Some time after changing my HTPC from RPi3 (which is now an octoprint server) to RPi4 I discovered that some of my older video files have a very choppy (jerky?) sound. All the problematic files are TV-rips and they play fine on PC with VLC. The VLC shows the H264 - MPEG-4 AVC (part 10) as video codec and MPEG Audio layer 1/2 (mpga) as audio codec. The display is an old Panasonic plasma TV connected via HDMI.
The problem is not audible for first ca. 30 - 90 seconds, then it starts to increase, pause/playing the video helps for the same time again. Video playback is smooth all the time.
System information shows CPU utilization up to 40%, the temperatures are quite low. I have tried to enable or disable audio passthrough without any observable change.
I'd be grateful for any ideas.
Choppy mpga audio at RPI4
- stevie_256
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October 9, 2020 at 10:23 PM - Thread is Unresolved
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- Official Post
Try this.
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Try this.
Thank you, but that unluckily did not help (or change anything)...
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- Official Post
Thanks for testing. Next approach: Convert to MKV (by using mkvtoolnix for instance).
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Good Day. The situation is the same: RPI4 sound stutters (by the way, the previous RPI3b also went to octoprint;). The sound problem appears only with the AAC audio codec (TV PVR, TV recordings on YouTube) Other audio codecs without problems... Try switching libreelec mode from 60Hz to 24Hz. I now have 1920x1080p 24Hz .. There are no problems with the sound, but the interface is very freezing:(
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Upd: The problem is also observed with the mp3float sound track ... It is sad that it is difficult to watch a movie with dynamic scenes at 24Hz. Maybe there is some solution? There was no such problem on RPI3. advancedsettings.xml created. Tried downgrading from 9.2.3 to 9.1.502
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Thanks for the hint. Da Flex. I have RPI4B with 2Gb RAM, I tried to write it in config.txt> total_mem = 1024 ... Absolutely nothing has changed
gpu_mem = 320.If set 24Hz in the system display settings (as I wrote above) there really are no problems..
In principle, not so bad, but want it better
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At the 2GB variant, this result was expected. I guess the data bus is too slow for 60Hz plus AAC audio at the moment. Wait for optimization updates.
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If set 24Hz in the system display settings (as I wrote above) there really are no problems..
Maybe you can keep the original HDMI mode, and just switch de-interlacing off: Click!
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de-interlacing is disabled for all videos. Hardware acceleration is switched-off. Nothing changes. However, here's an interesting thing there are no problems with sound in bluetooth headphones. This is a clear HDMI problem .. Maybe, even the HDMI-MicroHDMI adapter is cheap. Maybe the TV is cheap (unnamed). I am switching temporarily back to RPI3 (it is really problem-free)
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de-interlacing is disabled for all videos. Hardware acceleration is switched-off. Nothing changes. However, here's an interesting thing there are no problems with sound in bluetooth headphones. This is a clear HDMI problem .. Maybe, even the HDMI-MicroHDMI adapter is cheap. Maybe the TV is cheap (unnamed). I am switching temporarily back to RPI3 (it is really problem-free)
Thanks again for the feedback! Can you check the standard of your HDMI cabling please? It has to be conform to HDMI 2.0 or 2.1. Otherwise it could be too slow for 4K. It's a common mistake of RPi3 -> RPi4 switchers not to update the HDMI cabling.
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This is a miracle=) Replacing the HDMI cable with version 2.0 solved the problem (at least in 2 hours of testing..)... But, this is very strange, because the TV is not 4K, and definitely does not have an HDMI version higher than 1.4 (no specification) .. How can this be? I probably don't understand something. Anyway, thank you so much Da Flex for your support! And good day!
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- Official Post
Anderssen Well, christmas is the time of miracles
. You're right, on a non-4K device a 1.4 HDMI cable should be fine. Those 2.0 / 2.1 HDMI cables have better shielding, so I think that did the trick for you. I'm happy that we finally solved it. 
