| FFMPEG-RESAMPLER(1) FFMPEG-RESAMPLER(1) | |
| NAME | |
| ffmpeg-resampler - FFmpeg Resampler | |
| 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. | |
| RESAMPLER OPTIONS | |
| The audio resampler supports the following named options. | |
| Options may be set by specifying -option value in the FFmpeg tools, | |
| option=value for the aresample filter, by setting the value explicitly | |
| in the "SwrContext" options or using the libavutil/opt.h API for | |
| programmatic use. | |
| uchl, used_chlayout | |
| Set used input channel layout. Default is unset. This option is | |
| only used for special remapping. | |
| isr, in_sample_rate | |
| Set the input sample rate. Default value is 0. | |
| osr, out_sample_rate | |
| Set the output sample rate. Default value is 0. | |
| isf, in_sample_fmt | |
| Specify the input sample format. It is set by default to "none". | |
| osf, out_sample_fmt | |
| Specify the output sample format. It is set by default to "none". | |
| tsf, internal_sample_fmt | |
| Set the internal sample format. Default value is "none". This will | |
| automatically be chosen when it is not explicitly set. | |
| ichl, in_chlayout | |
| ochl, out_chlayout | |
| Set the input/output channel layout. | |
| See the Channel Layout section in the ffmpeg-utils(1) manual for | |
| the required syntax. | |
| clev, center_mix_level | |
| Set the center mix level. It is a value expressed in deciBel, and | |
| must be in the interval [-32,32]. | |
| slev, surround_mix_level | |
| Set the surround mix level. It is a value expressed in deciBel, and | |
| must be in the interval [-32,32]. | |
| lfe_mix_level | |
| Set LFE mix into non LFE level. It is used when there is a LFE | |
| input but no LFE output. It is a value expressed in deciBel, and | |
| must be in the interval [-32,32]. | |
| rmvol, rematrix_volume | |
| Set rematrix volume. Default value is 1.0. | |
| 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. | |
| flags, swr_flags | |
| Set flags used by the converter. Default value is 0. | |
| It supports the following individual flags: | |
| res force resampling, this flag forces resampling to be used even | |
| when the input and output sample rates match. | |
| dither_scale | |
| Set the dither scale. Default value is 1. | |
| dither_method | |
| Set dither method. Default value is 0. | |
| Supported values: | |
| rectangular | |
| select rectangular dither | |
| triangular | |
| select triangular dither | |
| triangular_hp | |
| select triangular dither with high pass | |
| lipshitz | |
| select Lipshitz noise shaping dither. | |
| shibata | |
| select Shibata noise shaping dither. | |
| low_shibata | |
| select low Shibata noise shaping dither. | |
| high_shibata | |
| select high Shibata noise shaping dither. | |
| f_weighted | |
| select f-weighted noise shaping dither | |
| modified_e_weighted | |
| select modified-e-weighted noise shaping dither | |
| improved_e_weighted | |
| select improved-e-weighted noise shaping dither | |
| resampler | |
| Set resampling engine. Default value is swr. | |
| Supported values: | |
| swr select the native SW Resampler; filter options precision and | |
| cheby are not applicable in this case. | |
| 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. | |
| filter_size | |
| For swr only, set resampling filter size, default value is 32. | |
| phase_shift | |
| For swr only, set resampling phase shift, default value is 10, and | |
| must be in the interval [0,30]. | |
| linear_interp | |
| Use linear interpolation when enabled (the default). Disable it if | |
| you want to preserve speed instead of quality when exact_rational | |
| fails. | |
| 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 "1 << | |
| phase_shift", the phase_count will be "1 << phase_shift" as | |
| fallback. Default is enabled. | |
| 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). | |
| 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'. | |
| cheby | |
| For soxr only, selects passband rolloff none (Chebyshev) & higher- | |
| precision approximation for 'irrational' ratios. Default value is | |
| 0. | |
| 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. | |
| 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. | |
| 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 | |
| (min_comp = "FLT_MAX"). | |
| 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 min_comp. The default is 0.1. | |
| 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. | |
| 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. | |
| matrix_encoding | |
| Select matrixed stereo encoding. | |
| It accepts the following values: | |
| none | |
| select none | |
| dolby | |
| select Dolby | |
| dplii | |
| select Dolby Pro Logic II | |
| Default value is "none". | |
| filter_type | |
| For swr only, select resampling filter type. This only affects | |
| resampling operations. | |
| It accepts the following values: | |
| cubic | |
| select cubic | |
| blackman_nuttall | |
| select Blackman Nuttall windowed sinc | |
| kaiser | |
| select Kaiser windowed sinc | |
| 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. | |
| 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. | |
| SEE ALSO | |
| ffmpeg(1), ffplay(1), ffprobe(1), libswresample(3) | |
| AUTHORS | |
| The FFmpeg developers. | |
| For details about the authorship, see the Git history of the project | |
| (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command git log in | |
| the FFmpeg source directory, or browsing the online repository at | |
| <https://git.ffmpeg.org/ffmpeg>. | |
| Maintainers for the specific components are listed in the file | |
| MAINTAINERS in the source code tree. | |
| FFMPEG-RESAMPLER(1) | |