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| .\" | |
| .IX Title "FFMPEG-RESAMPLER 1" | |
| .TH FFMPEG-RESAMPLER 1 " " " " " " | |
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| .nh | |
| .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 one 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 "\fBuchl, used_chlayout\fR" 4 | |
| .IX Item "uchl, used_chlayout" | |
| Set used input channel layout. Default is unset. 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 "\fBichl, in_chlayout\fR" 4 | |
| .IX Item "ichl, in_chlayout" | |
| .PD 0 | |
| .IP "\fBochl, out_chlayout\fR" 4 | |
| .IX Item "ochl, out_chlayout" | |
| .PD | |
| Set the input/output channel layout. | |
| .Sp | |
| See \fBthe Channel Layout section in the \fBffmpeg\-utils\fB\|(1) manual\fR | |
| 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 volume reduction. | |
| A value of 1.0 prevents clipping. | |
| .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, exact_rational, 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 when enabled (the default). Disable it if you want | |
| to preserve speed instead of quality when exact_rational fails. | |
| .IP "\fBexact_rational\fR" 4 | |
| .IX Item "exact_rational" | |
| For swr only, when enabled, try to use exact phase_count based on input and | |
| output sample rate. However, if it is larger than \f(CW\*(C`1 << phase_shift\*(C'\fR, | |
| the phase_count will be \f(CW\*(C`1 << phase_shift\*(C'\fR as fallback. Default is enabled. | |
| .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 a double float value 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" | |
| \&\fBffmpeg\fR\|(1), \fBffplay\fR\|(1), \fBffprobe\fR\|(1), \fBlibswresample\fR\|(3) | |
| .SH "AUTHORS" | |
| .IX Header "AUTHORS" | |
| The FFmpeg developers. | |
| .PP | |
| For details about the authorship, see the Git history of the project | |
| (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command | |
| \&\fBgit log\fR in the FFmpeg source directory, or browsing the | |
| online repository at <\fBhttps://git.ffmpeg.org/ffmpeg\fR>. | |
| .PP | |
| Maintainers for the specific components are listed in the file | |
| \&\fI\s-1MAINTAINERS\s0\fR in the source code tree. | |