mirror of https://git.ffmpeg.org/ffmpeg.git
618 lines
18 KiB
Plaintext
618 lines
18 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 av1
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AOMedia Video 1 (AV1) decoder.
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@subsection Options
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@table @option
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@item operating_point
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Select an operating point of a scalable AV1 bitstream (0 - 31). Default is 0.
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@end table
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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 libdav1d
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dav1d AV1 decoder.
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libdav1d allows libavcodec to decode the AOMedia Video 1 (AV1) codec.
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Requires the presence of the libdav1d headers and library during configuration.
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You need to explicitly configure the build with @code{--enable-libdav1d}.
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@subsection Options
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The following options are supported by the libdav1d wrapper.
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@table @option
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@item framethreads
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Set amount of frame threads to use during decoding. The default value is 0 (autodetect).
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This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the
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option @code{max_frame_delay} and the global option @code{threads} instead.
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@item tilethreads
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Set amount of tile threads to use during decoding. The default value is 0 (autodetect).
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This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the
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global option @code{threads} instead.
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@item max_frame_delay
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Set max amount of frames the decoder may buffer internally. The default value is 0
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(autodetect).
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@item filmgrain
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Apply film grain to the decoded video if present in the bitstream. Defaults to the
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internal default of the library.
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This option is deprecated and will be removed in the future. See the global option
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@code{export_side_data} to export Film Grain parameters instead of applying it.
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@item oppoint
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Select an operating point of a scalable AV1 bitstream (0 - 31). Defaults to the
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internal default of the library.
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@item alllayers
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Output all spatial layers of a scalable AV1 bitstream. The default value is false.
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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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@section libuavs3d
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AVS3-P2/IEEE1857.10 video decoder.
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libuavs3d allows libavcodec to decode AVS3 streams.
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Requires the presence of the libuavs3d headers and library during configuration.
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You need to explicitly configure the build with @code{--enable-libuavs3d}.
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@subsection Options
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The following option is supported by the libuavs3d wrapper.
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@table @option
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@item frame_threads
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Set amount of frame threads to use during decoding. The default value is 0 (autodetect).
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@end table
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@section QSV Decoders
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The family of Intel QuickSync Video decoders (VC1, MPEG-2, H.264, HEVC,
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JPEG/MJPEG, VP8, VP9, AV1).
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@subsection Common Options
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The following options are supported by all qsv decoders.
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@table @option
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@item @var{async_depth}
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Internal parallelization depth, the higher the value the higher the latency.
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@item @var{gpu_copy}
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A GPU-accelerated copy between video and system memory
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@table @samp
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@item default
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@item on
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@item off
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@end table
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@end table
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@subsection HEVC Options
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Extra options for hevc_qsv.
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@table @option
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@item @var{load_plugin}
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A user plugin to load in an internal session
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@table @samp
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@item none
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@item hevc_sw
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@item hevc_hw
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@end table
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@item @var{load_plugins}
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A :-separate list of hexadecimal plugin UIDs to load in an internal session
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@end table
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@section v210
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Uncompressed 4:2:2 10-bit decoder.
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@subsection Options
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@table @option
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@item custom_stride
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Set the line size of the v210 data in bytes. The default value is 0
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(autodetect). You can use the special -1 value for a strideless v210 as seen in
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BOXX files.
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@end table
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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. The default value is 1.
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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 libaribcaption
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Yet another ARIB STD-B24 caption decoder using external @dfn{libaribcaption}
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library.
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Implements profiles A and C of the Japanse ARIB STD-B24 standard,
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Brazilian ABNT NBR 15606-1, and Philippines version of ISDB-T.
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Requires the presence of the libaribcaption headers and library
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(@url{https://github.com/xqq/libaribcaption}) during configuration.
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You need to explicitly configure the build with @code{--enable-libaribcaption}.
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If both @dfn{libaribb24} and @dfn{libaribcaption} are enabled, @dfn{libaribcaption}
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decoder precedes.
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@subsection libaribcaption Decoder Options
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@table @option
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@item -sub_type @var{subtitle_type}
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Specifies the format of the decoded subtitles.
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@table @samp
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@item bitmap
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Graphical image.
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@item ass
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ASS formatted text.
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@item text
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Simple text based output without formatting.
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@end table
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The default is @dfn{ass} as same as @dfn{libaribb24} decoder.
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Some present players (e.g., @dfn{mpv}) expect ASS format for ARIB caption.
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@item -caption_encoding @var{encoding_scheme}
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Specifies the encoding scheme of input subtitle text.
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@table @samp
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@item auto
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Automatically detect text encoding.
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@item jis
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8bit-char JIS encoding defined in ARIB STD B24.
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This encoding used in Japan for ISDB captions.
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@item utf8
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UTF-8 encoding defined in ARIB STD B24.
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This encoding is used in Philippines for ISDB-T captions.
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@item latin
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Latin character encoding defined in ABNT NBR 15606-1.
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This encoding is used in South America for SBTVD / ISDB-Tb captions.
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@end table
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The default is @dfn{ass} as same as @dfn{libaribb24} decoder.
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Some present players (e.g., @dfn{mpv}) expect ASS format for ARIB caption.
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@item -font @var{font_name[,font_name2,...]}
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Specify comma-separated list of font family names to be used for @dfn{bitmap}
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or @dfn{ass} type subtitle rendering.
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Only first font name is used for @dfn{ass} type subtitle.
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If not specified, use internaly defined default font family.
