| \input texinfo @c -*- texinfo -*- |
| |
| @settitle FFmpeg Resampler Documentation |
| @titlepage |
| @center @titlefont{FFmpeg Resampler Documentation} |
| @end titlepage |
| |
| @top |
| |
| @contents |
| |
| @chapter Description |
| @c man begin DESCRIPTION |
| |
| The FFmpeg resampler provides an 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. |
| |
| @c man end DESCRIPTION |
| |
| @chapter Resampler Options |
| @c man begin RESAMPLER OPTIONS |
| |
| The audio resampler supports the following named options. |
| |
| Options may be set by specifying -@var{option} @var{value} in the |
| FFmpeg tools, @var{option}=@var{value} for the aresample filter, |
| by setting the value explicitly in the |
| @code{SwrContext} options or using the @file{libavutil/opt.h} API for |
| programmatic use. |
| |
| @table @option |
| |
| @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 |
| @option{in_channel_layout} is set. |
| |
| @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 |
| @option{out_channel_layout} is set. |
| |
| @item uch, used_channel_count |
| Set the number of used channels. Default value is 0. This option is |
| only used for special remapping. |
| |
| @item isr, in_sample_rate |
| Set the input sample rate. Default value is 0. |
| |
| @item osr, out_sample_rate |
| Set the output sample rate. Default value is 0. |
| |
| @item isf, in_sample_fmt |
| Specify the input sample format. It is set by default to @code{none}. |
| |
| @item osf, out_sample_fmt |
| Specify the output sample format. It is set by default to @code{none}. |
| |
| @item tsf, internal_sample_fmt |
| Set the internal sample format. Default value is @code{none}. |
| |
| @item icl, in_channel_layout |
| Set the input channel layout. |
| |
| @item ocl, out_channel_layout |
| Set the output channel layout. |
| |
| @item clev, center_mix_level |
| Set center mix level. It is a value expressed in deciBel, and must be |
| inclusively included between -32 and +32. |
| |
| @item slev, surround_mix_level |
| Set surround mix level. It is a value expressed in deciBel, and must |
| be inclusively included between -32 and +32. |
| |
| @item lfe_mix_evel |
| Set LFE mix level. |
| |
| @item rmvol, rematrix_volume |
| Set rematrix volume. Default value is 1.0. |
| |
| @item flags, swr_flags |
| Set flags used by the converter. Default value is 0. |
| |
| It supports the following individual flags: |
| @table @option |
| @item res |
| force resampling |
| @end table |
| |
| @item dither_scale |
| Set the dither scale. Default value is 1. |
| |
| @item dither_method |
| Set dither method. Default value is 0. |
| |
| Supported values: |
| @table @samp |
| @item rectangular |
| select rectangular dither |
| @item triangular |
| select triangular dither |
| @item triangular_hp |
| select triangular dither with high pass |
| @end table |
| |
| @item resampler |
| Set resampling engine. Default value is swr. |
| |
| Supported values: |
| @table @samp |
| @item swr |
| select the native SW Resampler; filter options precision and cheby are not |
| applicable in this case. |
| @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. |
| @end table |
| |
| @item filter_size |
| For swr only, set resampling filter size, default value is 32. |
| |
| @item phase_shift |
| For swr only, set resampling phase shift, default value is 10, must be included |
| between 0 and 30. |
| |
| @item linear_interp |
| Use Linear Interpolation if set to 1, default value is 0. |
| |
| @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). |
| |
| @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'. |
| |
| @item cheby |
| For soxr only, selects passband rolloff none (Chebyshev) & higher-precision |
| approximation for 'irrational' ratios. Default value is 0. |
| |
| @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. |
| |
| @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 |
| (@option{min_comp} = @code{FLT_MAX}). |
| |
| @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 @option{min_comp}. |
| The default is 0.1. |
| |
| @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. |
| |
| @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. |
| |
| @item matrix_encoding |
| Select matrixed stereo encoding. |
| |
| It accepts the following values: |
| @table @samp |
| @item none |
| select none |
| @item dolby |
| select Dolby |
| @item dplii |
| select Dolby Pro Logic II |
| @end table |
| |
| Default value is @code{none}. |
| |
| @item filter_type |
| For swr only, select resampling filter type. This only affects resampling |
| operations. |
| |
| It accepts the following values: |
| @table @samp |
| @item cubic |
| select cubic |
| @item blackman_nuttall |
| select Blackman Nuttall Windowed Sinc |
| @item kaiser |
| select Kaiser Windowed Sinc |
| @end table |
| |
| @item kaiser_beta |
| For swr only, set Kaiser Window Beta value. Must be an integer included between |
| 2 and 16, default value is 9. |
| |
| @end table |
| |
| @c man end RESAMPLER OPTIONS |
| |
| @chapter See Also |
| |
| @ifhtml |
| @url{ffmpeg.html,ffmpeg}, @url{ffplay.html,ffplay}, @url{ffprobe.html,ffprobe}, @url{ffserver.html,ffserver}, |
| @url{libswresample.html,libswresample} |
| @end ifhtml |
| |
| @ifnothtml |
| ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libswresample(3) |
| @end ifnothtml |
| |
| @include authors.texi |
| |
| @ignore |
| |
| @setfilename ffmpeg-resampler |
| @settitle FFmpeg Resampler |
| |
| @end ignore |
| |
| @bye |