[SOLVED] A /V Synchronization Problem

business_kid · 10-07-2022, 04:56 PM

I'll start this by saying it could possibly be a dud video, but I tried to watch one of a series last night in VLC. The video froze but the sound carried on.

So I tried mpv. That went better, but I couldn't find my place without upsetting it. If I made the screen small, paused for a while, and then started play, things would synchronize eventually. The video would start silently, then the sound would come in. But I got these errors on STDOUT

Code:

[vo/x11] Warning: this legacy VO has bad performance. Consider fixing your graphics drivers, or not forcing the x11 VO.

and the other one says

Code:

Audio/Video desynchronisation detected! Possible reasons include too slow
hardware, temporary CPU spikes, broken drivers, and broken files. Audio
position will not match to the video (see A-V status field).

I have a RazPi 4B @1.5Ghz, an early model, running slarm64-15.0. VLC is version 3.0.16, and I don't know what the dependencies are so I can't pass version numbers. But they're all 15.0 or later IIRC.

I got video advice previously here, implemented it, and obeyed rule #1

Quote:

If it works, don't fix it!

Any ideas or diagnostic tests welcome. The videos are hdmi, 720 or 1080p h264, other ones work fine but I've had issues with a number of random videos recently.

Emerson · 10-07-2022, 07:05 PM

Both VLC and mpv have several options for video output, you have tried all of them?

sndwvs · 10-08-2022, 03:12 AM

Quote:

Originally Posted by business_kid

I'll start this by saying it could possibly be a dud video, but I tried to watch one of a series last night in VLC. The video froze but the sound carried on.

So I tried mpv. That went better, but I couldn't find my place without upsetting it. If I made the screen small, paused for a while, and then started play, things would synchronize eventually. The video would start silently, then the sound would come in. But I got these errors on STDOUT

Code:

[vo/x11] Warning: this legacy VO has bad performance. Consider fixing your graphics drivers, or not forcing the x11 VO.

and the other one says

Code:

Audio/Video desynchronisation detected! Possible reasons include too slow
hardware, temporary CPU spikes, broken drivers, and broken files. Audio
position will not match to the video (see A-V status field).

I have a RazPi 4B @1.5Ghz, an early model, running slarm64-15.0. VLC is version 3.0.16, and I don't know what the dependencies are so I can't pass version numbers. But they're all 15.0 or later IIRC.

I got video advice previously here, implemented it, and obeyed rule #1

Any ideas or diagnostic tests welcome. The videos are hdmi, 720 or 1080p h264, other ones work fine but I've had issues with a number of random videos recently.

this seems to be due to the specific encoded video with its settings and since everything is decoded by the software this problem occurs and overclocking the cpu can help.

business_kid · 10-08-2022, 04:12 AM

I could overclock, but I've the earlier 4B brfore they improved the power supply. If I try for 2.0Ghz, what sort of "overvolts=" setting would I need? Can I even use the overvolts adjustment in config.txt? I'm on the early firmware that allows usb boot. I know I'd have to work up gradually. But I can do that fairly painlessly by overclocking while booting on the SSD, and simply having a standard MMC card handy for when I inevitably screw up.

When you say 'it's all done in software', we're talking the swrast driver here, aren't we? That's bad.

Here's an idea: Could I run a video like this through ffmpeg to make something useful of it?

sndwvs · 10-08-2022, 04:29 AM

Quote:

Originally Posted by business_kid

I could overclock, but I've the earlier 4B brfore they improved the power supply. If I try for 2.0Ghz, what sort of "overvolts=" setting would I need? Can I even use the overvolts adjustment in config.txt? I'm on the early firmware that allows usb boot. I know I'd have to work up gradually. But I can do that fairly painlessly by overclocking while booting on the SSD, and simply having a standard MMC card handy for when I inevitably screw up.

When you say 'it's all done in software', we're talking the swrast driver here, aren't we? That's bad.

Here's an idea: Could I run a video like this through ffmpeg to make something useful of it?

programmatically, this means that SoC decoding blocks are not used.
mpv is already using ffmpeg.

I overclocked to 2147

Code:

# Turbo mode: 0 = enable dynamic freq/voltage - 1 = always max
force_turbo=0
# Start in turbo mode for 30 seconds or until cpufreq sets a frequency
initial_turbo=30

over_voltage=6
arm_freq=2147

business_kid · 10-08-2022, 06:21 AM

I'll try that overclocking - maybe 2Ghz max. I've the Flirc case, no fan.

sndwvs · 10-08-2022, 06:38 AM

Quote:

Originally Posted by business_kid

I'll try that overclocking - maybe 2Ghz max. I've the Flirc case, no fan.

I also have a simple aluminum radiator in size SoC.

business_kid · 10-08-2022, 09:18 AM

Quote:

Originally Posted by sndwvs

I also have a simple aluminum radiator in size SoC.

If you paint it matt black it keeps the cpu cooler by radiating the heat better. It's physics. Thermal models are compared with a a black body radiator.

Emerson · 10-08-2022, 09:56 AM

Quote:

Originally Posted by business_kid

If you paint it matt black it keeps the cpu cooler by radiating the heat better. It's physics. Thermal models are compared with a a black body radiator.

Not really. The difference between white and black radiator efficiency is 1% and it is lost when you put a layer of paint on your radiator because it acts as insulator. Besides, to gain this 1% the radiator must be black in infrared range of lightwaves, this is something human eye cannot see. LOL

business_kid · 10-08-2022, 10:10 AM

Quote:

Originally Posted by sndwvs

programmatically, this means that SoC decoding blocks are not used.
mpv is already using ffmpeg.

I overclocked to 2147

Code:

# Turbo mode: 0 = enable dynamic freq/voltage - 1 = always max
force_turbo=0
# Start in turbo mode for 30 seconds or until cpufreq sets a frequency
initial_turbo=30

over_voltage=6
arm_freq=2147

OK, I'm overclocked with "over_voltage=5" & "arm_freq=2000". No problems, but no improvement. I'm still getting the same errors. It seems mpv freezes one stream (video or sound) until the other catches up, and then synchronizes them. I'm not sure what vlc is doing. I tried cvlc in a terminal and trapped these errors

Code:

[h264 @ 0x7f8cce9370] co located POCs unavailable
[h264 @ 0x7f8cce9370] co located POCs unavailable
[h264 @ 0x7f8cc5c6f0] mmco: unref short failure
[h264 @ 0x7f8ccee410] co located POCs unavailable
[h264 @ 0x7f8cc5c6f0] co located POCs unavailable
[h264 @ 0x7f8cc5c6f0] co located POCs unavailable
[h264 @ 0x7f8cce40a0] mmco: unref short failure
[0000007f8cde6480] avcodec decoder error: more than 5 seconds of late video -> dropping frame (computer too slow ?)
[0000007f8cde6480] avcodec decoder error: more than 5 seconds of late video -> dropping frame (computer too slow ?)

business_kid · 10-08-2022, 02:05 PM

Marking this solved. It's the video. I tried it on my 6 core 3.5GHz Ryzen with a serious video card, and it's worse!