linux - linux服务器上的modprobe snd-dummy，ffmpeg -f alsa正在记录噪音
问题描述
有人说参数fake_buffer可以去除噪音，但是我试了一下还是有噪音
modprobe snd-dummy fake_buffer=0
#modprobe snd-dummy fake_buffer=0
# lsmod |grep snd
snd_dummy 24576 0
snd_pcm_oss 61440 0
snd_mixer_oss 28672 1 snd_pcm_oss
snd_pcm 118784 2 snd_pcm_oss,snd_dummy
snd_timer 36864 1 snd_pcm
snd 94208 5 snd_timer,snd_pcm_oss,snd_pcm,snd_dummy,snd_mixer_oss
soundcore 16384 1 snd
# modinfo snd_dummy
filename: /lib/modules/4.14.129-bbrplus/kernel/sound/drivers/snd-dummy.ko
license: GPL
description: Dummy soundcard (/dev/null)
author: Jaroslav Kysela <perex@perex.cz>
depends: snd-pcm,snd
retpoline: Y
intree: Y
name: snd_dummy
vermagic: 4.14.129-bbrplus SMP mod_unload modversions
parm: index:Index value for dummy soundcard. (array of int)
parm: id:ID string for dummy soundcard. (array of charp)
parm: enable:Enable this dummy soundcard. (array of bool)
parm: model:Soundcard model. (array of charp)
parm: pcm_devs:PCM devices # (0-4) for dummy driver. (array of int)
parm: pcm_substreams:PCM substreams # (1-128) for dummy driver. (array of int)
parm: fake_buffer:Fake buffer allocations. (bool)
parm: hrtimer:Use hrtimer as the timer source. (bool)
#aplay -L
null
Discard all samples (playback) or generate zero samples (capture)
pulse
PulseAudio Sound Server
dummy
default:CARD=Dummy
Dummy, Dummy PCM
Default Audio Device
sysdefault:CARD=Dummy
Dummy, Dummy PCM
Default Audio Device
dmix:CARD=Dummy,DEV=0
Dummy, Dummy PCM
Direct sample mixing device
dsnoop:CARD=Dummy,DEV=0
Dummy, Dummy PCM
Direct sample snooping device
hw:CARD=Dummy,DEV=0
Dummy, Dummy PCM
Direct hardware device without any conversions
plughw:CARD=Dummy,DEV=0
Dummy, Dummy PCM
Hardware device with all software conversions
# ffmpeg -f alsa -i hw:0 -t 5 /dev/shm/out.mp3 -y
ffmpeg version 3.4.8-0ubuntu0.2 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
configuration: --prefix=/usr --extra-version=0ubuntu0.2 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
libavutil 55. 78.100 / 55. 78.100
libavcodec 57.107.100 / 57.107.100
libavformat 57. 83.100 / 57. 83.100
libavdevice 57. 10.100 / 57. 10.100
libavfilter 6.107.100 / 6.107.100
libavresample 3. 7. 0 / 3. 7. 0
libswscale 4. 8.100 / 4. 8.100
libswresample 2. 9.100 / 2. 9.100
libpostproc 54. 7.100 / 54. 7.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, alsa, from 'hw:0':
Duration: N/A, start: 1616225206.353453, bitrate: 1536 kb/s
Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s16le (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to '/dev/shm/out.mp3':
Metadata:
TSSE : Lavf57.83.100
Stream #0:0: Audio: mp3 (libmp3lame), 48000 Hz, stereo, s16p
Metadata:
encoder : Lavc57.107.100 libmp3lame
size= 79kB time=00:00:05.01 bitrate= 129.0kbits/s speed= 1x
video:0kB audio:79kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.293899%
我使用alsamixer将所有音量设置为0，仍然有噪音我在谷歌搜索了很长时间，没有发现其他人有这个问题，我哪里做错了