ALSALOOP(1)

✨ ALSALOOP(1) 💖 — General Commands Manual ✨

🎀 NAME

Okay so bestie, the manual name here is alsaloop — it's a command-line PCM loopback. 🦋 It's giving "pipe audio from one place to another" energy 💅

💜 SYNOPSIS

alsaloop [-option] [cmd]

🌸 DESCRIPTION

Okay so alsaloop lets you create a PCM loopback between a PCM capture device and a PCM playback device. 🎧 Literally the audio-routing queen 👑

It's also highkey iconic because it supports multiple soundcards 🔥, adaptive clock synchronization ⭐, and adaptive rate resampling using the samplerate library (if it's available on your system 🫶). And ooh, mixer controls can be redirected from one card to another, like Master and PCM 💅✨

🦋 OPTIONS

• -h, --help — Prints the help information. Bestie, this is your lifeline 🆘💖
• -g <file>, --config=<file> — Use a given configuration file 📄. The syntax is super simple: each line holds the command line options for one job 🎀. A # marks a comment, and the rest of that line gets ignored. Here's an example 👇

# First line - comment, second line - first job
-C hw:1,0 -P hw:0,0 -t 50000 -T 1
# Third line - comment, fourth line - second job
-C hw:1,1 -P hw:0,1 -t 40000 -T 2

• -d, --daemonize — Daemonize the main process and use syslog for messages 🧚 Main character energy.
• -P <device>, --pdevice=<device> — Use the given playback device 🔊
• -C <device>, --cdevice=<device> — Use the given capture device 🎙️
• -X <device>, --pctl=<device> — Use the given CTL device for playback 🎚️
• -Y <device>, --cctl=<device> — Use the given CTL device for capture 🎛️
• -x <ctl_ascii_name>, --prateshift=<ctl_ascii_name> — Specify the ctl ascii name for playshift sync mode 🌈 (check out the Examples section, iykyk).
• -l <latency>, --latency=<frames> — Requested latency in frames ⏱️
• -t <usec>, --tlatency=<usec> — Requested latency in usec (that's 1/1000000 of a second) ⏲️ Tiny but mighty.
• -f <format>, --format=<format> — Format specification (usually S16_LE or S32_LE) 💜 Use -h to see every format on the list. The default is S16_LE, obviously the moment 💅
• -c <channels>, --channels=<channels> — Channel count. The default is 2 🫶
• -r <rate>, --rate=<rate> — Rate specification. The default is 48000 (Hz) 🎶
• -n, --resample — Allow rate resampling using alsa-lib 🔁
• -A <converter>, --samplerate=<converter> — Use libsamplerate and pick a converter 🍓. Your options are:
  • 0 or sincbest — best quality 👑
  • 1 or sincmedium — medium quality ✨
  • 2 or sincfastest — lowest quality 💀
  • 3 or zerohold — hold zero samples 🙈
  • 4 or linear — worst quality, linear resampling 😭
  • 5 or auto — let it choose the best method 🧚
• -B <size>, --buffer=<size> — Buffer size in frames 🧺
• -E <size>, --period=<size> — Period size in frames 🌙
• -s <secs>, --seconds=<secs> — How long the loop runs, in seconds ⏳
• -b, --nblock — Non-block mode, which means very early process wakeup. Heads up: it eats more CPU 🙈⚡
• -S <mode>, --sync=<mode> — Sync mode specification for the capture-to-playback stream. Pick your vibe:
  • 0 or none — do not touch the stream 🫠
  • 1 or simple — add or remove samples to keep both streams synchronized 🔄
  • 2 or captshift — use the driver for the capture device (if supported) to compensate the rate shift 🎤
  • 3 or playshift — use the driver for the playback device (if supported) to compensate the rate shift 🔊
  • 4 or samplerate — use the samplerate library to do rate resampling 🌊
  • 5 or auto — automatically selects the best method, checking in this order: captshift, playshift, samplerate, simple 👑
• -T <num>, --thread=<num> — Thread number. -1 means create a unique thread. All jobs with the same thread numbers run within one thread 🧵
• -m <mixid>, --mixer=<midid> — Redirect a mixer control from the playback card to the capture card 🎚️ The format of mixid is SRCID(PLAYBACK)[@DSTID(PLAYBACK)]. Examples:

"name='Master Playback Switch'@name='Another Switch'"
"name='PCM Playback Volume'"

Known attributes you can use:

• name — control ID name
• index — control ID index
• device — control ID device
• subdevice — control ID subdevice
• iface — control ID interface
• numid — control ID numid

• -O <ossmixid>, --ossmixer=<midid> — Redirect a mixer control from the OSS Mixer emulation layer (capture card) to the ALSA layer (capture card) 🎛️ The format of ossmixid is ALSAID[,INDEX]@OSSID. Examples:

"Master@VOLUME"
"PCM,1@ALTPCM"

Known OSS attributes:

VOLUME, BASS, TREBLE, SYNTH, PCM, SPEAKER, LINE, MIC, CD, IMIX, ALTPCM, RECLEV, IGAIN, OGAIN, LINE1, LINE2, LINE3, DIGITAL1, DIGITAL2, DIGITAL3, PHONEIN, PHONEOUT, VIDEO, RADIO, MONITOR

• -v, --verbose — Verbose mode. Use it multiple times to turn up the verbosity 📢
• -U, --xrun — Verbose xrun profiling 🕵️‍♀️
• -W <timeout>, --wake=<timeout> — Set the process wake timeout ⏰

🧁 EXAMPLES

alsaloop -C hw:0,0 -P hw:1,0 -t 50000

alsaloop -C hw:soundcard,0 -P hw:Loopback,0 -t 50000 -S playshift \
-x iface=PCM,name='PCM Rate Shift 100000',device=1

🐛 BUGS

None known. Bestie, that's a clean record 💅✨

👩‍💻 AUTHOR

alsaloop is by Jaroslav Kysela <perex@perex.cz>. This document is by Jaroslav Kysela <perex@perex.cz> too 🫶

Bye bestie, that's the whole page 💖 Source is the 5 Aug 2010 version of ALSALOOP(1), so go loop some audio and slay forever 🦋✨