Triode wrote: 
> Can't comment in detail on the pi hdmi output as I've not used it. 
> However you can see what squeezelite is opening the devices as, if you
> start it with "-d output=sdebug"
> 
> You won't want to run like this as it produces lots of information, but
> at the top of it it will show how the different alsa layers are
> configured and what sample rates they are using for the output.

OK - think I may understand it a little ....

The test file I have is S24_LE.  When I try and aplay it with with
asound.conf, which calls a converter by the look of it, it resamples it
to 48khz.  If I run sdebug, the top of the log file says ...

[19:34:45.293901] output_init:932 init output
[19:34:45.295553] output_init:935 outputbuf size: 3528000
[19:34:45.383241] output_init:954 output: default maxrate: 192000
[19:34:45.384078] output_thread:326 open output device: default
[19:34:45.394895] alsa_open:221 opened device default using format:
S32_LE sample rate: 44100
[19:34:45.396395] alsa_open:265 buffer time: 23219 period count: 4
buffer size: 1024 period size: 256
Plug PCM: Linear conversion PCM (S16_LE)
Its setup is:
stream       : PLAYBACK
access       : MMAP_INTERLEAVED
format       : S32_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 32
buffer_size  : 1024
period_size  : 256
period_time  : 5804
tstamp_mode  : NONE
period_step  : 1
avail_min    : 256
period_event : 0
start_threshold  : 1
stop_threshold   : 1024
silence_threshold: 0
silence_size : 0
boundary     : 1073741824
Slave: Mmap emulation PCM
Its setup is:
stream       : PLAYBACK
access       : MMAP_INTERLEAVED
format       : S16_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 16
buffer_size  : 1024
period_size  : 256
period_time  : 5804
tstamp_mode  : NONE
period_step  : 1
avail_min    : 256
period_event : 0
start_threshold  : 1
stop_threshold   : 1024
silence_threshold: 0
silence_size : 0
boundary     : 1073741824
Slave: Hardware PCM card 0 'bcm2835 ALSA' device 0 subdevice 0
Its setup is:
stream       : PLAYBACK
access       : RW_INTERLEAVED
format       : S16_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 16
buffer_size  : 1024
period_size  : 256
period_time  : 5804
tstamp_mode  : NONE
period_step  : 1
avail_min    : 256
period_event : 0
start_threshold  : 1073741824
stop_threshold   : 1024
silence_threshold: 0
silence_size : 0
boundary     : 1073741824
appl_ptr     : 0
hw_ptr       : 0


So, I was very confused - it supports upto 192K!  So, I tried removing
the asound.conf completely, did an aplay -v and got ....

pi@raspberrypi ~ $ aplay -v 96.wav
Playing WAVE '96.wav' : Signed 24 bit Little Endian in 3bytes, Rate
96000 Hz, S
ereo
aplay: set_params:1081: Sample format non available
Available formats:
- U8
- S16_LE
- S16_BE
- S32_LE
- S32_BE
- FLOAT_LE
- FLOAT_BE
- MU_LAW
- A_LAW

Ah!  No S24_LE.  So, connecting to my AV proc over HDMI seems to not
list S24 as available formats if I'm reading that right - hence causing
the resampling, which is defaulting to 48K.  No idea why it would
support S16 and S32 but not S24.  I wonder if there's some way to tell
ALSA, no, it really does support S24 (just to give it a try).  All my HD
stuff seems to be 24bit, so could be a bit of a problem....


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