[BUG] HDMI output doesn't work with MP4 files.

Hey guys,

So, I need some help here. I'm running KODI on the latest LibreELEC on Odroid C2.

In KODI, I have two audio output devices which I can select:

-ALSA: Default (AML-M8AUDIO, Analog)

-ALSA: AML-M8AUDIO, HDMI

Ideally, I always want to use my HDMI output because it then leaves all audio decoding tasks to my AVR (Denon s930h), which has a much better DAC (digital to analog converter) than my Odroid C2.

Really, I'm not being picky here. The difference in audio quality is actually quite noticeable.

The problem is, HDMI works most of the time, but it simply doesn't work with MP4 files.

When this happens, if I change the output to Default (Analog), the audio comes back, but with reduced quality, since it gets decoded by C2 instead of my AVR.

Anyway, my AVR should be capable of decoding pretty much anything, and I'm fairly sure it can decode MP4 files.

Do you have any idea about what's happening? Maybe I'm missing some other configuration?

Here's the log file. I try to play an MP4 movie via HDMI and there's no sound. Then I change to Default (Analog) and the sound comes back. Then change back to HDMI and no sound again.

hastebin

Thanks in advance for the help,

M.

Quote from blueribb

Similar thread here: Stereo passthrough issue in L9 and Odroid C2

Have you tried CoreElec ?

Similar issue, except that in my case I'm having problems specifically with aac/mp4 files. Other formats, stereo or not, work fine.

And no, I haven't tried CoreElec. Lost my emmc>micro sd adapter, so unless there's another way to install it remotely, I'm stuck with LibreElec. Tried to place its image inside the update folder and restart, but it didn't update to CoreElec.

Anyway, so far, I've found 3 workarounds, but none of them is ideal.

1-Play everything through the default/analog output. This doesn't affect passthrough signals, but plays music files through Odroid's DAC, which sounds considerably worse than my AVR's DAC.

2-Enable "stereo upmix". This makes aac/mp4 play, but will upmix everything that doesn't passes through, including my music files. Far from ideal, in fact, I'm yet to find any upmixing process that sounds good.

3-Enable "stereo upmix", reduce number of channels to 2, enable "Dolby Digital Transcoding". When you reduce the number of channels to 2, a new option called "Enable Dolby Digital Transcoding" shows up under "Passtrough" settings. This allows video files encoded with aac/pm4 to be properly decoded by the AVR...Again, the downside is that music files are still processed by Kodi; They're not really upsampled, since there are just 2 channels selected, but are still being unpleasantly processed.

To sum up, the problem boils down to playing music. Every one of the above workarounds "solves" the "video without sound" issue, specially option 3. However, in every one of them music quality is still being affected either by Odroid's DAC or Kodi internal processing.

If you ask me, this is a bug.

Quote from Da Flex

PS: It's a pretty old log from 2018.

What, my log? I've generated and uploaded it yesterday.

So, should I submit a bug report? I'm fairly sure this is a LibreELEC bug, since others have reported solving this issue by moving to CoreELEC.

I can confirm that CoreELEC doesn't have this issue.

I've started using it yesterday and it's working just fine.