Why does ALSA upsample to 48kHz when playing a 44.1kHz wav with a device
capable of 44.1kHz? How do I understand what is happening? Where is the
configuration (OpenSuse 12.2 with no asoundrc or similar)? Where is the
documentation?
Evidence below, Andrew
> cat /proc/asound/D1/stream0
2010 REV 1.7 Audioengine D1 at usb-0000:00:12.2-3.2.4.1,
full : USB Audio
Playback:
Status: Running
Interface = 1
Altset = 2
URBs = 3 [ 8 8 8 ]
Packet Size = 600
Momentary freq = 48000 Hz (0x30.0000)
Feedback Format = 10.14
Interface 1
Altset 1
Format: S24_3LE
Channels: 2
Endpoint: 1 OUT (ASYNC)
Rates: 96000, 88200, 48000, 44100, 32000
Interface 1
Altset 2
Format: S16_LE
Channels: 2
Endpoint: 1 OUT (ASYNC)
Rates: 96000, 88200, 48000, 44100, 32000
> Playing WAVE '/crypto/music/test.wav' : Signed 16 bit Little Endian, Rate
> 44100 Hz, Mono
Plug PCM: Rate conversion PCM (48000, sformat=S16_LE)
Converter: libspeex (builtin)
Protocol version: 10002
Its setup is:
stream : PLAYBACK
access : RW_INTERLEAVED
format : S16_LE
subformat : STD
channels : 1
rate : 44100
exact rate : 44100 (44100/1)
msbits : 16
buffer_size : 15052
period_size : 940
period_time : 21333
tstamp_mode : NONE
period_step : 1
avail_min : 940
period_event : 0
start_threshold : 15052
stop_threshold : 15052
silence_threshold: 0
silence_size : 0
boundary : 4236761349448794112
Slave: Route conversion PCM (sformat=S16_LE)
Transformation table:
0 <- 0
1 <- 0
Its setup is:
stream : PLAYBACK
access : MMAP_INTERLEAVED
format : S16_LE
subformat : STD
channels : 1
rate : 48000
exact rate : 48000 (48000/1)
msbits : 16
buffer_size : 16384
period_size : 1024
period_time : 21333
tstamp_mode : NONE
period_step : 1
avail_min : 1024
period_event : 0
start_threshold : 16384
stop_threshold : 16384
silence_threshold: 0
silence_size : 0
boundary : 4611686018427387904
Slave: Direct Stream Mixing PCM
Its setup is:
stream : PLAYBACK
access : MMAP_INTERLEAVED
format : S16_LE
subformat : STD
channels : 2
rate : 48000
exact rate : 48000 (48000/1)
msbits : 16
buffer_size : 16384
period_size : 1024
period_time : 21333
tstamp_mode : NONE
period_step : 1
avail_min : 1024
period_event : 0
start_threshold : 16384
stop_threshold : 16384
silence_threshold: 0
silence_size : 0
boundary : 4611686018427387904
Hardware PCM card 2 'Audioengine D1' device 0 subdevice 0
Its setup is:
stream : PLAYBACK
access : MMAP_INTERLEAVED
format : S16_LE
subformat : STD
channels : 2
rate : 48000
exact rate : 48000 (48000/1)
msbits : 16
buffer_size : 16384
period_size : 1024
period_time : 21333
tstamp_mode : ENABLE
period_step : 1
avail_min : 1024
period_event : 0
start_threshold : 1
stop_threshold : 4611686018427387904
silence_threshold: 0
silence_size : 4611686018427387904
boundary : 4611686018427387904
appl_ptr : 0
hw_ptr : 0
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