forked from KolibriOS/kolibrios
404 lines
8.2 KiB
Plaintext
404 lines
8.2 KiB
Plaintext
=encoding utf8
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=head1 NAME
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ffmpeg-resampler - FFmpeg Resampler
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=head1 DESCRIPTION
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The FFmpeg resampler provides a high-level interface to the
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libswresample library audio resampling utilities. In particular it
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allows one to perform audio resampling, audio channel layout rematrixing,
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and convert audio format and packing layout.
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=head1 RESAMPLER OPTIONS
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The audio resampler supports the following named options.
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Options may be set by specifying -I<option> I<value> in the
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FFmpeg tools, I<option>=I<value> for the aresample filter,
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by setting the value explicitly in the
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C<SwrContext> options or using the F<libavutil/opt.h> API for
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programmatic use.
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=over 4
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=item B<ich, in_channel_count>
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Set the number of input channels. Default value is 0. Setting this
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value is not mandatory if the corresponding channel layout
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B<in_channel_layout> is set.
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=item B<och, out_channel_count>
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Set the number of output channels. Default value is 0. Setting this
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value is not mandatory if the corresponding channel layout
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B<out_channel_layout> is set.
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=item B<uch, used_channel_count>
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Set the number of used input channels. Default value is 0. This option is
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only used for special remapping.
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=item B<isr, in_sample_rate>
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Set the input sample rate. Default value is 0.
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=item B<osr, out_sample_rate>
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Set the output sample rate. Default value is 0.
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=item B<isf, in_sample_fmt>
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Specify the input sample format. It is set by default to C<none>.
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=item B<osf, out_sample_fmt>
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Specify the output sample format. It is set by default to C<none>.
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=item B<tsf, internal_sample_fmt>
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Set the internal sample format. Default value is C<none>.
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This will automatically be chosen when it is not explicitly set.
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=item B<icl, in_channel_layout>
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=item B<ocl, out_channel_layout>
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Set the input/output channel layout.
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See B<the Channel Layout section in the ffmpeg-utils(1) manual>
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for the required syntax.
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=item B<clev, center_mix_level>
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Set the center mix level. It is a value expressed in deciBel, and must be
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in the interval [-32,32].
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=item B<slev, surround_mix_level>
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Set the surround mix level. It is a value expressed in deciBel, and must
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be in the interval [-32,32].
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=item B<lfe_mix_level>
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Set LFE mix into non LFE level. It is used when there is a LFE input but no
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LFE output. It is a value expressed in deciBel, and must
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be in the interval [-32,32].
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=item B<rmvol, rematrix_volume>
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Set rematrix volume. Default value is 1.0.
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=item B<rematrix_maxval>
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Set maximum output value for rematrixing.
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This can be used to prevent clipping vs. preventing volumn reduction
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A value of 1.0 prevents cliping.
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=item B<flags, swr_flags>
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Set flags used by the converter. Default value is 0.
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It supports the following individual flags:
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=over 4
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=item B<res>
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force resampling, this flag forces resampling to be used even when the
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input and output sample rates match.
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=back
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=item B<dither_scale>
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Set the dither scale. Default value is 1.
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=item B<dither_method>
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Set dither method. Default value is 0.
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Supported values:
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=over 4
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=item B<rectangular>
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select rectangular dither
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=item B<triangular>
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select triangular dither
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=item B<triangular_hp>
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select triangular dither with high pass
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=item B<lipshitz>
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select lipshitz noise shaping dither
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=item B<shibata>
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select shibata noise shaping dither
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=item B<low_shibata>
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select low shibata noise shaping dither
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=item B<high_shibata>
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select high shibata noise shaping dither
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=item B<f_weighted>
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select f-weighted noise shaping dither
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=item B<modified_e_weighted>
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select modified-e-weighted noise shaping dither
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=item B<improved_e_weighted>
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select improved-e-weighted noise shaping dither
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=back
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=item B<resampler>
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Set resampling engine. Default value is swr.
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Supported values:
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=over 4
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=item B<swr>
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select the native SW Resampler; filter options precision and cheby are not
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applicable in this case.
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=item B<soxr>
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select the SoX Resampler (where available); compensation, and filter options
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filter_size, phase_shift, filter_type & kaiser_beta, are not applicable in this
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case.
