[alsa-devel] Missing surround channels with Nvidia HDMI & snd-hda-intel driver

[VDR User]

Hi. I just noticed that I'm missing some surround channels and I think
it may be a bug in the alsa drivers because my current setup used to
work just fine. I'm running Debian Testing, stable kernel 4.13.12,
alsa-utils 1.1.3-1. My ~/.asoundrc is:

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

I am not setting anything on my kernel load line:

        echo    'Loading Linux 4.13.12-amd ...'
        linux   /vmlinuz-4.13.12-amd
root=UUID=6df5733d-b089-450c-9ec6-661dd013c7c0 ro
        echo    'Loading initial ramdisk ...'
        initrd  /initrd.img-4.13.12-amd

The driver being used is snd-hda-intel with an Nvidia GT520 video
card. And lastly I do not have Pulse or a desktop environment. This is
a minimal HTPC setup that runs only an xserver to provide video
output, with audio/video being sent to my surround receiver via HDMI.

The first thing I noticed was mpv-player was downmixing 5.1 to 3.1 and
giving the following log message:

[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
[af] Audio filter chain:
[af]   [in] 44100Hz 5.1 6ch floatp
[af]   [lavrresample] 44100Hz fl-fr-fc-lfe-na-na (3.1) 6ch s32 [a]
[af]   [out] 44100Hz fl-fr-fc-lfe-na-na (3.1) 6ch s32
[af]   [ao] 44100Hz fl-fr-fc-lfe-na-na (3.1) 6ch s32

That makes it look like Rear Left/Right channels are absent. I think
ran speaker-test. 4 and 5 show as "Unknown" but correctly audibly
announced as "front center" and "subwoofer" respectively:

~$ 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

Additional information that may be of use:

~$ 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: 0/1
  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

02:00.0 VGA compatible controller: NVIDIA Corporation GF119 [GeForce
GT 520] (rev a1) (prog-if 00 [VGA controller])
        Subsystem: eVga.com. Corp. GF119 [GeForce GT 520]
        Flags: bus master, fast devsel, latency 0, IRQ 25
        Memory at fd000000 (32-bit, non-prefetchable) [size=16M]
        Memory at f0000000 (64-bit, prefetchable) [size=128M]
        Memory at fa000000 (64-bit, prefetchable) [size=32M]
        I/O ports at ec00 [size=128]
        [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
        Capabilities: <access denied>
        Kernel driver in use: nvidia
        Kernel modules: nvidia

02:00.1 Audio device: NVIDIA Corporation GF119 HDMI Audio Controller (rev a1)
        Subsystem: eVga.com. Corp. GF119 HDMI Audio Controller
        Flags: bus master, fast devsel, latency 0, IRQ 17
        Memory at fea7c000 (32-bit, non-prefetchable) [size=16K]
        Capabilities: <access denied>
        Kernel driver in use: snd_hda_intel
        Kernel modules: snd_hda_intel