roc-recv OPTIONS


Receive audio streams from remote senders and write them to an audio device or file.


-h, --help

Print help and exit

-V, --version

Print version and exit

-v, --verbose

Increase verbosity level (may be used multiple times)

-L, --list-supported

list supported schemes and formats

-o, --output=IO_URI

Output file or device URI


Force output file format


Backup file or device URI (if set, used when there are no sessions)


Force backup file format

-s, --source=ENDPOINT_URI

Local source endpoint

-r, --repair=ENDPOINT_URI

Local repair endpoint

-c, --control=ENDPOINT_URI

Local control endpoint


IPv4 or IPv6 address of the network interface on which to join the multicast group


enable SO_REUSEADDR when binding sockets


Session target latency, TIME units


Session minimum latency, TIME units


Session maximum latency, TIME units


Playback target latency, TIME units


Session no playback timeout, TIME units


Session broken playback timeout, TIME units


Session breakage detection window, TIME units


Maximum packet size, in bytes


Maximum internal frame size, in bytes


Duration of the internal frames, TIME units


Override output sample rate, Hz


Disable resampling (default=off)


Resampler backend (possible values=”default”, “builtin”, “speex” default=`default’)


Resampler profile (possible values=”low”, “medium”, “high” default=`medium’)

-1, --oneshot

Exit when last connected client disconnects (default=off)


Enable uninitialized memory poisoning (default=off)


Enable self profiling (default=off)


Enable beeping on packet loss (default=off)


Set colored logging mode for stderr output (possible values=”auto”, “always”, “never” default=`auto’)

Endpoint URI

--source, --repair, and --control options define network endpoints on which to receive the traffic.

ENDPOINT_URI should have the following form:



  • rtsp://localhost:123/path?query

  • rtp+rs8m://localhost:123

  • rtp://

  • rtp://[::1]:123

  • rtcp://

The list of supported protocols can be retrieved using --list-supported option.

The host field should be either FQDN (domain name), or IPv4 address, or IPv6 address in square brackets. It may be (for IPv4) or [::] (for IPv6) to bind endpoint to all network interfaces.

The port field can be omitted if the protocol defines standard port. Otherwise, it is mandatory. It may be set to zero to bind endpoint to a radomly chosen ephemeral port.

The path and query fields are allowed only for protocols that support them, e.g. for RTSP.

If FEC is enabled on sender, a pair of a source and repair endpoints should be provided. The two endpoints should use compatible protocols, e.g. rtp+rs8m:// for source endpoint, and rs8m:// for repair endpoint. If FEC is disabled, a single source endpoint should be provided.

Supported source and repair protocols:

  • source rtp://, repair none (bare RTP without FEC)

  • source rtp+rs8m://, repair rs8m:// (RTP with Reed-Solomon FEC)

  • source rtp+ldpc://, repair ldpc:// (RTP with LDPC-Staircase FEC)

In addition, it is recommended to provide control endpoint. It is used to exchange non-media information used to identify session, carry feedback, etc. If no control endpoint is provided, session operates in reduced fallback mode, which may be less robust and may not support all features.

Supported control protocols:

  • rtcp://


--output and --backup options require a device or file URI in one of the following forms:

  • DEVICE_TYPE://DEVICE_NAME – audio device

  • DEVICE_TYPE://default – default audio device for given device type

  • file:///ABS/PATH – absolute file path

  • file://localhost/ABS/PATH – absolute file path (alternative form; only “localhost” host is supported)

  • file:/ABS/PATH – absolute file path (alternative form)

  • file:REL/PATH – relative file path

  • file://- – stdout

  • file:- – stdout (alternative form)


  • pulse://default

  • pulse://alsa_output.pci-0000_00_1f.3.analog-stereo

  • alsa://hw:1,0

  • file:///home/user/test.wav

  • file://localhost/home/user/test.wav

  • file:/home/user/test.wav

  • file:./test.wav

  • file:-

The list of supported schemes and file formats can be retrieved using --list-supported option.

If the --output is omitted, the default driver and device are selected. If the --backup is omitted, no backup source is used.

The --output-format and --backup-format options can be used to force the output or backup file format. If the option is omitted, the file format is auto-detected. The option is always required when the output or backup is stdout or stdin.

The path component of the provided URI is percent-decoded. For convenience, unencoded characters are allowed as well, except that % should be always encoded as %25.

