mirror of
https://gitee.com/openharmony/third_party_ffmpeg
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100bfac6d6
* Outputs ASS lines with basic coloring and font scaling for each
given region.
* Sets the default style to the resolution of the subtitle plane
(for example, 960x540 / 36pt font for profile A).
* Has options to:
* Disable ruby text (which is coded as regions which have
half-height text in libaribb24).
Enabled by default as without positioning ruby text only
confuses as it is usually coded in the beginning of the decoded
subtitle line.
* Set the working directory, in which libaribb24 will read
configuration as well as into which it may save broadcast extra
symbols as PNG.
Unset by default.
The unconventional library check can be explained by the library's
current master branch being licensed as LGPLv3, but at the time of
writing the latest official release is still licensed under GPLv3.
Thus, one either has to wait for the following release, or enable
GPLv3.
327 lines
9.5 KiB
Plaintext
327 lines
9.5 KiB
Plaintext
@chapter Decoders
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@c man begin DECODERS
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Decoders are configured elements in FFmpeg which allow the decoding of
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multimedia streams.
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When you configure your FFmpeg build, all the supported native decoders
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are enabled by default. Decoders requiring an external library must be enabled
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manually via the corresponding @code{--enable-lib} option. You can list all
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available decoders using the configure option @code{--list-decoders}.
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You can disable all the decoders with the configure option
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@code{--disable-decoders} and selectively enable / disable single decoders
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with the options @code{--enable-decoder=@var{DECODER}} /
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@code{--disable-decoder=@var{DECODER}}.
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The option @code{-decoders} of the ff* tools will display the list of
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enabled decoders.
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@c man end DECODERS
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@chapter Video Decoders
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@c man begin VIDEO DECODERS
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A description of some of the currently available video decoders
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follows.
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@section rawvideo
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Raw video decoder.
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This decoder decodes rawvideo streams.
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@subsection Options
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@table @option
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@item top @var{top_field_first}
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Specify the assumed field type of the input video.
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@table @option
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@item -1
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the video is assumed to be progressive (default)
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@item 0
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bottom-field-first is assumed
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@item 1
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top-field-first is assumed
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@end table
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@end table
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@section libdavs2
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AVS2-P2/IEEE1857.4 video decoder wrapper.
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This decoder allows libavcodec to decode AVS2 streams with davs2 library.
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@c man end VIDEO DECODERS
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@chapter Audio Decoders
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@c man begin AUDIO DECODERS
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A description of some of the currently available audio decoders
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follows.
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@section ac3
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AC-3 audio decoder.
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This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as
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the undocumented RealAudio 3 (a.k.a. dnet).
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@subsection AC-3 Decoder Options
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@table @option
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@item -drc_scale @var{value}
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Dynamic Range Scale Factor. The factor to apply to dynamic range values
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from the AC-3 stream. This factor is applied exponentially.
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There are 3 notable scale factor ranges:
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@table @option
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@item drc_scale == 0
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DRC disabled. Produces full range audio.
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@item 0 < drc_scale <= 1
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DRC enabled. Applies a fraction of the stream DRC value.
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Audio reproduction is between full range and full compression.
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@item drc_scale > 1
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DRC enabled. Applies drc_scale asymmetrically.
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Loud sounds are fully compressed. Soft sounds are enhanced.
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@end table
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@end table
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@section flac
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FLAC audio decoder.
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This decoder aims to implement the complete FLAC specification from Xiph.
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@subsection FLAC Decoder options
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@table @option
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@item -use_buggy_lpc
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The lavc FLAC encoder used to produce buggy streams with high lpc values
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(like the default value). This option makes it possible to decode such streams
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correctly by using lavc's old buggy lpc logic for decoding.
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@end table
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@section ffwavesynth
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Internal wave synthesizer.
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This decoder generates wave patterns according to predefined sequences. Its
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use is purely internal and the format of the data it accepts is not publicly
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documented.
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@section libcelt
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libcelt decoder wrapper.
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libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.
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Requires the presence of the libcelt headers and library during configuration.
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You need to explicitly configure the build with @code{--enable-libcelt}.
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@section libgsm
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libgsm decoder wrapper.
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libgsm allows libavcodec to decode the GSM full rate audio codec. Requires
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the presence of the libgsm headers and library during configuration. You need
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to explicitly configure the build with @code{--enable-libgsm}.
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This decoder supports both the ordinary GSM and the Microsoft variant.
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@section libilbc
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libilbc decoder wrapper.
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libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)
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audio codec. Requires the presence of the libilbc headers and library during
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configuration. You need to explicitly configure the build with
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@code{--enable-libilbc}.
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@subsection Options
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The following option is supported by the libilbc wrapper.
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@table @option
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@item enhance
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Enable the enhancement of the decoded audio when set to 1. The default
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value is 0 (disabled).
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@end table
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@section libopencore-amrnb
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libopencore-amrnb decoder wrapper.
