libzvbi-teletext


Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext subtitles. Requires the presence of the libzvbi headers and library during configuration. You need to explicitly configure the build with --enable-libzvbi.

'txt_page'

List of teletext page numbers to decode. Pages that do not match the specified list are dropped. You may use the special * string to match all pages, or subtitle to match all subtitle pages. Default value is *.

'txt_chop_top'

Discards the top teletext line. Default value is 1.

'txt_format'

Specifies the format of the decoded subtitles.

'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.

'text'

Simple text based output without formatting.

'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.

'txt_left'

X offset of generated bitmaps, default is 0.

'txt_top'

Y offset of generated bitmaps, default is 0.

'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.

'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.

'txt_transparent'

Force transparent background of the generated teletext bitmaps. Default value is 0 which means an opaque background.

'txt_opacity'

Sets the opacity (0-255) of the teletext background. If 'txt_transparent' is not set, it only affects characters between a start box and an end box, typically subtitles. Default value is 0 if 'txt_transparent' is set, 255 otherwise.

Encoders are configured elements in FFmpeg which allow the encoding of multimedia streams.

When you configure your FFmpeg build, all the supported native encoders are enabled by default. Encoders requiring an external library must be enabled manually via the corresponding --enable-lib option. You can list all available encoders using the configure option --list-encoders.

You can disable all the encoders with the configure option --disable-encoders and selectively enable / disable single encoders with the options --enable-encoder=ENCODER / --disable-encoder=ENCODER.

The option -encoders of the ff* tools will display the list of enabled encoders.

A description of some of the currently available audio encoders follows.