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diff --git a/doc/encoders.texi b/doc/encoders.texi index cab98fb0bd..2f347f4fb1 100644 --- a/doc/encoders.texi +++ b/doc/encoders.texi @@ -17,4 +17,340 @@ with the options @code{--enable-encoder=@var{ENCODER}} / The option @code{-codecs} of the ff* tools will display the list of enabled encoders. +A description of some of the currently available encoders follows. + +@section Audio Encoders + +@subsection ac3 and ac3_fixed + +AC-3 audio encoders. + +These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as +the undocumented RealAudio 3 (a.k.a. dnet). + +The @var{ac3} encoder uses floating-point math, while the @var{ac3_fixed} +encoder only uses fixed-point integer math. This does not mean that one is +always faster, just that one or the other may be better suited to a +particular system. The floating-point encoder will generally produce better +quality audio for a given bitrate. The @var{ac3_fixed} encoder is not the +default codec for any of the output formats, so it must be specified explicitly +using the option @code{-acodec ac3_fixed} in order to use it. + +@subheading AC-3 Metadata + +The AC-3 metadata options are used to set parameters that describe the audio, +but in most cases do not affect the audio encoding itself. Some of the options +do directly affect or influence the decoding and playback of the resulting +bitstream, while others are just for informational purposes. A few of the +options will add bits to the output stream that could otherwise be used for +audio data, and will thus affect the quality of the output. Those will be +indicated accordingly with a note in the option list below. + +These parameters are described in detail in several publicly-available +documents. +@itemize +@item @uref{http://www.atsc.org/cms/standards/a_52-2010.pdf,A/52:2010 - Digital Audio Compression (AC-3) (E-AC-3) Standard} +@item @uref{http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf,A/54 - Guide to the Use of the ATSC Digital Television Standard} +@item @uref{http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/18_Metadata.Guide.pdf,Dolby Metadata Guide} +@item @uref{http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/46_DDEncodingGuidelines.pdf,Dolby Digital Professional Encoding Guidelines} +@end itemize + +@subsubheading Metadata Control Options + +@table @option + +@item -per_frame_metadata @var{boolean} +Allow Per-Frame Metadata. Specifies if the encoder should check for changing +metadata for each frame. +@table @option +@item 0 +The metadata values set at initialization will be used for every frame in the +stream. (default) +@item 1 +Metadata values can be changed before encoding each frame. +@end table + +@end table + +@subsubheading Downmix Levels + +@table @option + +@item -center_mixlev @var{level} +Center Mix Level. The amount of gain the decoder should apply to the center +channel when downmixing to stereo. This field will only be written to the +bitstream if a center channel is present. The value is specified as a scale +factor. There are 3 valid values: +@table @option +@item 0.707 +Apply -3dB gain +@item 0.595 +Apply -4.5dB gain (default) +@item 0.500 +Apply -6dB gain +@end table + +@item -surround_mixlev @var{level} +Surround Mix Level. The amount of gain the decoder should apply to the surround +channel(s) when downmixing to stereo. This field will only be written to the +bitstream if one or more surround channels are present. The value is specified +as a scale factor. There are 3 valid values: +@table @option +@item 0.707 +Apply -3dB gain +@item 0.500 +Apply -6dB gain (default) +@item 0.000 +Silence Surround Channel(s) +@end table + +@end table + +@subsubheading Audio Production Information +Audio Production Information is optional information describing the mixing +environment. Either none or both of the fields are written to the bitstream. + +@table @option + +@item -mixing_level @var{number} +Mixing Level. Specifies peak sound pressure level (SPL) in the production +environment when the mix was mastered. Valid values are 80 to 111, or -1 for +unknown or not indicated. The default value is -1, but that value cannot be +used if the Audio Production Information is written to the bitstream. Therefore, +if the @code{room_type} option is not the default value, the @code{mixing_level} +option must not be -1. + +@item -room_type @var{type} +Room Type. Describes the equalization used during the final mixing session at +the studio or on the dubbing stage. A large room is a dubbing stage with the +industry standard X-curve equalization; a small room has flat equalization. +This field will not be written to the bitstream if both the @code{mixing_level} +option and the @code{room_type} option have the default values. +@table @option +@item 0 +@itemx notindicated +Not Indicated (default) +@item 1 +@itemx large +Large Room +@item 2 +@itemx small +Small Room +@end table + +@end table + +@subsubheading Other Metadata Options + +@table @option + +@item -copyright @var{boolean} +Copyright Indicator. Specifies whether a copyright exists for this audio. +@table @option +@item 0 +@itemx off +No