avformat/ttml: split TTML paragraph based or not check into header

This way it can be re-utilized in movenc.

Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>

libavformat/ttmlenc.c

@@ -30,6 +30,7 @@
 #include "libavutil/avstring.h"
 #include "avformat.h"
 #include "internal.h"
+#include "ttmlenc.h"
 #include "libavcodec/ttmlenc.h"
 #include "libavutil/internal.h"
 
@@ -138,13 +139,7 @@ static int ttml_write_header(AVFormatContext *ctx)
                                               0);
         const char *printed_lang = (lang && lang->value) ? lang->value : "";
 
-        // Not perfect, but decide whether the packet is a document or not
-        // by the existence of the lavc ttmlenc extradata.
-        ttml_ctx->input_type = (st->codecpar->extradata &&
-                                st->codecpar->extradata_size >= TTMLENC_EXTRADATA_SIGNATURE_SIZE &&
-                                !memcmp(st->codecpar->extradata,
-                                        TTMLENC_EXTRADATA_SIGNATURE,
-                                        TTMLENC_EXTRADATA_SIGNATURE_SIZE)) ?
+        ttml_ctx->input_type = ff_is_ttml_stream_paragraph_based(st->codecpar) ?
                                PACKET_TYPE_PARAGRAPH :
                                PACKET_TYPE_DOCUMENT;
 

libavformat/ttmlenc.h

@@ -0,0 +1,39 @@
+/*
+ * Generic TTML helpers
+ * Copyright (c) 2021 24i
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVFORMAT_TTMLENC_H
+#define AVFORMAT_TTMLENC_H
+
+#include "libavcodec/codec_par.h"
+#include "libavcodec/ttmlenc.h"
+
+static inline unsigned int ff_is_ttml_stream_paragraph_based(const AVCodecParameters *codecpar)
+{
+    // Not perfect, but decide whether the packet is a document or not
+    // by the existence of the lavc ttmlenc extradata.
+    return (codecpar->extradata &&
+            codecpar->extradata_size >= TTMLENC_EXTRADATA_SIGNATURE_SIZE &&
+            !memcmp(codecpar->extradata,
+                    TTMLENC_EXTRADATA_SIGNATURE,
+                    TTMLENC_EXTRADATA_SIGNATURE_SIZE));
+}
+
+#endif /* AVFORMAT_TTMLENC_H */