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Linshizhi
ffmpeg.wasm-core
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0384e3d5
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0384e3d5
authored
Feb 12, 2016
by
Rostislav Pehlivanov
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doc/encoders: add documentation for the VC-2 encoder
Signed-off-by:
Rostislav Pehlivanov
<
atomnuker@gmail.com
>
parent
13ea7c97
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doc/encoders.texi
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0384e3d5
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@@ -2521,6 +2521,71 @@ encoder use CAVLC instead of CABAC.
@end itemize
@section vc2
SMPTE VC-2 (previously BBC Dirac Pro). This codec was primarily aimed at
professional broadcasting but since it supports yuv420, yuv422 and yuv444 at
8 (limited range or full range), 10 or 12 bits, this makes it suitable for
other tasts which require low overhead and low compression (like screen
recording).
@subsection Options
@table @option
@item b
Sets target video bitrate. Usually that's around 1:6 of the uncompressed
video bitrate (e.g. for 1920x1080 50fps yuv422p10 that's around 400Mbps). Higher
values (close to the uncompressed bitrate) turn on lossless compression mode.
@item field_order
Enables field coding when set (e.g. to tt - top field first) for interlaced
inputs. Should increase compression with interlaced content as it splits the
fields and encodes each separately.
@item wavelet_depth
Sets the total amount of wavelet transforms to apply, between 1 and 5 (default).
Lower values reduce compression and quality. Less capable decoders may not be
able to handle values of @option{wavelet_depth} over 3.
@item wavelet_type
Sets the transform type. Currently only @var{5_3} (LeGall) and @var{9_7}
(Deslauriers-Dubuc)
are implemented, with 9_7 being the one with better compression and thus
is the default.
@item slice_width
@item slice_height
Sets the slice size for each slice. Larger values result in better compression.
For compatibility with other more limited decoders use @option{slice_width} of
32 and @option{slice_height} of 8.
@item tolerance
Sets the undershoot tolerance of the rate control system in percent. This is
to prevent an expensive search from being run.
@item qm
Sets the quantization matrix preset to use by default or when @option{wavelet_depth}
is set to 5
@itemize @minus
@item
@var{default}
Uses the default quantization matrix from the specifications, extended with
values for the fifth level. This provides a good balance between keeping detail
and omitting artifacts.
@item
@var{flat}
Use a completely zeroed out quantization matrix. This increases PSNR but might
reduce perception. Use in bogus benchmarks.
@item
@var{color}
Reduces detail but attempts to preserver color at extremely low bitrates.
@end itemize
@end table
@c man end VIDEO ENCODERS
@chapter Subtitles Encoders
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