avcodec: add minimal teletext subtitle decoder

Based largely on VLC's modules/codec/telx.c. Processes only teletext pages marked as subtitles, so depending on the stream it might not produce any output. Subtitles are rendered directly to ASS, with support for background colors and a best-effort at screen positioning. The ASS packets are emitted in real time (similar to ccaption_dec's real_time option), with -1 durations. The decoder expects that the player will remove all existing subtitles whenever a new packet arrives. The teletext clear command is implemented using an empty subtitle, which removes existing subtitles but does not render anything new.
tmm1 · Apr 25, 2018 · ba1cabeda654a72b7e6e52c82bc7b16abad55a45 · ba1cabe
1 parent d06b01f
commit ba1cabeda654a72b7e6e52c82bc7b16abad55a45
Unified Split

Showing with 524 additions and 0 deletions.

+1 −0 libavcodec/Makefile

+1 −0 libavcodec/allcodecs.c

+522 −0 libavcodec/teletextsubdec.c
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
@@ -593,6 +593,7 @@ OBJS-$(CONFIG_SVQ1_DECODER)            += svq1dec.o svq1.o svq13.o h263data.o
 OBJS-$(CONFIG_SVQ1_ENCODER)            += svq1enc.o svq1.o  h263data.o  \
                                           h263.o ituh263enc.o
 OBJS-$(CONFIG_SVQ3_DECODER)            += svq3.o svq13.o mpegutils.o h264data.o
+OBJS-$(CONFIG_TELETEXTSUB_DECODER)     += teletextsubdec.o ass.o
 OBJS-$(CONFIG_TEXT_DECODER)            += textdec.o ass.o
 OBJS-$(CONFIG_TEXT_ENCODER)            += srtenc.o ass_split.o
 OBJS-$(CONFIG_TAK_DECODER)             += takdec.o tak.o takdsp.o

diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
@@ -634,6 +634,7 @@ extern AVCodec ff_subrip_encoder;
 extern AVCodec ff_subrip_decoder;
 extern AVCodec ff_subviewer_decoder;
 extern AVCodec ff_subviewer1_decoder;
+extern AVCodec ff_teletextsub_decoder;
 extern AVCodec ff_text_encoder;
 extern AVCodec ff_text_decoder;
 extern AVCodec ff_vplayer_decoder;