raspberry only play mono sound

Question

I installed raspbian using noobs on a fresh SD card.

I have XBian with XBMC in another SD and it works so HW is Ok.

The problem is that I cannot play stereo, thus I cannot play through HDMI, and I cannot play from ZynAddSubFX that is a midi sampler and my final target for this project.

This is the result from amixer:

Simple mixer control 'PCM',0
Capabilities: pvolume pvolume-joined pswitch pswitch-joined penum
Playback channels: Mono
Limits: Playback -10239 - 400
Mono: Playback -1900 [78%] [-19.00dB] [on]

the Mono playback is weird for me and the Limites of the playback are also suspicious. If I install pulseaudio then amixer takes A LOT OF TIME to respond BUT this is the result:

amixer
Simple mixer control 'Master',0
  Capabilities: pvolume pswitch pswitch-joined penum
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 65536
  Mono:
  Front Left: Playback 27111 [41%] [on]
  Front Right: Playback 27111 [41%] [on]
Simple mixer control 'Capture',0
  Capabilities: cvolume cswitch cswitch-joined penum
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 65536
  Front Left: Capture 65536 [100%] [on]
  Front Right: Capture 65536 [100%] [on]

Much more convenient and expected.

The problem is that I DON'T want to use pulseaudio and, actually, I think ZynAddSubFX is not compatible with pulseaudio.

For sure I've googled around a lot but there is no clear solution. I found out the trick for forcing analog output (amixer cset numId=3 1) it works in terms that I do hear something but the main problem is there .. only mono.

this is the output for lsmod:

lsmod
Module                  Size  Used by
snd_bcm2835            16165  0
snd_soc_bcm2708_i2s     5474  0
regmap_mmio             2806  1 snd_soc_bcm2708_i2s
snd_soc_core          131268  1 snd_soc_bcm2708_i2s
regmap_spi              1897  1 snd_soc_core
snd_pcm                81593  2 snd_bcm2835,snd_soc_core
snd_page_alloc          5156  1 snd_pcm
regmap_i2c              1645  1 snd_soc_core
snd_compress            8076  1 snd_soc_core
snd_seq                53769  0
snd_timer              20133  2 snd_pcm,snd_seq
snd_seq_device          6473  1 snd_seq
leds_gpio               2059  0
led_class               3688  1 leds_gpio
snd                    61291  7 
snd_bcm2835,snd_soc_core,snd_timer,snd_pcm,snd_seq,snd_seq_device,snd_compress

Any clue ?? Any other output that might be interesting ??

Answer 1

I finally "solved" by buying a 1.34€ USB sound card. I dont really thing that this count as a solution but .. I needed the mic line anyhow

Answer 2

I'm using Debian 4.4.6-1+rpi14 (2016-05-05) and have a very similar problem. The sound is mono only when using ALSA. The the sound is not continuous and the quality is poor. If I use omxplayer the output is stereo and the sound quality is good. I've found if I use mplayer -ao alsa:device=hw=0,0 then the sound quality is as good as using omxplayer and it is stereo! Somehow ALSA is not functioning normally if the default device hw:0.0 is not given as an parameter. So the solution for pulseaudio is to add the the device=hw:0,0 option.

pactl load-module module-alsa-sink device="hw:0,0"
pactl set-default-sink alsa_output.hw_0_0

Now pulseaudio shows stereo output and the sound quality is as good as omxplayer.

Answer 3

Late answer but I can still relevant at this date: I faced the same problem (mono sound through hdmi output) with the ubuntu distro for raspberry pi, but everything works fine when using the raspbian distro from raspberry web site.