1FFMPEG-RESAMPLER(1)                                        FFMPEG-RESAMPLER(1)
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NAME

6       ffmpeg-resampler - FFmpeg Resampler
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DESCRIPTION

9       The FFmpeg resampler provides a high-level interface to the
10       libswresample library audio resampling utilities. In particular it
11       allows one to perform audio resampling, audio channel layout
12       rematrixing, and convert audio format and packing layout.
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RESAMPLER OPTIONS

15       The audio resampler supports the following named options.
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17       Options may be set by specifying -option value in the FFmpeg tools,
18       option=value for the aresample filter, by setting the value explicitly
19       in the "SwrContext" options or using the libavutil/opt.h API for
20       programmatic use.
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22       ich, in_channel_count
23           Set the number of input channels. Default value is 0. Setting this
24           value is not mandatory if the corresponding channel layout
25           in_channel_layout is set.
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27       och, out_channel_count
28           Set the number of output channels. Default value is 0. Setting this
29           value is not mandatory if the corresponding channel layout
30           out_channel_layout is set.
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32       uch, used_channel_count
33           Set the number of used input channels. Default value is 0. This
34           option is only used for special remapping.
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36       isr, in_sample_rate
37           Set the input sample rate. Default value is 0.
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39       osr, out_sample_rate
40           Set the output sample rate. Default value is 0.
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42       isf, in_sample_fmt
43           Specify the input sample format. It is set by default to "none".
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45       osf, out_sample_fmt
46           Specify the output sample format. It is set by default to "none".
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48       tsf, internal_sample_fmt
49           Set the internal sample format. Default value is "none".  This will
50           automatically be chosen when it is not explicitly set.
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52       icl, in_channel_layout
53       ocl, out_channel_layout
54           Set the input/output channel layout.
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56           See the Channel Layout section in the ffmpeg-utils(1) manual for
57           the required syntax.
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59       clev, center_mix_level
60           Set the center mix level. It is a value expressed in deciBel, and
61           must be in the interval [-32,32].
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63       slev, surround_mix_level
64           Set the surround mix level. It is a value expressed in deciBel, and
65           must be in the interval [-32,32].
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67       lfe_mix_level
68           Set LFE mix into non LFE level. It is used when there is a LFE
69           input but no LFE output. It is a value expressed in deciBel, and
70           must be in the interval [-32,32].
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72       rmvol, rematrix_volume
73           Set rematrix volume. Default value is 1.0.
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75       rematrix_maxval
76           Set maximum output value for rematrixing.  This can be used to
77           prevent clipping vs. preventing volume reduction.  A value of 1.0
78           prevents clipping.
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80       flags, swr_flags
81           Set flags used by the converter. Default value is 0.
82
83           It supports the following individual flags:
84
85           res force resampling, this flag forces resampling to be used even
86               when the input and output sample rates match.
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88       dither_scale
89           Set the dither scale. Default value is 1.
90
91       dither_method
92           Set dither method. Default value is 0.
93
94           Supported values:
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96           rectangular
97               select rectangular dither
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99           triangular
100               select triangular dither
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102           triangular_hp
103               select triangular dither with high pass
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105           lipshitz
106               select Lipshitz noise shaping dither.
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108           shibata
109               select Shibata noise shaping dither.
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111           low_shibata
112               select low Shibata noise shaping dither.
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114           high_shibata
115               select high Shibata noise shaping dither.
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117           f_weighted
118               select f-weighted noise shaping dither
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120           modified_e_weighted
121               select modified-e-weighted noise shaping dither
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123           improved_e_weighted
124               select improved-e-weighted noise shaping dither
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126       resampler
127           Set resampling engine. Default value is swr.
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129           Supported values:
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131           swr select the native SW Resampler; filter options precision and
132               cheby are not applicable in this case.
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134           soxr
135               select the SoX Resampler (where available); compensation, and
