Some surround channels missing..

Hi. I just noticed that 5.1 surround was not playing correctly. I’m not sure when this started to happen but it used to work fine. I’ve posted to the alsa mailing list thinking it may be a snd-hda-intel sound driver problem but it was suggested this could be an nvidia driver issue as well. Are there currently any known problems with surround sound? Here’s my info:

32bit Debian Testing, stable kernel 4.13.12, Nvidia GT520 video card connected to surround receiver via HDMI, nvidia driver 375.82.

When I try to play something in mpv with surround, I see this:
[ao/alsa] trying to set ALSA channel map: FL FR FC LFE RL RR
[ao/alsa] channel map reported by ALSA: FL FR FC LFE UNKNOWN UNKNOWN
[ao/alsa] which we understand as: fl-fr-fc-lfe-na-na
[ao/alsa] using the ALSA channel map.
[ao/alsa] hw pausing supported: yes
[ao/alsa] buffersize: 2720 samples
[ao/alsa] period size: 160 samples
[ao/alsa] device buffer: 2720 samples.
[ao/alsa] using soft-buffer of 8820 samples.
[cplayer] AO: [alsa] 44100Hz fl-fr-fc-lfe-na-na (3.1) 6ch s32
[cplayer] AO: Description: ALSA audio output
[af] Adding filter lavrresample
[lavrresample] Remix: 5.1 -> 3.1

The UNKNOWN’s are the problem it seems. When I do speaker-test I get:
~$ speaker-test -c 6 -t wav

speaker-test 1.1.3

Playback device is default
Stream parameters are 48000Hz, S16_LE, 6 channels
WAV file(s)
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 64 to 5440
Period size range from 32 to 2720
Using max buffer size 5440
Periods = 4
was set period_size = 1088
was set buffer_size = 5440
0 - Front Left
1 - Front Right
3 - Rear Right
2 - Rear Left
4 - Unknown
5 - Unknown
Time per period = 8.525927

4 and 5 show as unknown but the audio correctly says “front center” for 4, and “subwoofer” for 5. Here’s some other information that may be useful:

~$ cat .asoundrc
pcm.!default “hdmi:NVidia,1”

~$ aplay -L
null
Discard all samples (playback) or generate zero samples (capture)
hdmi:CARD=NVidia,DEV=0
HDA NVidia, HDMI 0
HDMI Audio Output
hdmi:CARD=NVidia,DEV=1
HDA NVidia, HDMI 1
HDMI Audio Output
dmix:CARD=NVidia,DEV=3
HDA NVidia, HDMI 0
Direct sample mixing device
dmix:CARD=NVidia,DEV=7
HDA NVidia, HDMI 1
Direct sample mixing device
dsnoop:CARD=NVidia,DEV=3
HDA NVidia, HDMI 0
Direct sample snooping device
dsnoop:CARD=NVidia,DEV=7
HDA NVidia, HDMI 1
Direct sample snooping device
hw:CARD=NVidia,DEV=3
HDA NVidia, HDMI 0
Direct hardware device without any conversions
hw:CARD=NVidia,DEV=7
HDA NVidia, HDMI 1
Direct hardware device without any conversions
plughw:CARD=NVidia,DEV=3
HDA NVidia, HDMI 0
Hardware device with all software conversions
plughw:CARD=NVidia,DEV=7
HDA NVidia, HDMI 1
Hardware device with all software conversions

~ aplay -l **** List of PLAYBACK Hardware Devices **** card 1: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 card 1: NVidia [HDA NVidia], device 7: HDMI 1 [HDMI 1] Subdevices: 1/1 Subdevice #0: subdevice #0 ~

~$ cat /proc/asound/card1/eld#0.1
monitor_present 1
eld_valid 1
monitor_name SONY AVAMP

connection_type HDMI
eld_version [0x2] CEA-861D or below
edid_version [0x3] CEA-861-B, C or D
manufacture_id 0xd94d
product_id 0xf02
port_id 0x200
support_hdcp 0
support_ai 0
audio_sync_delay 0
speakers [0x5f] FL/FR LFE FC RL/RR RC RLC/RRC
sad_count 12
sad0_coding_type [0xc] MLP (Dolby TrueHD)
sad0_channels 2
sad0_rates [0x1ec0] 44100 48000 88200 96000 176400 192000
sad1_coding_type [0xc] MLP (Dolby TrueHD)
sad1_channels 6
sad1_rates [0x1ec0] 44100 48000 88200 96000 176400 192000
sad2_coding_type [0xc] MLP (Dolby TrueHD)
sad2_channels 8
sad2_rates [0x6c0] 44100 48000 88200 96000
sad3_coding_type [0xb] DTS-HD
sad3_channels 2
sad3_rates [0x1ec0] 44100 48000 88200 96000 176400 192000
sad4_coding_type [0xb] DTS-HD
sad4_channels 6
sad4_rates [0x1ec0] 44100 48000 88200 96000 176400 192000
sad5_coding_type [0xb] DTS-HD
sad5_channels 8
sad5_rates [0x6c0] 44100 48000 88200 96000
sad6_coding_type [0x1] LPCM
sad6_channels 2
sad6_rates [0x1ee0] 32000 44100 48000 88200 96000 176400 192000
sad6_bits [0xe0000] 16 20 24
sad7_coding_type [0x1] LPCM
sad7_channels 6
sad7_rates [0x1ee0] 32000 44100 48000 88200 96000 176400 192000
sad7_bits [0xe0000] 16 20 24
sad8_coding_type [0x1] LPCM
sad8_channels 8
sad8_rates [0x1ee0] 32000 44100 48000 88200 96000 176400 192000
sad8_bits [0xe0000] 16 20 24
sad9_coding_type [0x2] AC-3
sad9_channels 6
sad9_rates [0xe0] 32000 44100 48000
sad9_max_bitrate 680000
sad10_coding_type [0x7] DTS
sad10_channels 6
sad10_rates [0x6e0] 32000 44100 48000 88200 96000
sad10_max_bitrate 1536000
sad11_coding_type [0xa] E-AC-3/DD+ (Dolby Digital Plus)
sad11_channels 8
sad11_rates [0xc0] 44100 48000