(ffmpeg-utils)2.8. Syntax | Channel Layout

doc

Channel Layout

Official documentation says:

A channel layout specifies the spatial disposition of the channels in a multi-channel audio stream. To specify a channel layout, FFmpeg makes use of a special syntax.

Individual channels are identified by an id, as given by the table below:

id	meaning
FL	front left
FR	front right
FC	front center
LFE	low frequency
BL	back left
BR	back right
FLC	front left-of-center
FRC	front right-of-center
BC	back center
SL	side left
SR	side right
TC	top center
TFL	top front left
TFC	top front center
TFR	top front right
TBL	top back left
TBC	top back center
TBR	top back right
DL	downmix left
DR	downmix right
WL	wide left
WR	wide right
SDL	surround direct left
SDR	surround direct right
LFE2	low frequency 2

Standard channel layout compositions can be specified by using the following identifiers:

id	meaning
mono	FC
stereo	FL+FR
2.1	FL+FR+LFE
3.0	FL+FR+FC
3.0(back)	FL+FR+BC
4.0	FL+FR+FC+BC
quad	FL+FR+BL+BR
quad(side)	FL+FR+SL+SR
3.1	FL+FR+FC+LFE
5.0	FL+FR+FC+BL+BR
5.0(side)	FL+FR+FC+SL+SR
4.1	FL+FR+FC+LFE+BC
5.1	FL+FR+FC+LFE+BL+BR
5.1(side)	FL+FR+FC+LFE+SL+SR
6.0	FL+FR+FC+BC+SL+SR
6.0(front)	FL+FR+FLC+FRC+SL+SR
hexagonal	FL+FR+FC+BL+BR+BC
6.1	FL+FR+FC+LFE+BC+SL+SR
6.1	FL+FR+FC+LFE+BL+BR+BC
6.1(front)	FL+FR+LFE+FLC+FRC+SL+SR
7.0	FL+FR+FC+BL+BR+SL+SR
7.0(front)	FL+FR+FC+FLC+FRC+SL+SR
7.1	FL+FR+FC+LFE+BL+BR+SL+SR
7.1(wide)	FL+FR+FC+LFE+BL+BR+FLC+FRC
7.1(wide-side)	FL+FR+FC+LFE+FLC+FRC+SL+SR
octagonal	FL+FR+FC+BL+BR+BC+SL+SR
hexadecagonal	FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR
downmix	DL+DR

A custom channel layout can be specified as a sequence of terms, separated by + or |. Each term can be:

• the name of a standard channel layout (e.g. mono, stereo, 4.0, quad, 5.0, etc.)

• the name of a single channel (e.g. FL, FR, FC, LFE, etc.)

• a number of channels, in decimal, followed by c, yielding the default channel layout for that number of channels (see the function av_get_default_channel_layout). Note that not all channel counts have a default layout.

• a number of channels, in decimal, followed by C, yielding an unknown channel layout with the specified number of channels. Note that not all channel layout specification strings support unknown channel layouts.

• a channel layout mask, in hexadecimal starting with 0x (see the AV_CH_* macros in libavutil/channel_layout.h.

Before libavutil version 53 the trailing character c to specify a number of channels was optional, but now it is required, while a channel layout mask can also be specified as a decimal number (if and only if not followed by c or C).

See also the function av_get_channel_layout defined in libavutil/channel_layout.h.

[me@host: ~]$ # specify channel layout to anullsrc
[me@host: ~]$ ffplay -f lavfi anullsrc=r=48000:cl=stereo

[me@host: ~]$ # pan audio
[me@host: ~]$ ffplay audio.wav -af "pan='stereo|FL=FR|FR=FL'"