136               filter options filter_size, phase_shift, exact_rational,
137               filter_type & kaiser_beta, are not applicable in this case.
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139       filter_size
140           For swr only, set resampling filter size, default value is 32.
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142       phase_shift
143           For swr only, set resampling phase shift, default value is 10, and
144           must be in the interval [0,30].
145
146       linear_interp
147           Use linear interpolation when enabled (the default). Disable it if
148           you want to preserve speed instead of quality when exact_rational
149           fails.
150
151       exact_rational
152           For swr only, when enabled, try to use exact phase_count based on
153           input and output sample rate. However, if it is larger than "1 <<
154           phase_shift", the phase_count will be "1 << phase_shift" as
155           fallback. Default is enabled.
156
157       cutoff
158           Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must
159           be a float value between 0 and 1.  Default value is 0.97 with swr,
160           and 0.91 with soxr (which, with a sample-rate of 44100, preserves
161           the entire audio band to 20kHz).
162
163       precision
164           For soxr only, the precision in bits to which the resampled signal
165           will be calculated.  The default value of 20 (which, with suitable
166           dithering, is appropriate for a destination bit-depth of 16) gives
167           SoX's 'High Quality'; a value of 28 gives SoX's 'Very High
168           Quality'.
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170       cheby
171           For soxr only, selects passband rolloff none (Chebyshev) & higher-
172           precision approximation for 'irrational' ratios. Default value is
173           0.
174
175       async
176           For swr only, simple 1 parameter audio sync to timestamps using
177           stretching, squeezing, filling and trimming. Setting this to 1 will
178           enable filling and trimming, larger values represent the maximum
179           amount in samples that the data may be stretched or squeezed for
180           each second.  Default value is 0, thus no compensation is applied
181           to make the samples match the audio timestamps.
182
183       first_pts
184           For swr only, assume the first pts should be this value. The time
185           unit is 1 / sample rate.  This allows for padding/trimming at the
186           start of stream. By default, no assumption is made about the first
187           frame's expected pts, so no padding or trimming is done. For
188           example, this could be set to 0 to pad the beginning with silence
189           if an audio stream starts after the video stream or to trim any
190           samples with a negative pts due to encoder delay.
191
192       min_comp
193           For swr only, set the minimum difference between timestamps and
194           audio data (in seconds) to trigger stretching/squeezing/filling or
195           trimming of the data to make it match the timestamps. The default
196           is that stretching/squeezing/filling and trimming is disabled
197           (min_comp = "FLT_MAX").
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199       min_hard_comp
200           For swr only, set the minimum difference between timestamps and
201           audio data (in seconds) to trigger adding/dropping samples to make
202           it match the timestamps.  This option effectively is a threshold to
203           select between hard (trim/fill) and soft (squeeze/stretch)
204           compensation. Note that all compensation is by default disabled
205           through min_comp.  The default is 0.1.
206
207       comp_duration
208           For swr only, set duration (in seconds) over which data is
209           stretched/squeezed to make it match the timestamps. Must be a non-
210           negative double float value, default value is 1.0.
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212       max_soft_comp
213           For swr only, set maximum factor by which data is
214           stretched/squeezed to make it match the timestamps. Must be a non-
215           negative double float value, default value is 0.
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217       matrix_encoding
218           Select matrixed stereo encoding.
219
220           It accepts the following values:
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222           none
223               select none
224
225           dolby
226               select Dolby
227
228           dplii
229               select Dolby Pro Logic II
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231           Default value is "none".
232
233       filter_type
234           For swr only, select resampling filter type. This only affects
235           resampling operations.
236
237           It accepts the following values:
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239           cubic
240               select cubic
241
242           blackman_nuttall
243               select Blackman Nuttall windowed sinc
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245           kaiser
246               select Kaiser windowed sinc
247
248       kaiser_beta
249           For swr only, set Kaiser window beta value. Must be a double float
250           value in the interval [2,16], default value is 9.
251
252       output_sample_bits
253           For swr only, set number of used output sample bits for dithering.
254           Must be an integer in the interval [0,64], default value is 0,
255           which means it's not used.
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SEE ALSO

258       ffmpeg(1), ffplay(1), ffprobe(1), libswresample(3)
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AUTHORS

261       The FFmpeg developers.
262
263       For details about the authorship, see the Git history of the project
264       (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in
265       the FFmpeg source directory, or browsing the online repository at
266       <http://source.ffmpeg.org>.
267
268       Maintainers for the specific components are listed in the file
269       MAINTAINERS in the source code tree.
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273                                                           FFMPEG-RESAMPLER(1)
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