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author | Stefano Sabatini <stefasab@gmail.com> | 2013-10-30 15:10:04 +0100 |
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committer | Stefano Sabatini <stefasab@gmail.com> | 2013-11-01 12:51:39 +0100 |
commit | 4fdec65eb3c1123b3a330d2e244a4bae25b116b0 (patch) | |
tree | af34bcbe099424a0a59a978b3098db9f19f64340 | |
parent | a2bfee36b70bc9a5dd0a5a1cef36ca32bc1fba07 (diff) | |
download | ffmpeg-4fdec65eb3c1123b3a330d2e244a4bae25b116b0.tar.gz |
doc/encoders: extend/clarify libtheora encoder documentation
-rw-r--r-- | doc/encoders.texi | 53 |
1 files changed, 39 insertions, 14 deletions
diff --git a/doc/encoders.texi b/doc/encoders.texi index 67f2a39278..7825b9a4fa 100644 --- a/doc/encoders.texi +++ b/doc/encoders.texi @@ -902,12 +902,15 @@ follows. @section libtheora -Theora format supported through libtheora. +libtheora Theora encoder wrapper. Requires the presence of the libtheora headers and library during configuration. You need to explicitly configure the build with @code{--enable-libtheora}. +For more informations about the libtheora project see +@url{http://www.theora.org/}. + @subsection Options The following global options are mapped to internal libtheora options @@ -915,11 +918,11 @@ which affect the quality and the bitrate of the encoded stream. @table @option @item b -Set the video bitrate, only works if the @code{qscale} flag in -@option{flags} is not enabled. +Set the video bitrate in bit/s for CBR (Constant Bit Rate) mode. In +case VBR (Variable Bit Rate) mode is enabled this option is ignored. @item flags -Used to enable constant quality mode encoding through the +Used to enable constant quality mode (VBR) encoding through the @option{qscale} flag, and to enable the @code{pass1} and @code{pass2} modes. @@ -927,18 +930,40 @@ modes. Set the GOP size. @item global_quality -Set the global quality in lambda units, only works if the -@code{qscale} flag in @option{flags} is enabled. The value is clipped -in the [0 - 10*@code{FF_QP2LAMBDA}] range, and then multiplied for 6.3 -to get a value in the native libtheora range [0-63]. A higher value -corresponds to a higher quality. - -For example, to set maximum constant quality encoding with -@command{ffmpeg}: +Set the global quality as an integer in lambda units. + +Only relevant when VBR mode is enabled with @code{flags +qscale}. The +value is converted to QP units by dividing it by @code{FF_QP2LAMBDA}, +clipped in the [0 - 10] range, and then multiplied by 6.3 to get a +value in the native libtheora range [0-63]. A higher value corresponds +to a higher quality. + +@item q +Enable VBR mode when set to a non-negative value, and set constant +quality value as a double floating point value in QP units. + +The value is clipped in the [0-10] range, and then multiplied by 6.3 +to get a value in the native libtheora range [0-63]. + +This option is valid only using the @command{ffmpeg} command-line +tool. For library interface users, use @option{global_quality}. +@end table + +@subsection Examples + +@itemize +@item +Set maximum constant quality (VBR) encoding with @command{ffmpeg}: @example -ffmpeg -i INPUT -flags:v qscale -global_quality:v "10*QP2LAMBDA" -codec:v libtheora OUTPUT.ogg +ffmpeg -i INPUT -codec:v libtheora -q:v 10 OUTPUT.ogg @end example -@end table + +@item +Use @command{ffmpeg} to convert a CBR 1000 kbps Theora video stream: +@example +ffmpeg -i INPUT -codec:v libtheora -b:v 1000k OUTPUT.ogg +@end example +@end itemize @section libvpx |