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.\"

.IX Title "FFMPEG-RESAMPLER 1"

.TH FFMPEG-RESAMPLER 1 "2013-12-14" " " " "

.SH "NAME"

ffmpeg\-resampler \- FFmpeg Resampler

.SH "DESCRIPTION"

.IX Header "DESCRIPTION"

The FFmpeg resampler provides a high-level interface to the

libswresample library audio resampling utilities. In particular it

allows to perform audio resampling, audio channel layout rematrixing,

and convert audio format and packing layout.

.SH "RESAMPLER OPTIONS"

.IX Header "RESAMPLER OPTIONS"

The audio resampler supports the following named options.

.PP

Options may be set by specifying \-\fIoption\fR \fIvalue\fR in the

FFmpeg tools, \fIoption\fR=\fIvalue\fR for the aresample filter,

by setting the value explicitly in the

\&\f(CW\*(C`SwrContext\*(C'\fR options or using the \fIlibavutil/opt.h\fR \s-1API\s0 for

programmatic use.

.IP "\fBich, in_channel_count\fR" 4

.IX Item "ich, in_channel_count"

Set the number of input channels. Default value is 0. Setting this

value is not mandatory if the corresponding channel layout

\&\fBin_channel_layout\fR is set.

.IP "\fBoch, out_channel_count\fR" 4

.IX Item "och, out_channel_count"

Set the number of output channels. Default value is 0. Setting this

value is not mandatory if the corresponding channel layout

\&\fBout_channel_layout\fR is set.

.IP "\fBuch, used_channel_count\fR" 4

.IX Item "uch, used_channel_count"

Set the number of used input channels. Default value is 0. This option is

only used for special remapping.

.IP "\fBisr, in_sample_rate\fR" 4

.IX Item "isr, in_sample_rate"

Set the input sample rate. Default value is 0.

.IP "\fBosr, out_sample_rate\fR" 4

.IX Item "osr, out_sample_rate"

Set the output sample rate. Default value is 0.

.IP "\fBisf, in_sample_fmt\fR" 4

.IX Item "isf, in_sample_fmt"

Specify the input sample format. It is set by default to \f(CW\*(C`none\*(C'\fR.

.IP "\fBosf, out_sample_fmt\fR" 4

.IX Item "osf, out_sample_fmt"

Specify the output sample format. It is set by default to \f(CW\*(C`none\*(C'\fR.

.IP "\fBtsf, internal_sample_fmt\fR" 4

.IX Item "tsf, internal_sample_fmt"

Set the internal sample format. Default value is \f(CW\*(C`none\*(C'\fR.

This will automatically be chosen when it is not explicitly set.

.IP "\fBicl, in_channel_layout\fR" 4

.IX Item "icl, in_channel_layout"

.PD 0

.IP "\fBocl, out_channel_layout\fR" 4

.IX Item "ocl, out_channel_layout"

.PD

Set the input/output channel layout.

.Sp

See the Channel Layout section in the \fIffmpeg\-utils\fR\|(1) manual

for the required syntax.

.IP "\fBclev, center_mix_level\fR" 4

.IX Item "clev, center_mix_level"

Set the center mix level. It is a value expressed in deciBel, and must be

in the interval [\-32,32].

.IP "\fBslev, surround_mix_level\fR" 4

.IX Item "slev, surround_mix_level"

Set the surround mix level. It is a value expressed in deciBel, and must

be in the interval [\-32,32].

.IP "\fBlfe_mix_level\fR" 4

.IX Item "lfe_mix_level"

Set \s-1LFE\s0 mix into non \s-1LFE\s0 level. It is used when there is a \s-1LFE\s0 input but no

\&\s-1LFE\s0 output. It is a value expressed in deciBel, and must

be in the interval [\-32,32].

.IP "\fBrmvol, rematrix_volume\fR" 4

.IX Item "rmvol, rematrix_volume"

Set rematrix volume. Default value is 1.0.

.IP "\fBrematrix_maxval\fR" 4

.IX Item "rematrix_maxval"

Set maximum output value for rematrixing.