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=back
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=item B<filter_size>
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For swr only, set resampling filter size, default value is 32.
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=item B<phase_shift>
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For swr only, set resampling phase shift, default value is 10, and must be in
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the interval [0,30].
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=item B<linear_interp>
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Use Linear Interpolation if set to 1, default value is 0.
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=item B<cutoff>
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Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must be a float
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value between 0 and 1. Default value is 0.97 with swr, and 0.91 with soxr
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(which, with a sample-rate of 44100, preserves the entire audio band to 20kHz).
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=item B<precision>
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For soxr only, the precision in bits to which the resampled signal will be
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calculated. The default value of 20 (which, with suitable dithering, is
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appropriate for a destination bit-depth of 16) gives SoX's 'High Quality'; a
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value of 28 gives SoX's 'Very High Quality'.
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=item B<cheby>
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For soxr only, selects passband rolloff none (Chebyshev) & higher-precision
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approximation for 'irrational' ratios. Default value is 0.
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=item B<async>
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For swr only, simple 1 parameter audio sync to timestamps using stretching,
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squeezing, filling and trimming. Setting this to 1 will enable filling and
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trimming, larger values represent the maximum amount in samples that the data
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may be stretched or squeezed for each second.
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Default value is 0, thus no compensation is applied to make the samples match
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the audio timestamps.
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=item B<first_pts>
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For swr only, assume the first pts should be this value. The time unit is 1 / sample rate.
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This allows for padding/trimming at the start of stream. By default, no
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assumption is made about the first frame's expected pts, so no padding or
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trimming is done. For example, this could be set to 0 to pad the beginning with
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silence if an audio stream starts after the video stream or to trim any samples
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with a negative pts due to encoder delay.
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=item B<min_comp>
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For swr only, set the minimum difference between timestamps and audio data (in
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seconds) to trigger stretching/squeezing/filling or trimming of the
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data to make it match the timestamps. The default is that
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stretching/squeezing/filling and trimming is disabled
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(B<min_comp> = C<FLT_MAX>).
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=item B<min_hard_comp>
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For swr only, set the minimum difference between timestamps and audio data (in
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seconds) to trigger adding/dropping samples to make it match the
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timestamps. This option effectively is a threshold to select between
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hard (trim/fill) and soft (squeeze/stretch) compensation. Note that
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all compensation is by default disabled through B<min_comp>.
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The default is 0.1.
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=item B<comp_duration>
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For swr only, set duration (in seconds) over which data is stretched/squeezed
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to make it match the timestamps. Must be a non-negative double float value,
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default value is 1.0.
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=item B<max_soft_comp>
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For swr only, set maximum factor by which data is stretched/squeezed to make it
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match the timestamps. Must be a non-negative double float value, default value
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is 0.
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=item B<matrix_encoding>
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Select matrixed stereo encoding.
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It accepts the following values:
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=over 4
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=item B<none>
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select none
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=item B<dolby>
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select Dolby
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=item B<dplii>
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select Dolby Pro Logic II
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=back
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Default value is C<none>.
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=item B<filter_type>
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For swr only, select resampling filter type. This only affects resampling
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operations.
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It accepts the following values:
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=over 4
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=item B<cubic>
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select cubic
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=item B<blackman_nuttall>
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select Blackman Nuttall Windowed Sinc
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=item B<kaiser>
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select Kaiser Windowed Sinc
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=back
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=item B<kaiser_beta>
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For swr only, set Kaiser Window Beta value. Must be an integer in the
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interval [2,16], default value is 9.
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=item B<output_sample_bits>
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For swr only, set number of used output sample bits for dithering. Must be an integer in the
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interval [0,64], default value is 0, which means it's not used.
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=back
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=head1 SEE ALSO
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ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libswresample(3)
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=head1 AUTHORS
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The FFmpeg developers.
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For details about the authorship, see the Git history of the project
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(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
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B<git log> in the FFmpeg source directory, or browsing the
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online repository at E<lt>B<http://source.ffmpeg.org>E<gt>.
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Maintainers for the specific components are listed in the file
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F<MAINTAINERS> in the source code tree.
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