WM8960 soundcard on RPi Zero2 seems stuck at 48000Hz, how to change to 44100Hz

Greetings LQ. I am working on a Raspberry Pi Zero 2 and recently attached a Waveshare WM8960 Hi-Fi soundcard. The OS is RetroPie and the Waveshare driver installation did an apt upgrade so all of the packages are up-to-date and the kernel is 5.10.81+ (IIRC).

My plan for this Pi project is a dedicated MAME system, specifically mame2000. The monitor will be either VGA or DVI, and either way it will need an alternate soundcard, whether USB or GPIO. The libretro mame2000 core is okay but mame4all is preferred due to performance and supporting hiscores and cheat files.

Before adding the Waveshare card both the lr-mame2000 and mame4all cores played the games fine over HDMI audio. Now with the soundcard attached the lr-mame2000 works fine but mame4all fails to launch. At first the log file had an ALSA error of

Unable to set hw params for PLAYBACK: Invalid argument

I spent much of the past few days Googling the error and studying the .asoundrc file to find an answer. As far as I can tell, mame4all specifically wants an ALSA device named PCM, and I solved that by creating an alias in ~/.asoundrc. Now the error is

Rate doesn't match (requested 44100Hz, get 48000Hz)

I've seen some posts in other forums about this error with USB audio adapters and was solved by adding rate 44100 and format S16_LE somewhere in .asoundrc. I have been trying for several hours now, following the asoundrc guide at alsa-project.org, to get such a line in .asoundrc to work. I even tried editing the 10-xxxx files in /etc/alsa/conf.d to change the default rate from 48000 to 44100. Nothing worked.

After a while I started trying to use aplay with a .wav file from /usr/share/sounds/alsa to test if it is capable of 44100. I tested with several of the names in my .asoundrc with -r 44100 and every time the playback status shows 48000. Finally, I looked in the wm8960.c file of the source code and there is one section about alc_rates

} alc_rates[] = {
	{ 48000, 0 },
	{ 44100, 0 },
	{ 32000, 1 },
	{ 22050, 2 },
	{ 24000, 2 },
	{ 16000, 3 },
	{ 11025, 4 },
	{ 12000, 4 },
	{  8000, 5 },
};

Then further down is this

#define WM8960_RATES SNDRV_PCM_RATE_8000_48000

I may be wrong but it looks like it is capable, but how can I get it to work?

The source files are located at https://github.com/waveshare/WM8960-Audio-HAT
Also, the ~/.asoundrc file I am using is an unmodified copy of the asound.conf from the above link. At this point I have removed all of my failed attempts, and the only addition I have in place is the following alias which originally gives the "Rate doesn't match" error

pcm_slave.pcm { pcm "dmixed" }

Thank in advance

If you need 44100 for some reason (?) you may be able to resample at that speed by setting that up in /etc/asound.conf. I had the reverse done to get over a hdmi quality issue on drivers at the time.

Thanks for the idea. I'll give that a try as soon as I get a chance. I tried a lot of things in ~/.asoundrc, but not in /etc/asound.conf. I'm pretty sure mame4all specifically wants 44,100Hz just like it specifically wants a device named pcm.

pcm is one of the alsa input channels. Frankly I don't think you setup is going to change the results. I'd be looking at the config.txt settings. If yopu're usingh u-boot, put the line calling u-boot.bin at the very end of config.txt, becausew the firmware doesn't seem to act on the rest of config.txt IME. It means all your 'dtparams' settings get acted on.

I had a chance to check the /etc/asound.conf, and it is a symlink to the same asound config file provided by the soundcard driver.

I did find the mame.cfg file used by mame4all, and includes the default samplerate set to 44100. I tried changing it to 48000, but still get the same error.

Then I opened a terminal and navigated to /opt/retropie/emulators/mame4all to try it without the frontend. I run the command

./mame 1942b

and get the same error in the command output, instead of the /dev/shm/runcommand.log file. Then I found the mame option to specify the rate and tried it

./mame 1942b -samplerate 48000

and still get the same error.