4 Decoders are configured elements in FFmpeg which allow the decoding of
7 When you configure your FFmpeg build, all the supported native decoders
8 are enabled by default. Decoders requiring an external library must be enabled
9 manually via the corresponding @code{--enable-lib} option. You can list all
10 available decoders using the configure option @code{--list-decoders}.
12 You can disable all the decoders with the configure option
13 @code{--disable-decoders} and selectively enable / disable single decoders
14 with the options @code{--enable-decoder=@var{DECODER}} /
15 @code{--disable-decoder=@var{DECODER}}.
17 The option @code{-decoders} of the ff* tools will display the list of
22 @chapter Video Decoders
23 @c man begin VIDEO DECODERS
25 A description of some of the currently available video decoders
32 Note: the @option{skip_loop_filter} option has effect only at level
39 This decoder decodes rawvideo streams.
44 @item top @var{top_field_first}
45 Specify the assumed field type of the input video.
48 the video is assumed to be progressive (default)
50 bottom-field-first is assumed
52 top-field-first is assumed
57 @c man end VIDEO DECODERS
59 @chapter Audio Decoders
60 @c man begin AUDIO DECODERS
62 A description of some of the currently available audio decoders
69 This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as
70 the undocumented RealAudio 3 (a.k.a. dnet).
72 @subsection AC-3 Decoder Options
76 @item -drc_scale @var{value}
77 Dynamic Range Scale Factor. The factor to apply to dynamic range values
78 from the AC-3 stream. This factor is applied exponentially.
79 There are 3 notable scale factor ranges:
82 DRC disabled. Produces full range audio.
83 @item 0 < drc_scale <= 1
84 DRC enabled. Applies a fraction of the stream DRC value.
85 Audio reproduction is between full range and full compression.
87 DRC enabled. Applies drc_scale asymmetrically.
88 Loud sounds are fully compressed. Soft sounds are enhanced.
97 This decoder aims to implement the complete FLAC specification from Xiph.
99 @subsection FLAC Decoder options
104 The lavc FLAC encoder used to produce buggy streams with high lpc values
105 (like the default value). This option makes it possible to decode such streams
106 correctly by using lavc's old buggy lpc logic for decoding.
112 Internal wave synthetizer.
114 This decoder generates wave patterns according to predefined sequences. Its
115 use is purely internal and the format of the data it accepts is not publicly
120 libcelt decoder wrapper.
122 libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.
123 Requires the presence of the libcelt headers and library during configuration.
124 You need to explicitly configure the build with @code{--enable-libcelt}.
128 libgsm decoder wrapper.
130 libgsm allows libavcodec to decode the GSM full rate audio codec. Requires
131 the presence of the libgsm headers and library during configuration. You need
132 to explicitly configure the build with @code{--enable-libgsm}.
134 This decoder supports both the ordinary GSM and the Microsoft variant.
138 libilbc decoder wrapper.
140 libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)
141 audio codec. Requires the presence of the libilbc headers and library during
142 configuration. You need to explicitly configure the build with
143 @code{--enable-libilbc}.
147 The following option is supported by the libilbc wrapper.
152 Enable the enhancement of the decoded audio when set to 1. The default
153 value is 0 (disabled).
157 @section libopencore-amrnb
159 libopencore-amrnb decoder wrapper.
161 libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
162 Narrowband audio codec. Using it requires the presence of the
163 libopencore-amrnb headers and library during configuration. You need to
164 explicitly configure the build with @code{--enable-libopencore-amrnb}.
166 An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB
167 without this library.
169 @section libopencore-amrwb
171 libopencore-amrwb decoder wrapper.
173 libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
174 Wideband audio codec. Using it requires the presence of the
175 libopencore-amrwb headers and library during configuration. You need to
176 explicitly configure the build with @code{--enable-libopencore-amrwb}.
178 An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB
179 without this library.
183 libopus decoder wrapper.
185 libopus allows libavcodec to decode the Opus Interactive Audio Codec.
186 Requires the presence of the libopus headers and library during
187 configuration. You need to explicitly configure the build with
188 @code{--enable-libopus}.
190 An FFmpeg native decoder for Opus exists, so users can decode Opus
191 without this library.
193 @c man end AUDIO DECODERS
195 @chapter Subtitles Decoders
196 @c man begin SUBTILES DECODERS
206 Compute clut if no matching CLUT is in the stream.
210 Always compute CLUT and override the one provided in the stream.
217 This codec decodes the bitmap subtitles used in DVDs; the same subtitles can
218 also be found in VobSub file pairs and in some Matroska files.
224 Specify the global palette used by the bitmaps. When stored in VobSub, the
225 palette is normally specified in the index file; in Matroska, the palette is
226 stored in the codec extra-data in the same format as in VobSub. In DVDs, the
227 palette is stored in the IFO file, and therefore not available when reading
228 from dumped VOB files.
230 The format for this option is a string containing 16 24-bits hexadecimal
231 numbers (without 0x prefix) separated by comas, for example @code{0d00ee,
232 ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1,
233 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b}.
236 Specify the IFO file from which the global palette is obtained.
239 @item forced_subs_only
240 Only decode subtitle entries marked as forced. Some titles have forced
241 and non-forced subtitles in the same track. Setting this flag to @code{1}
242 will only keep the forced subtitles. Default value is @code{0}.
245 @section libzvbi-teletext
247 Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
248 subtitles. Requires the presence of the libzvbi headers and library during
249 configuration. You need to explicitly configure the build with
250 @code{--enable-libzvbi}.
256 List of teletext page numbers to decode. You may use the special * string to
257 match all pages. Pages that do not match the specified list are dropped.
260 Discards the top teletext line. Default value is 1.
262 Specifies the format of the decoded subtitles. The teletext decoder is capable
263 of decoding the teletext pages to bitmaps or to simple text, you should use
264 "bitmap" for teletext pages, because certain graphics and colors cannot be
265 expressed in simple text. You might use "text" for teletext based subtitles if
266 your application can handle simple text based subtitles. Default value is
269 X offset of generated bitmaps, default is 0.
271 Y offset of generated bitmaps, default is 0.
272 @item txt_chop_spaces
273 Chops leading and trailing spaces and removes empty lines from the generated
274 text. This option is useful for teletext based subtitles where empty spaces may
275 be present at the start or at the end of the lines or empty lines may be
276 present between the subtitle lines because of double-sized teletext charactes.
279 Sets the display duration of the decoded teletext pages or subtitles in
280 miliseconds. Default value is 30000 which is 30 seconds.
281 @item txt_transparent
282 Force transparent background of the generated teletext bitmaps. Default value
283 is 0 which means an opaque (black) background.
286 @c man end SUBTILES DECODERS