This can be used to prevent clipping vs. preventing volumn reduction

A value of 1.0 prevents cliping.

.IP "\fBflags, swr_flags\fR" 4

.IX Item "flags, swr_flags"

Set flags used by the converter. Default value is 0.

.Sp

It supports the following individual flags:

.RS 4

.IP "\fBres\fR" 4

.IX Item "res"

force resampling, this flag forces resampling to be used even when the

input and output sample rates match.

.RE

.RS 4

.RE

.IP "\fBdither_scale\fR" 4

.IX Item "dither_scale"

Set the dither scale. Default value is 1.

.IP "\fBdither_method\fR" 4

.IX Item "dither_method"

Set dither method. Default value is 0.

.Sp

Supported values:

.RS 4

.IP "\fBrectangular\fR" 4

.IX Item "rectangular"

select rectangular dither

.IP "\fBtriangular\fR" 4

.IX Item "triangular"

select triangular dither

.IP "\fBtriangular_hp\fR" 4

.IX Item "triangular_hp"

select triangular dither with high pass

.IP "\fBlipshitz\fR" 4

.IX Item "lipshitz"

select lipshitz noise shaping dither

.IP "\fBshibata\fR" 4

.IX Item "shibata"

select shibata noise shaping dither

.IP "\fBlow_shibata\fR" 4

.IX Item "low_shibata"

select low shibata noise shaping dither

.IP "\fBhigh_shibata\fR" 4

.IX Item "high_shibata"

select high shibata noise shaping dither

.IP "\fBf_weighted\fR" 4

.IX Item "f_weighted"

select f\-weighted noise shaping dither

.IP "\fBmodified_e_weighted\fR" 4

.IX Item "modified_e_weighted"

select modified-e-weighted noise shaping dither

.IP "\fBimproved_e_weighted\fR" 4

.IX Item "improved_e_weighted"

select improved-e-weighted noise shaping dither

.RE

.RS 4

.RE

.IP "\fBresampler\fR" 4

.IX Item "resampler"

Set resampling engine. Default value is swr.

.Sp

Supported values:

.RS 4

.IP "\fBswr\fR" 4

.IX Item "swr"

select the native \s-1SW\s0 Resampler; filter options precision and cheby are not

applicable in this case.

.IP "\fBsoxr\fR" 4

.IX Item "soxr"

select the SoX Resampler (where available); compensation, and filter options

filter_size, phase_shift, filter_type & kaiser_beta, are not applicable in this

case.

.RE

.RS 4

.RE

.IP "\fBfilter_size\fR" 4

.IX Item "filter_size"

For swr only, set resampling filter size, default value is 32.

.IP "\fBphase_shift\fR" 4

.IX Item "phase_shift"

For swr only, set resampling phase shift, default value is 10, and must be in

the interval [0,30].

.IP "\fBlinear_interp\fR" 4

.IX Item "linear_interp"

Use Linear Interpolation if set to 1, default value is 0.

.IP "\fBcutoff\fR" 4

.IX Item "cutoff"

Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must be a float

value between 0 and 1.  Default value is 0.97 with swr, and 0.91 with soxr

(which, with a sample-rate of 44100, preserves the entire audio band to 20kHz).

.IP "\fBprecision\fR" 4

.IX Item "precision"

For soxr only, the precision in bits to which the resampled signal will be

calculated.  The default value of 20 (which, with suitable dithering, is

appropriate for a destination bit-depth of 16) gives SoX's 'High Quality'; a

value of 28 gives SoX's 'Very High Quality'.

.IP "\fBcheby\fR" 4

.IX Item "cheby"

For soxr only, selects passband rolloff none (Chebyshev) & higher-precision

approximation for 'irrational' ratios. Default value is 0.

.IP "\fBasync\fR" 4

.IX Item "async"

For swr only, simple 1 parameter audio sync to timestamps using stretching,

squeezing, filling and trimming. Setting this to 1 will enable filling and

trimming, larger values represent the maximum amount in samples that the data

may be stretched or squeezed for each second.

