Description of problem: Can no longer capture sound from any sound device that uses snd-usb-audio module. (E.g. a USB webcam) Version-Release number of selected component (if applicable): ALSA 1.0.15 How reproducible: Very. I have tried two different webcam devices, and one creates a 44 byte file only while the other creates a big file of silence. Steps to Reproduce: 1. Define webcam in .asoundrc file as ctl.webcam { type hw card 1 } pcm.webcam { type plug slave { pcm "hw:1,0" } } 3. Set mixer setting via "alsamixer -c 1" 4. arecord -D webcam -t wav -f cd -d 5 > testing.wav 5. aplay testing.wav Actual results: One webcam creates 5 seconds of silence, while the other creates a 44 byte file and then hangs. Expected results: A .wav file of whatever noise is picked up by the microphone. This certainly used to work. Additional info:
Created attachment 269271 [details] The only scrap of a WAV file that arecord could generate.
This is what "aplay -L" says on my machine. I am wondering why both webcams show up in this list, because these devices are capture-only: $ aplay -L default:CARD=Audigy2 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Default Audio Device front:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Front speakers rear:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Rear speakers center_lfe:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Center and Subwoofer speakers side:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Side speakers surround40:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 4.0 Surround output to Front and Rear speakers surround41:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 4.1 Surround output to Front, Rear and Subwoofer speakers surround50:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 5.0 Surround output to Front, Center and Rear speakers surround51:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 5.1 Surround output to Front, Center, Rear and Subwoofer speakers surround71:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 7.1 Surround output to Front, Center, Side, Rear and Woofer speakers iec958:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback IEC958 (S/PDIF) Digital Audio Output null Discard all samples (playback) or generate zero samples (capture) default:CARD=WebCam USB Device 0x46d:0x8b4, USB Audio Default Audio Device front:CARD=WebCam,DEV=0 USB Device 0x46d:0x8b4, USB Audio Front speakers surround40:CARD=WebCam,DEV=0 USB Device 0x46d:0x8b4, USB Audio 4.0 Surround output to Front and Rear speakers surround41:CARD=WebCam,DEV=0 USB Device 0x46d:0x8b4, USB Audio 4.1 Surround output to Front, Rear and Subwoofer speakers surround50:CARD=WebCam,DEV=0 USB Device 0x46d:0x8b4, USB Audio 5.0 Surround output to Front, Center and Rear speakers surround51:CARD=WebCam,DEV=0 USB Device 0x46d:0x8b4, USB Audio 5.1 Surround output to Front, Center, Rear and Subwoofer speakers surround71:CARD=WebCam,DEV=0 USB Device 0x46d:0x8b4, USB Audio 7.1 Surround output to Front, Center, Side, Rear and Woofer speakers iec958:CARD=WebCam,DEV=0 USB Device 0x46d:0x8b4, USB Audio IEC958 (S/PDIF) Digital Audio Output default:CARD=WebCam2 USB Device 0x46d:0x8dd, USB Audio Default Audio Device front:CARD=WebCam2,DEV=0 USB Device 0x46d:0x8dd, USB Audio Front speakers surround40:CARD=WebCam2,DEV=0 USB Device 0x46d:0x8dd, USB Audio 4.0 Surround output to Front and Rear speakers surround41:CARD=WebCam2,DEV=0 USB Device 0x46d:0x8dd, USB Audio 4.1 Surround output to Front, Rear and Subwoofer speakers surround50:CARD=WebCam2,DEV=0 USB Device 0x46d:0x8dd, USB Audio 5.0 Surround output to Front, Center and Rear speakers surround51:CARD=WebCam2,DEV=0 USB Device 0x46d:0x8dd, USB Audio 5.1 Surround output to Front, Center, Rear and Subwoofer speakers surround71:CARD=WebCam2,DEV=0 USB Device 0x46d:0x8dd, USB Audio 7.1 Surround output to Front, Center, Side, Rear and Woofer speakers iec958:CARD=WebCam2,DEV=0 USB Device 0x46d:0x8dd, USB Audio IEC958 (S/PDIF) Digital Audio Output Here is what "arecord -L" says on the same machine: $ arecord -L default:CARD=Audigy2 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Default Audio Device front:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Front speakers rear:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Rear speakers center_lfe:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Center and Subwoofer speakers side:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback Side speakers surround40:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 4.0 Surround output to Front and Rear speakers surround41:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 4.1 Surround output to Front, Rear and Subwoofer speakers surround50:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 5.0 Surround output to Front, Center and Rear speakers surround51:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 5.1 Surround output to Front, Center, Rear and Subwoofer speakers surround71:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback 7.1 Surround output to Front, Center, Side, Rear and Woofer speakers iec958:CARD=Audigy2,DEV=0 Audigy 2 ZS [SB0353], ADC Capture/Standard PCM Playback IEC958 (S/PDIF) Digital Audio Output null Discard all samples (playback) or generate zero samples (capture)
This is now looking like "user error", as I have now managed to capture sound with all but one of my webcams. The problem so far has been not setting an unexpected mixer setting (found by examining /etc/alsa/asound.state). Previously I was just setting the capture level via alsamixer, but apparently there's an ON/OFF setting too. The remaining webcam is behaving as if some other application has grabbed the capture device so that arecord is left hanging uselessly until it becomes free again. To date, I have not worked out which other application it might be.