Am Freitag, 26. September 2014, 14:21:28 schrieb Sven Moeller: > Hello List, > > recently I've bought this Mic. The AKG Perception 120 USB has a 24 bit A/D > converter with 128x oversampling. But alsa recognizes just 16bit. When I do > record "just silence" I get a white noise. In the alsamixer I set the > volume of the Mic to ~43%. On the vu-meter arecord shows nothing. But > Audacity shows amplitudes on the vu-meter. I was trying to force the 24bit > support by unloading the usb-snd-audio module, unplugging the mic and > loading the module by hand like this: > > modprobe usb-snd-audio device_setup=0x09 > > After plugging in the mic nothing has changed. arecord --dump-hw-params -D > hw:USB reports just the same sample format 16bit little endian instead of a > 24bit format. > > Is this "just" an issue with the initalization of the microphone? Or is it > not supported by the driver completely? > > I did test this on my PC (ARCH-Linux, AMD Opteron 1356 QuadCore, 8GB RAM, > Foxcon DigitialLife Mainboard). I did the test on my WeTab (Manjaro with > Netbook Optimized Kernel 3.12) also with the same result. > > > Any suggestions how to get rid of this static white noise? > > thx & kind regards > > Sven
So, here's the technical point of view: 1. sudo modprobe snd-usb-audio index=1 device_setup=0x09 2. microphone pluged in. 3. [ 271.572941] usbcore: registered new interface driver snd-usb-audio [ 293.114507] usb 5-2: new full-speed USB device number 2 using ohci-pci [ 293.294760] usb 5-2: current rate 0 is different from the runtime rate 48000 [ 293.300760] usb 5-2: current rate 0 is different from the runtime rate 48000 [ 770.206791] usb 5-2: current rate 8000 is different from the runtime rate 48000 4. **** List of CAPTURE Hardware Devices **** card 0: SB [HDA ATI SB], device 0: ALC1200 Analog [ALC1200 Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: SB [HDA ATI SB], device 2: ALC1200 Alt Analog [ALC1200 Alt Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 1: USB [AKG Perception 120 USB], device 0: USB Audio [USB Audio] Subdevices: 1/1 Subdevice #0: subdevice #0 5. arecord --dump-hw-params -D hw:USB Recording WAVE 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono HW Params of device "hw:USB": -------------------- ACCESS: MMAP_INTERLEAVED RW_INTERLEAVED FORMAT: S8 S16_LE SUBFORMAT: STD SAMPLE_BITS: [8 16] FRAME_BITS: [8 32] CHANNELS: [1 2] RATE: [6400 48000] PERIOD_TIME: [1000 81920000] PERIOD_SIZE: [16 524288] PERIOD_BYTES: [64 524288] PERIODS: [2 1024] BUFFER_TIME: (666 163840000] BUFFER_SIZE: [32 1048576] BUFFER_BYTES: [64 1048576] TICK_TIME: ALL -------------------- arecord: set_params:1233: Sample format non available Available formats: - S8 - S16_LE Here at "Available formats" I do expect kinda 24bit format. But nothing. If I execute arecord --dump-hw-params -D plughw:USB I get this output: Recording WAVE 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono HW Params of device "plughw:USB": -------------------- ACCESS: MMAP_INTERLEAVED MMAP_NONINTERLEAVED MMAP_COMPLEX RW_INTERLEAVED RW_NONINTERLEAVED FORMAT: S8 U8 S16_LE S16_BE U16_LE U16_BE S24_LE S24_BE U24_LE U24_BE S32_LE S32_BE U32_LE U32_BE FLOAT_LE FLOAT_BE FLOAT64_LE FLOAT64_BE MU_LAW A_LAW IMA_ADPCM S24_3LE S24_3BE U24_3LE U24_3BE S20_3LE S20_3BE U20_3LE U20_3BE S18_3LE S18_3BE U18_3LE U18_3BE SUBFORMAT: STD SAMPLE_BITS: [4 64] FRAME_BITS: [4 640000] CHANNELS: [1 10000] RATE: [4000 4294967295] PERIOD_TIME: [1000 81920000] PERIOD_SIZE: [4 4294967295] PERIOD_BYTES: [2 4294967295] PERIODS: (0 1073741824) BUFFER_TIME: [1 4294967295] BUFFER_SIZE: [2 4294967294] BUFFER_BYTES: [1 4294967295] TICK_TIME: ALL -------------------- RIFF$�WAVEfmt @data���������~��~���~���������~���~~���~�~��^CAborted by signal Interrupt... arecord: pcm_read:2031: read error: Interrupted system call hit <ctrl>+<c> Huh? What's the difference bitween -D hw:usb and -D plughw:USB in this case? Is the line starting with @data captured data by the mic? Is arecord not able to determine supported formats? Maybe this is something for the Devs? Sven
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