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libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
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Narrowband audio codec. Using it requires the presence of the
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libopencore-amrnb headers and library during configuration. You need to
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explicitly configure the build with @code{--enable-libopencore-amrnb}.
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An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB
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without this library.
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@section libopencore-amrwb
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libopencore-amrwb decoder wrapper.
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libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
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Wideband audio codec. Using it requires the presence of the
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libopencore-amrwb headers and library during configuration. You need to
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explicitly configure the build with @code{--enable-libopencore-amrwb}.
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An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB
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without this library.
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@section libopus
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libopus decoder wrapper.
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libopus allows libavcodec to decode the Opus Interactive Audio Codec.
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Requires the presence of the libopus headers and library during
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configuration. You need to explicitly configure the build with
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@code{--enable-libopus}.
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An FFmpeg native decoder for Opus exists, so users can decode Opus
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without this library.
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@c man end AUDIO DECODERS
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@chapter Subtitles Decoders
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@c man begin SUBTILES DECODERS
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@section libaribb24
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ARIB STD-B24 caption decoder.
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Implements profiles A and C of the ARIB STD-B24 standard.
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@subsection libaribb24 Decoder Options
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@table @option
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@item -aribb24-base-path @var{path}
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Sets the base path for the libaribb24 library. This is utilized for reading of
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configuration files (for custom unicode conversions), and for dumping of
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non-text symbols as images under that location.
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Unset by default.
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@item -aribb24-skip-ruby-text @var{boolean}
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Tells the decoder wrapper to skip text blocks that contain half-height ruby
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text.
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Enabled by default.
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@end table
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@section dvbsub
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@subsection Options
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@table @option
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@item compute_clut
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@table @option
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@item -1
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Compute clut if no matching CLUT is in the stream.
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@item 0
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Never compute CLUT
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@item 1
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Always compute CLUT and override the one provided in the stream.
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@end table
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@item dvb_substream
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Selects the dvb substream, or all substreams if -1 which is default.
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@end table
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@section dvdsub
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This codec decodes the bitmap subtitles used in DVDs; the same subtitles can
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also be found in VobSub file pairs and in some Matroska files.
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@subsection Options
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@table @option
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@item palette
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Specify the global palette used by the bitmaps. When stored in VobSub, the
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palette is normally specified in the index file; in Matroska, the palette is
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stored in the codec extra-data in the same format as in VobSub. In DVDs, the
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palette is stored in the IFO file, and therefore not available when reading
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from dumped VOB files.
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The format for this option is a string containing 16 24-bits hexadecimal
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numbers (without 0x prefix) separated by comas, for example @code{0d00ee,
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ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1,
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7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b}.
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@item ifo_palette
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Specify the IFO file from which the global palette is obtained.
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(experimental)
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@item forced_subs_only
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Only decode subtitle entries marked as forced. Some titles have forced
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and non-forced subtitles in the same track. Setting this flag to @code{1}
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will only keep the forced subtitles. Default value is @code{0}.
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@end table
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@section libzvbi-teletext
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Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
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subtitles. Requires the presence of the libzvbi headers and library during
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configuration. You need to explicitly configure the build with
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@code{--enable-libzvbi}.
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@subsection Options
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@table @option
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@item txt_page
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List of teletext page numbers to decode. Pages that do not match the specified
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list are dropped. You may use the special @code{*} string to match all pages,
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or @code{subtitle} to match all subtitle pages.
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Default value is *.
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@item txt_chop_top
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Discards the top teletext line. Default value is 1.
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@item txt_format
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Specifies the format of the decoded subtitles.
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@table @option
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@item bitmap
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The default format, you should use this for teletext pages, because certain
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graphics and colors cannot be expressed in simple text or even ASS.
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@item text
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Simple text based output without formatting.
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@item ass
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Formatted ASS output, subtitle pages and teletext pages are returned in
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different styles, subtitle pages are stripped down to text, but an effort is
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made to keep the text alignment and the formatting.
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@end table
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@item txt_left
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X offset of generated bitmaps, default is 0.
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@item txt_top
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Y offset of generated bitmaps, default is 0.
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@item txt_chop_spaces
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Chops leading and trailing spaces and removes empty lines from the generated
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text. This option is useful for teletext based subtitles where empty spaces may
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be present at the start or at the end of the lines or empty lines may be
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present between the subtitle lines because of double-sized teletext characters.
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Default value is 1.
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@item txt_duration
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Sets the display duration of the decoded teletext pages or subtitles in
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milliseconds. Default value is -1 which means infinity or until the next
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subtitle event comes.
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@item txt_transparent
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Force transparent background of the generated teletext bitmaps. Default value
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is 0 which means an opaque background.
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@item txt_opacity
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Sets the opacity (0-255) of the teletext background. If
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@option{txt_transparent} is not set, it only affects characters between a start
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box and an end box, typically subtitles. Default value is 0 if
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@option{txt_transparent} is set, 255 otherwise.
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@end table
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@c man end SUBTILES DECODERS
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