Default value is 0, thus no compensation is applied to make the samples match

the audio timestamps.

.IP "\fBfirst_pts\fR" 4

.IX Item "first_pts"

For swr only, assume the first pts should be this value. The time unit is 1 / sample rate.

This allows for padding/trimming at the start of stream. By default, no

assumption is made about the first frame's expected pts, so no padding or

trimming is done. For example, this could be set to 0 to pad the beginning with

silence if an audio stream starts after the video stream or to trim any samples

with a negative pts due to encoder delay.

.IP "\fBmin_comp\fR" 4

.IX Item "min_comp"

For swr only, set the minimum difference between timestamps and audio data (in

seconds) to trigger stretching/squeezing/filling or trimming of the

data to make it match the timestamps. The default is that

stretching/squeezing/filling and trimming is disabled

(\fBmin_comp\fR = \f(CW\*(C`FLT_MAX\*(C'\fR).

.IP "\fBmin_hard_comp\fR" 4

.IX Item "min_hard_comp"

For swr only, set the minimum difference between timestamps and audio data (in

seconds) to trigger adding/dropping samples to make it match the

timestamps.  This option effectively is a threshold to select between

hard (trim/fill) and soft (squeeze/stretch) compensation. Note that

all compensation is by default disabled through \fBmin_comp\fR.

The default is 0.1.

.IP "\fBcomp_duration\fR" 4

.IX Item "comp_duration"

For swr only, set duration (in seconds) over which data is stretched/squeezed

to make it match the timestamps. Must be a non-negative double float value,

default value is 1.0.

.IP "\fBmax_soft_comp\fR" 4

.IX Item "max_soft_comp"

For swr only, set maximum factor by which data is stretched/squeezed to make it

match the timestamps. Must be a non-negative double float value, default value

is 0.

.IP "\fBmatrix_encoding\fR" 4

.IX Item "matrix_encoding"

Select matrixed stereo encoding.

.Sp

It accepts the following values:

.RS 4

.IP "\fBnone\fR" 4

.IX Item "none"

select none

.IP "\fBdolby\fR" 4

.IX Item "dolby"

select Dolby

.IP "\fBdplii\fR" 4

.IX Item "dplii"

select Dolby Pro Logic \s-1II\s0

.RE

.RS 4

.Sp

Default value is \f(CW\*(C`none\*(C'\fR.

.RE

.IP "\fBfilter_type\fR" 4

.IX Item "filter_type"

For swr only, select resampling filter type. This only affects resampling

operations.

.Sp

It accepts the following values:

.RS 4

.IP "\fBcubic\fR" 4

.IX Item "cubic"

select cubic

.IP "\fBblackman_nuttall\fR" 4

.IX Item "blackman_nuttall"

select Blackman Nuttall Windowed Sinc

.IP "\fBkaiser\fR" 4

.IX Item "kaiser"

select Kaiser Windowed Sinc

.RE

.RS 4

.RE

.IP "\fBkaiser_beta\fR" 4

.IX Item "kaiser_beta"

For swr only, set Kaiser Window Beta value. Must be an integer in the

interval [2,16], default value is 9.

.IP "\fBoutput_sample_bits\fR" 4

.IX Item "output_sample_bits"

For swr only, set number of used output sample bits for dithering. Must be an integer in the

interval [0,64], default value is 0, which means it's not used.

.SH "SEE ALSO"

.IX Header "SEE ALSO"

\&\fIffmpeg\fR\|(1), \fIffplay\fR\|(1), \fIffprobe\fR\|(1), \fIffserver\fR\|(1), \fIlibswresample\fR\|(3)

.SH "AUTHORS"

.IX Header "AUTHORS"

The FFmpeg developers.

.PP

For details about the authorship, see the Git history of the project

(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command

\&\fBgit log\fR in the FFmpeg source directory, or browsing the

online repository at <\fBhttp://source.ffmpeg.org\fR>.

.PP

Maintainers for the specific components are listed in the file

\&\fI\s-1MAINTAINERS\s0\fR in the source code tree.