[FFmpeg-devel] [PATCH] lavf/matroska: Handle ASS as ASS instead of SSA

[Clément Bœsch]

On Thu, May 01, 2014 at 01:18:32AM +0400, ValdikSS wrote:
> On 05/01/2014 01:05 AM, Clément Bœsch wrote:
> >On Thu, May 01, 2014 at 12:56:23AM +0400, ValdikSS wrote:
> >>After introducing ASS codec id and renaming (old) ASS to SSA,
> >>Matroska ASS codec tag was mistakenly renamed too, making ASS
> >>subtitles handled as SSA.
> >>
> >>This fixes Ticket #3491
> >>---
> >>  libavformat/matroska.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >>diff --git a/libavformat/matroska.c b/libavformat/matroska.c
> >>index e8e9996..7dc09b3 100644
> >>--- a/libavformat/matroska.c
> >>+++ b/libavformat/matroska.c
> >>@@ -67,9 +67,9 @@ const CodecTags ff_mkv_codec_tags[]={
> >>      {"S_TEXT/UTF8"      , AV_CODEC_ID_SRT},
> >>      {"S_TEXT/ASCII"     , AV_CODEC_ID_TEXT},
> >>  #if FF_API_ASS_SSA
> >>-    {"S_TEXT/ASS"       , AV_CODEC_ID_SSA},
> >>+    {"S_TEXT/ASS"       , AV_CODEC_ID_ASS},
> >>      {"S_TEXT/SSA"       , AV_CODEC_ID_SSA},
> >>-    {"S_ASS"            , AV_CODEC_ID_SSA},
> >>+    {"S_ASS"            , AV_CODEC_ID_ASS},
> >>      {"S_SSA"            , AV_CODEC_ID_SSA},
> >>  #endif
> >>      {"S_TEXT/ASS"       , AV_CODEC_ID_ASS},
> >
> >This was for compatibility, look below the #if/#endif. "SSA" packets were
> >still preferred, but maybe we can remove that ifdefery now.
> >
> >(Note that I didn't look at the ticket yet)
> As far as I understand, this #if/#endif block is used only if we use new
> API, which was introduced with the ASS/SSA split. If FF_API_ASS_SSA is not
> defined, we use old api with old ASS (and without SSA).
> 
> If the old API is not used anymore, it might be better to always use
> #if/#endif block and remove the block below.

See 7c1a002c

tl;dr: AV_CODEC_ID_SSA is the old re-crafted hack format, AV_CODEC_ID_ASS
is the new verbatim data from mkv. Until the next bump (FF_API_ASS_SSA
ifdefery), we still continue to re-craft the packets because the
applications might be relying on that format instead. When we will bump,
the FF_API_ASS_SSA chunk will disappear and the verbatim format will be
choosen.

-- 
Clément B.
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