Swapping between HDMI and CRT sound+image issues.

[M75]

Hi, first time poster.
Pi Model or other hardware: 3B+
Power Supply used: Official 2.5A Powersupply
RetroPie Version Used: 4.4 Built From: (Pre made SD Image on RetroPie )

I have set up a RetroPie using my computer monitor via HDMI, then I moved over to my old CRT via the official Cable. But what happened was that the audio was not working properly. I searched around and found the troubleshoot guide, which I followed. To no avail. I installed a fresh image and booted for the first time, never connecting a HDMI cable. The Pi sent both audio and video over correctly to the TV, I didn't even have to make any changes in the settings. What does that mean? Do I have to maintain two SDCards for HDMI, one for CRT? Popping the already and properly set up SD Card in, I don't get a good Image, everythings distoreted, Audio sounds like in a submarine and every emulator plays at half speed. Popping the SD Card in with the image that never got connected to HDMI, everything looks good. Aspect Ratio and audio fit, framerate is normal.

Can I achieve that nice image via Composite on my CRT by changing one setting.

Which config files should I provide for this issue?

[A Former User]

Hi, try this.
I had similar slowdowns when using the official composite cable, I fixed it with the following.
With the Pi switched off. Put your SDCard in your PC, ignoring the error warnings (assuming you're using Windows), and you can access the boot partition.
Look for config.txt, and open it preferably with a decent text editor - I use Notepad++, I think notepad might be ok. Add the following line to the end of the file and save it.

audio_pwm_mode=0

That fixed the slowdowns, and the audio was much better. Hope that helps.

[M75]

Yes! That did fix it. Thank you very much, that one was causing headachs.

I searched multiple documentation sources for this issue, but didn't find it here https://www.raspberrypi.org/documentation/configuration/config-txt/
nor here
https://github.com/RetroPie/RetroPie-Setup/wiki/Sound-Issues

I searched for audo_pwm_mode to find further documentation, but I don't see alot of issues being discussed about this.

As far as my understanding goes, this has something to do with sdram frequenzy?
https://github.com/Hexxeh/rpi-firmware/issues/172#issuecomment-370781380

So going back to HDMI I'd have to remove/comment audio_pwm_mode=0

[Clyde]

@m75 said in Swapping between HDMI and CRT sound+image issues.:

So going back to HDMI I'd have to remove/comment audio_pwm_mode=0

You can quickly toggle the option from a script or the console by these commands:

# make a backup of config.txt
cp /boot/config.txt /boot/config.txt.backup
# switch to "1"
sed -i -e 's/audio_pwm_mode=0/audio_pwm_mode=1/g' /boot/config.txt
# switch to "0"
sed -i -e 's/audio_pwm_mode=1/audio_pwm_mode=0/g' /boot/config.txt

The lines beginning with # are comments and can be omitted. Mind the single quotation marks, they're important!

You could save them in convenient executable scripts in a (new) directory called "bin" in your home directory:

cd /home/pi  # make sure we are at home
mkdir bin    # create the directory "bin"
echo "sed -i -e 's/audio_pwm_mode=0/audio_pwm_mode=1/g' /boot/config.txt" > bin/pwm1  # write the first sed command to bin/pwm1
echo "sed -i -e 's/audio_pwm_mode=1/audio_pwm_mode=0/g' /boot/config.txt" > bin/pwm0  # write the second sed command to bin/pwm0
chmod u+x bin/pwm1  # make pwn1 executable
chmod u+x bin/pwm0  # make pwn0 executable

Since $HOME/bin is part of the console's search paths for commands and scripts, you can now just execute pwm1 or pwm0from any directory to toggle the option audio_pwm_mode between 1 an 0.

Besides that matter, do you know that you can enable an experimental audio driver with audio_pwm_mode=2? It fixed an annoying static noice on my Pi.