot) and see what happens.
I can confirm that my older Netcast TV's have no problems playing 'AVC+5.1 channel AAC' files muxed within .m2ts, mkv or .mp4 containers, from a USB flash drive, using the in-built media player...

EDIT: All my TV's 'Sound Out' options are set to 'Auto'...
 
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RussllW

Novice Member
I can confirm that my older Netcast TV's have no problems playing 'AVC+5.1 channel AAC' files muxed within .m2ts, mkv or .mp4 containers, from a USB flash drive, using the in-built media player...

EDIT: All my TV's 'Sound Out' options are set to 'Auto'...
Some of mine aren't. I know (at least) it's set to use Optical audio out so I might try removing the optical connection and see what happen s via HDMI alone.
 

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