TrueHD with Dolby Atmos 7.1 sound skipping (11Mbps audio bit rate)

Atmos TrueHD passthrough sound is skipping on certain spot in 4K .mkv file.
The skip is always on the same spot.
CoreELEC 9.2.0 stable and “9.2-nightly_20191025-Odroid_N2”, fresh clean install, produce the same skip.

Playing the file in VLC on Windows will not produce the skip.

Sample file (55MB): https://drive.google.com/file/d/1DNzrsbEuLWDuYHdXUpXq7E4lygUD8_1q/view?usp=sharing
There are 3 specific skips in this sample file.

Kodi Log: https://drive.google.com/file/d/1bMO05wfs5y086m_5lXTeQ1UgSg7nXcAw/view?usp=sharing

Could you please kindly fix this?
There are several more movies where this happens, and it’s very very annoying when it happened.

Thank you so much in advance!

Here is another sample file (73MB): https://drive.google.com/file/d/1ICEnUCOZS-FxYCm66CzSJQvlLHivr_Qo/view?usp=sharing
There is 1 skip in this sample file.

Kodi Log: https://drive.google.com/file/d/1SC60qOk8boTgWVdZZ4onwqHj-zF7fxTu/view?usp=sharing

Anybody tried it and got skips/drops too?

Yeah, i get the dropouts too, both on S905X and S922X. My AVR says it looses the signal when there is a dropout. Like it says it receive Dolby TrueHD Atmos 7.1 and when there is a dropout, the source signal is left blank. I’m wondering if this is related to the high audio bitrate, as both samples have a maximum audio bitrate of around 10-11 Mbps, which is fairly high.

Could you please DM me with the complete filename and mediainfo for both the files as it could be a issue with the encode? And please refer to all the samples you are having an issue with if there are more than the two provided

Sure, I’ll DM you the details.
I don’t think it’s because of the encode though, because the file played fine in VLC on Windows.

There are others, but I forgot the title and where it skips.
I recently watched these 2, so I remember where it happened.

Edit: I can’t seems to DM you… hmm…

I don’t think it’s an issue with the samples as they play fine on Windows as you say and if you disable audio passthrough and play them in PCM 7.1, you won’t get any stutter. So in the meantime, disable audio passthrough for samples which show identical stuttering issues until it gets solved :+1:

There’s a PR for Kodi with fixes on the way.

There’s a fix for buffer memory (or similar) and another for ffmpeg which is used for audio HDMI Passthrough.

Here’s a link to the Kodi PR:

Can you link the PR? I think I had this problem early on with a simple soundbar, with the box connecting to the TV and feeding the soundbar via optical.
I was never able to figure what the problem was. After switching to a more advanced soundbar (the old one died), and having HDMI 4K/HDR pass-through the soundbar, I don’t have this issue anymore.
This is why I suspected a crappy HDMI cable rather it being an actual problem.

I’ve tested three different HDMI cables where two of them are the standard Xbox One X and PS4 Pro HDMI cables, and all of them are able to play 80 Mbps 4K HDR10 content and 250 Mbps Jellyfish clip without any issues… So, I’m for that this is an issue with buffering regarding audio passthrough when playback of high bit rate audio files. Both movies have a uncommonly high bit rate for audio with average bit rate of around 7600 Kbps and peak at 9300 and 11300 Kbps. And if it was a HDMI cable issue, wouldn’t the issue persist when disabling audio passthough and using PCM 7.1? I mean, the sound quality is the same except the object oriented aspect with Atmos, so I think it should still stutter if it was the HDMI cable as the audio bit rate is the same

Yeah, that’s what I suspected too. Dropouts because of the HDMI cable.

But I’m using this beast: https://www.amazon.com/Monoprice-Commercial-24AWG-Speed-Jacket/dp/B005CAQODU
Look at that… The cable is as thick as the head…
Not only thick, it’s also very stiff and rigid. I didn’t know cable could be that hard to bend.
That 5ft 24AWG beast could probably pass HDMI 2.1 cert…

Are you sure that is the cable you are using? If so, I highly recommend to swap it out as it is 9 years old and therefore version 1.4… It’s probably not HDR10 capable and the max. transmission rate is 10 Gbps vs 18 Gbps for HDMI 2.0. Have you tried playback of samples which are 4K HDR10 60fps/Hz?

High bitrate dolby truehd (greater than 10Mbps) has always been a problem for Kodi. Looks like this development may now sort it out.

Yes, that’s the one I currently use.
I do have other HDMI 2.0 cables, but the quality is not as good as that one.

At 5ft, 24AWG is definitely overkill.
I’m fairly certain that this cable can even handle HDMI 2.1 (48 Gbps) just fine.
As long as the spec don’t add chips for active cable shenanigans…

I did test it with many 4K HDR10 60fps videos.
Also tested it with 250 Mbps Jellyfish video.
All played just fine.

The video bandwidth doesn’t matter, what matters is the resolution, bit depth, chroma and refresh rate.

Ah, gotcha.
I just tested it again with demo samples like in here: http://uhdsample.com/60fps/
Most of the samples showed 3840x2160p, 60Hz, 10-bit, YUV420, HDR10, BT.2020nc
They all played fine.

Btw, I got several of those thick Monoprice cables, some of the old one is even thicker, maybe 22AWG wires. I don’t think they sell the 5ft one at 22AWG anymore. It’s like old tube tv, they last a lifetime. :laughing:

Edit:
Found another sound skipping.
(88MB): https://drive.google.com/file/d/1Th8Q7S0LPl6HR_tNqYj3GQKfJu_Oa9Oc/view?usp=sharing
1 skip in the file. Just a sample to test with when the fix is applied.

Yep. I found a problematic one myself. Had dropouts almost every time the bitrate went over 11Mbps, and once even crashed Kodi. Hopefully the dropout fix will be available soon, and we’ll add those patches until it will be part of Kodi.

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However video bandwidth and the pixel rate/clock rate (HDMI 2 changes the relationship between the two at high baseband (*) bitrates) are intimately linked to resolution, frame rate, bit depth and pixel/chroma format. The higher the video bandwidth (and thus the bitrate at baseband) (audio is carried in video blanking on HDMI) the more demands are made on the HDMI cable. It’s not about thickness of the cable either - it’s about its performance at high frequencies.

I’ve had thick cables that fall over at 2160p60 4:2:2 12-bit on HDMI 2 and thinner cables that are fine at this video bandwidth.

(*) baseband bitrate = the uncompressed bitrate of video passing over the HDMI cable - not the heavily compressed HEVC/h.264 in the source file.