For example, the file named /foo/bar%/[baz] may be specified using either of the following URIs: file:///foo%2Fbar%25%2F%5Bbaz%5D and file:///foo/bar%25/[baz].

Multicast interface

If --miface option is present, it defines an IP address of the network interface on which to join the multicast group. If not present, no multicast group should be joined.

It’s not possible to receive multicast traffic without joining a multicast group. The user should either provide multicast interface, or join the group manually using foreign tools.

MIFACE should be an IP address of the network interface on which to join the multicast group. It may be (for IPv4) or :: (for IPv6) to join the multicast group on all available interfaces.

Multiple slots

Multiple sets of endpoints can be specified to retrieve media from multiple addresses.

Such endpoint sets are called slots. All slots should have the same set of endpoint types (source, repair, etc) and should use the same protocols for them. All slots should also have their own multicast interface option, if it’s used.


If --reuseaddr option is provided, SO_REUSEADDR socket option will be enabled for all sockets (by default it’s enabled only for multicast sockets).

For TCP, it allows immediately reusing recently closed socket in TIME_WAIT state, which may be useful you want to be able to restart server quickly.

For UDP, it allows multiple processes to bind to the same address, which may be useful if you’re using systemd socket activation.

Regardless of the option, SO_REUSEADDR is always disabled when binding to ephemeral port.

Backup audio

If --backup option is given, it defines input audio device or file which will be played when there are no connected sessions. If it’s not given, silence is played instead.

Backup file is restarted from the beginning each time when the last session disconnect. The playback of of the backup file is automatically looped.

Time units

TIME should have one of the following forms:

123ns, 123us, 123ms, 123s, 123m, 123h


Endpoint examples

Bind one bare RTP endpoint on all IPv4 interfaces:

$ roc-recv -vv -s rtp://

Bind two source and repair endpoints to all IPv4 interfaces (but not IPv6):

$ roc-recv -vv -s rtp+rs8m:// -r rs8m://

Bind two source and repair endpoints to all IPv6 interfaces (but not IPv4):

$ roc-recv -vv -s rtp+rs8m://[::]:10001 -r rs8m://[::]:10002

Bind two source and repair endpoints to a particular network interface:

$ roc-recv -vv -s rtp+rs8m:// -r rs8m://

Bind three source, repair, and control endpoints:

$ roc-recv -vv \
    -s rtp+rs8m:// -r rs8m:// -c rtcp://

Bind two source and repair endpoints to a particular multicast address and join to a multicast group on a particular network interface:

$ roc-recv -vv -s rtp+rs8m:// -r rs8m:// --miface

Bind two sets of source, repair, and control endpoints:

$ roc-recv -vv \
    -s rtp+rs8m:// -r rs8m:// -c rtcp:// \
    -s rtp+rs8m:// -r rs8m:// -c rtcp://

I/O examples

Output to the default ALSA device:

$ roc-recv -vv -s rtp:// -o alsa://default

Output to a specific PulseAudio device:

$ roc-recv -vv -s rtp:// -o pulse://alsa_input.pci-0000_00_1f.3.analog-stereo

Output to a file in WAV format (guess format by extension):

$ roc-recv -vv -s rtp:// -o file:./output.wav

Output to a file in WAV format (specify format manually):

$ roc-recv -vv -s rtp:// -o file:./output --output-format wav

Output to stdout in WAV format:

$ roc-recv -vv -s rtp:// -o file:- --output-format wav >./output.wav

Output to a file in WAV format (absolute path):

$ roc-recv -vv -s rtp:// -o file:///home/user/output.wav

Specify backup file:

$ roc-recv -vv -s rtp:// --backup file:./backup.wav

Tuning examples

Force a specific rate on the output device:

$ roc-recv -vv -s rtp:// --rate=44100

Select the LDPC-Staircase FEC scheme:

$ roc-recv -vv -s rtp+ldpc:// -r ldpc://

Select higher session latency and timeouts:

$ roc-recv -vv -s rtp:// \
    --sess-latency=5s --min-latency=-1s --max-latency=10s --np-timeout=10s --bp-timeout=10s

Select higher I/O latency:

$ roc-recv -vv -s rtp:// \

Select resampler profile:

$ roc-recv -vv -s rtp:// \


roc-send(1), and the Roc web site at


Please report any bugs found via GitHub (


See authors page on the website for a list of maintainers and contributors.