1 \input texinfo @c -*- texinfo -*-
3 @settitle FFmpeg Resampler Documentation
5 @center @titlefont{FFmpeg Resampler Documentation}
13 @c man begin DESCRIPTION
15 The FFmpeg resampler provides an high-level interface to the
16 libswresample library audio resampling utilities. In particular it
17 allows to perform audio resampling, audio channel layout rematrixing,
18 and convert audio format and packing layout.
20 @c man end DESCRIPTION
22 @chapter Resampler Options
23 @c man begin RESAMPLER OPTIONS
25 The audio resampler supports the following named options.
27 Options may be set by specifying -@var{option} @var{value} in the
28 FFmpeg tools, or by setting the value explicitly in the
29 @code{SwrContext} options or using the @file{libavutil/opt.h} API for
34 @item ich, in_channel_count
35 Set the number of input channels. Default value is 0. Setting this
36 value is not mandatory if the corresponding channel layout
37 @option{in_channel_layout} is set.
39 @item och, out_channel_count
40 Set the number of output channels. Default value is 0. Setting this
41 value is not mandatory if the corresponding channel layout
42 @option{out_channel_layout} is set.
44 @item uch, used_channel_count
45 Set the number of used channels. Default value is 0. This option is
46 only used for special remapping.
48 @item isr, in_sample_rate
49 Set the input sample rate. Default value is 0.
51 @item osr, out_sample_rate
52 Set the output sample rate. Default value is 0.
54 @item isf, in_sample_fmt
55 Specify the input sample format. It is set by default to @code{none}.
57 @item osf, out_sample_fmt
58 Specify the output sample format. It is set by default to @code{none}.
60 @item tsf, internal_sample_fmt
61 Set the internal sample format. Default value is @code{none}.
63 @item icl, in_channel_layout
64 Set the input channel layout.
66 @item ocl, out_channel_layout
67 Set the output channel layout.
69 @item clev, center_mix_level
70 Set center mix level. It is a value expressed in deciBel, and must be
71 inclusively included between -32 and +32.
73 @item slev, surround_mix_level
74 Set surround mix level. It is a value expressed in deciBel, and must
75 be inclusively included between -32 and +32.
80 @item rmvol, rematrix_volume
81 Set rematrix volume. Default value is 1.0.
83 @item flags, swr_flags
84 Set flags used by the converter. Default value is 0.
86 It supports the following individual flags:
93 Set the dither scale. Default value is 1.
96 Set dither method. Default value is 0.
101 select rectangular dither
103 select triangular dither
105 select triangular dither with high pass
109 Set resampling filter size, default value is 16.
112 Set resampling phase shift, default value is 10, must be included
116 Use Linear Interpolation if set to 1, default value is 0.
119 Set cutoff frequency ratio. Must be a float value between 0 and 1,
120 default value is 0.8.
123 Set minimum difference between timestamps and audio data (in seconds)
124 below which no timestamp compensation of either kind is applied.
125 Default value is @code{FLT_MAX}.
128 Set minimum difference between timestamps and audio data (in seconds)
129 to trigger padding/trimming the data. Must be a non-negative double,
130 default value is 0.1.
133 Set duration (in seconds) over which data is stretched/squeezed to
134 make it match the timestamps. Must be a non-negative double float
135 value, default value is 1.0.
138 Set maximum factor by which data is stretched/squeezed to make it
139 match the timestamps. Must be a non-negative double float value,
142 @item matrix_encoding
143 Select matrixed stereo encoding.
145 It accepts the following values:
152 select Dolby Pro Logic II
155 Default value is @code{none}.
158 Select resampling filter type. This only affects resampling
161 It accepts the following values:
165 @item blackman_nuttall
166 select Blackman Nuttall Windowed Sinc
168 select Kaiser Windowed Sinc
172 Set Kaiser Window Beta value. Must be an integer included between 2
173 and 16, default value is 9.
177 @c man end RESAMPLER OPTIONS
181 @setfilename ffmpeg-resampler
182 @settitle FFmpeg Resampler
185 ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libswresample(3)
189 See Git history (git://source.ffmpeg.org/ffmpeg)