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@item -ass_single_rect @var{boolean}
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ARIB STD-B24 specifies that some captions may be displayed at different
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positions at a time (multi-rectangle subtitle).
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Since some players (e.g., old @dfn{mpv}) can't handle multiple ASS rectangles
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in a single AVSubtitle, or multiple ASS rectangles of indeterminate duration
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with the same start timestamp, this option can change the behavior so that
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all the texts are displayed in a single ASS rectangle.
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The default is @var{false}.
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If your player cannot handle AVSubtitles with multiple ASS rectangles properly,
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set this option to @var{true} or define @env{ASS_SINGLE_RECT=1} to change
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default behavior at compilation.
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@item -replace_fullwidth_ascii @var{boolean}
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Specify whether to replace MSZ (Middle Size, half width) fullwidth
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alphanumerics with halfwidth alphanumerics.
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The default is @var{true}.
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@item -force_outline_text @var{boolean}
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Specify whether always render outline text for all characters regardless of
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the indication by charactor style.
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The default is @var{false}.
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@item -outline_width @var{number} (0.0 - 3.0)
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Specify width for outline text, in dots (relative).
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The default is @var{1.5}.
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@item -ignore_background @var{boolean}
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Specify whether to ignore background color rendering.
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The default is @var{false}.
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@item -ignore_ruby @var{boolean}
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Specify whether to ignore rendering for ruby-like (furigana) characters.
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The default is @var{false}.
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@item -replace_drcs @var{boolean}
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Specify whether to render replaced DRCS characters as Unicode characters.
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The default is @var{true}.
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@item -canvas_size @var{image_size}
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Specify the resolution of the canvas to render subtitles to; usually, this
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should be frame size of input video.
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This only applies when @code{-subtitle_type} is set to @var{bitmap}.
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The libaribcaption decoder assumes input frame size for bitmap rendering as below:
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@enumerate
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@item
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PROFILE_A : 1440 x 1080 with SAR (PAR) 4:3
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@item
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PROFILE_C : 320 x 180 with SAR (PAR) 1:1
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@end enumerate
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If actual frame size of input video does not match above assumption,
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the rendered captions may be distorted.
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To make the captions undistorted, add @code{-canvas_size} option to specify
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actual input video size.
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Note that the @code{-canvas_size} option is not required for video with
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different size but same aspect ratio.
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In such cases, the caption will be stretched or shrunk to actual video size
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if @code{-canvas_size} option is not specified.
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If @code{-canvas_size} option is specified with different size,
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the caption will be stretched or shrunk as specified size with calculated SAR.
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@end table
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@subsection libaribcaption decoder usage examples
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Display MPEG-TS file with ARIB subtitle by @code{ffplay} tool:
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@example
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ffplay -sub_type bitmap MPEG.TS
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@end example
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Display MPEG-TS file with input frame size 1920x1080 by @code{ffplay} tool:
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@example
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ffplay -sub_type bitmap -canvas_size 1920x1080 MPEG.TS
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@end example
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Embed ARIB subtitle in transcoded video:
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@example
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ffmpeg -sub_type bitmap -i src.m2t -filter_complex "[0:v][0:s]overlay" -vcodec h264 dest.mp4
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@end example
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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 -2
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Compute clut once if no matching CLUT is in the stream.
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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 commas, 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,
|
|
or @code{subtitle} to match all subtitle pages.
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|
Default value is *.
|
|
@item txt_default_region
|
|
Set default character set used for decoding, a value between 0 and 87 (see
|
|
ETS 300 706, Section 15, Table 32). Default value is -1, which does not
|
|
override the libzvbi default. This option is needed for some legacy level 1.0
|
|
transmissions which cannot signal the proper charset.
|
|
@item txt_chop_top
|
|
Discards the top teletext line. Default value is 1.
|
|
@item txt_format
|
|
Specifies the format of the decoded subtitles.
|
|
@table @option
|
|
@item bitmap
|
|
The default format, you should use this for teletext pages, because certain
|
|
graphics and colors cannot be expressed in simple text or even ASS.
|
|
@item text
|
|
Simple text based output without formatting.
|
|
@item ass
|
|
Formatted ASS output, subtitle pages and teletext pages are returned in
|
|
different styles, subtitle pages are stripped down to text, but an effort is
|
|
made to keep the text alignment and the formatting.
|
|
@end table
|
|
@item txt_left
|
|
X offset of generated bitmaps, default is 0.
|
|
@item txt_top
|
|
Y offset of generated bitmaps, default is 0.
|
|
@item txt_chop_spaces
|
|
Chops leading and trailing spaces and removes empty lines from the generated
|
|
text. This option is useful for teletext based subtitles where empty spaces may
|
|
be present at the start or at the end of the lines or empty lines may be
|
|
present between the subtitle lines because of double-sized teletext characters.
|
|
Default value is 1.
|
|
@item txt_duration
|
|
Sets the display duration of the decoded teletext pages or subtitles in
|
|
milliseconds. Default value is -1 which means infinity or until the next
|
|
subtitle event comes.
|
|
@item txt_transparent
|
|
Force transparent background of the generated teletext bitmaps. Default value
|
|
is 0 which means an opaque background.
|
|
@item txt_opacity
|
|
Sets the opacity (0-255) of the teletext background. If
|
|
@option{txt_transparent} is not set, it only affects characters between a start
|
|
box and an end box, typically subtitles. Default value is 0 if
|
|
@option{txt_transparent} is set, 255 otherwise.
|
|
|
|
@end table
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|
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@c man end SUBTILES DECODERS
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