# Source: rpicam_options_libav.adoc

*Note: This file could not be automatically converted from AsciiDoc.*

=== `libav` options

The command line options specified in this section apply only to `libav` video backend.

To enable the `libav` backend, pass the xref:camera_software.adoc#codec[`codec`] option the value `libav`.

To pass one of the following options to an application, prefix the option name with `--`. If the option requires a value, pass the value immediately after the option name, separated by a single space. If the value contains a space, surround the value in quotes.

Some options have shorthand aliases, for example `-h` instead of `--help`. Use these shorthand aliases instead of the full option name to save space and time at the expense of readability.

==== `libav-format`

Sets the `libav` output format. Accepts the following values:

* `mkv` encoding
* `mp4` encoding
* `avi` encoding
* `h264` streaming
* `mpegts` streaming

If you do not provide this option, the file extension passed to the xref:camera_software.adoc#output[`output`] option determines the file format.

==== `libav-audio`

Enables audio recording. When enabled, you must also specify an xref:camera_software.adoc#audio-codec[`audio-codec`]. Does not accept a value.

==== `audio-codec`

Default value: `aac`

Selects an audio codec for output. For a list of available codecs, run `ffmpeg -codecs`.

==== `audio-bitrate`

Sets the bitrate for audio encoding in bits per second. Accepts numeric input.

Example: `rpicam-vid --codec libav -o test.mp4 --audio_codec mp2 --audio-bitrate 16384` (Records audio at 16 kilobits/sec with the mp2 codec)

==== `audio-samplerate`

Default value: `0`

Sets the audio sampling rate in Hz. Accepts numeric input. `0` uses the input sample rate.

==== `audio-device`

Select an ALSA input device for audio recording. For a list of available devices, run the following command:

[source,console]
----
$ pactl list | grep -A2 'Source #' | grep 'Name: '
----

You should see output similar to the following:

----
Name: alsa_output.platform-bcm2835_audio.analog-stereo.monitor
Name: alsa_output.platform-fef00700.hdmi.hdmi-stereo.monitor
Name: alsa_output.usb-GN_Netcom_A_S_Jabra_EVOLVE_LINK_000736B1214E0A-00.analog-stereo.monitor
Name: alsa_input.usb-GN_Netcom_A_S_Jabra_EVOLVE_LINK_000736B1214E0A-00.mono-fallback
----

==== `av-sync`

Shifts the audio sample timestamp by a value in microseconds. Accepts positive and negative numeric values.