From 8d9a50331322a93cdb4fc029825e5be1ffaef130 Mon Sep 17 00:00:00 2001 From: Rob Sykes Date: Thu, 27 Dec 2012 12:07:15 +0100 Subject: docs: add soxr documentation Signed-off-by: Michael Niedermayer --- doc/ffmpeg-resampler.texi | 55 ++++++++++++++++++++++++++++++++++------------- 1 file changed, 40 insertions(+), 15 deletions(-) (limited to 'doc/ffmpeg-resampler.texi') diff --git a/doc/ffmpeg-resampler.texi b/doc/ffmpeg-resampler.texi index 8470c042da..863253aaa7 100644 --- a/doc/ffmpeg-resampler.texi +++ b/doc/ffmpeg-resampler.texi @@ -106,29 +106,54 @@ select triangular dither 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 -Set resampling filter size, default value is 16. +For swr only, set resampling filter size, default value is 16. @item phase_shift -Set resampling phase shift, default value is 10, must be included +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 ratio. Must be a float value between 0 and 1, -default value is 0.8. +Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must be a float +value between 0 and 1. Default value is 0.8 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 min_comp -Set the minimum difference between timestamps and audio data (in +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 -Set the minimum difference between timestamps and audio data (in +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 @@ -136,14 +161,14 @@ all compensation is by default disabled through @option{min_comp}. The default is 0.1. @item comp_duration -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. +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 -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. +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. @@ -161,7 +186,7 @@ select Dolby Pro Logic II Default value is @code{none}. @item filter_type -Select resampling filter type. This only affects resampling +For swr only, select resampling filter type. This only affects resampling operations. It accepts the following values: @@ -175,8 +200,8 @@ select Kaiser Windowed Sinc @end table @item kaiser_beta -Set Kaiser Window Beta value. Must be an integer included between 2 -and 16, default value is 9. +For swr only, set Kaiser Window Beta value. Must be an integer included between +2 and 16, default value is 9. @end table -- cgit v1.2.3