Copyright Exists (default) +@item 1 +@itemx on +Copyright Exists +@end table + +@item -dialnorm @var{value} +Dialogue Normalization. Indicates how far the average dialogue level of the +program is below digital 100% full scale (0 dBFS). This parameter determines a +level shift during audio reproduction that sets the average volume of the +dialogue to a preset level. The goal is to match volume level between program +sources. A value of -31dB will result in no volume level change, relative to +the source volume, during audio reproduction. Valid values are whole numbers in +the range -31 to -1, with -31 being the default. + +@item -dsur_mode @var{mode} +Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround +(Pro Logic). This field will only be written to the bitstream if the audio +stream is stereo. Using this option does @b{NOT} mean the encoder will actually +apply Dolby Surround processing. +@table @option +@item 0 +@itemx notindicated +Not Indicated (default) +@item 1 +@itemx off +Not Dolby Surround Encoded +@item 2 +@itemx on +Dolby Surround Encoded +@end table + +@item -original @var{boolean} +Original Bit Stream Indicator. Specifies whether this audio is from the +original source and not a copy. +@table @option +@item 0 +@itemx off +Not Original Source +@item 1 +@itemx on +Original Source (default) +@end table + +@end table + +@subsubheading Extended Bitstream Information +The extended bitstream options are part of the Alternate Bit Stream Syntax as +specified in Annex D of the A/52:2010 standard. It is grouped into 2 parts. +If any one parameter in a group is specified, all values in that group will be +written to the bitstream. Default values are used for those that are written +but have not been specified. If the mixing levels are written, the decoder +will use these values instead of the ones specified in the @code{center_mixlev} +and @code{surround_mixlev} options if it supports the Alternate Bit Stream +Syntax. + +@subsubheading Extended Bitstream Information - Part 1 + +@table @option + +@item -dmix_mode @var{mode} +Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt +(Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode. +@table @option +@item 0 +@itemx notindicated +Not Indicated (default) +@item 1 +@itemx ltrt +Lt/Rt Downmix Preferred +@item 2 +@itemx loro +Lo/Ro Downmix Preferred +@end table + +@item -ltrt_cmixlev @var{level} +Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the +center channel when downmixing to stereo in Lt/Rt mode. +@table @option +@item 1.414 +Apply +3dB gain +@item 1.189 +Apply +1.5dB gain +@item 1.000 +Apply 0dB gain +@item 0.841 +Apply -1.5dB gain +@item 0.707 +Apply -3.0dB gain +@item 0.595 +Apply -4.5dB gain (default) +@item 0.500 +Apply -6.0dB gain +@item 0.000 +Silence Center Channel +@end table + +@item -ltrt_surmixlev @var{level} +Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the +surround channel(s) when downmixing to stereo in Lt/Rt mode. +@table @option +@item 0.841 +Apply -1.5dB gain +@item 0.707 +Apply -3.0dB gain +@item 0.595 +Apply -4.5dB gain +@item 0.500 +Apply -6.0dB gain (default) +@item 0.000 +Silence Surround Channel(s) +@end table + +@item -loro_cmixlev @var{level} +Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the +center channel when downmixing to stereo in Lo/Ro mode. +@table @option +@item 1.414 +Apply +3dB gain +@item 1.189 +Apply +1.5dB gain +@item 1.000 +Apply 0dB gain +@item 0.841 +Apply -1.5dB gain +@item 0.707 +Apply -3.0dB gain +@item 0.595 +Apply -4.5dB gain (default) +@item 0.500 +Apply -6.0dB gain +@item 0.000 +Silence Center Channel +@end table + +@item -loro_surmixlev @var{level} +Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the +surround channel(s) when downmixing to stereo in Lo/Ro mode. +@table @option +@item 0.841 +Apply -1.5dB gain +@item 0.707 +Apply -3.0dB gain +@item 0.595 +Apply -4.5dB gain +@item 0.500 +Apply -6.0dB gain (default) +@item 0.000 +Silence Surround Channel(s) +@end table + +@end table + +@subsubheading Extended Bitstream Information - Part 2 + +@table @option + +@item -dsurex_mode @var{mode} +Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX +(7.1 matrixed to 5.1). Using this option does @b{NOT} mean the encoder will actually +apply Dolby Surround EX processing. +@table @option +@item 0 +@itemx notindicated +Not Indicated (default) +@item 1 +@itemx on +Dolby Surround EX On +@item 2 +@itemx off +Dolby Surround EX Off +@end table + +@item -dheadphone_mode @var{mode} +Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone +encoding (multi-channel matrixed to 2.0 for use with headphones). Using this +option does @b{NOT} mean the encoder will actually apply Dolby Headphone +processing. +@table @option +@item 0 +@itemx notindicated +Not Indicated (default) +@item 1 +@itemx on +Dolby Headphone On +@item 2 +@itemx off +Dolby Headphone Off +@end table + +@item -ad_conv_type @var{type} +A/D Converter Type. Indicates whether the audio has passed through HDCD A/D +conversion. +@table @option +@item 0 +@itemx standard +Standard A/D Converter (default) +@item 1 +@itemx hdcd +HDCD A/D Converter +@end table + +@end table + @c man end ENCODERS |