allow passing subtitles header between decoder and encoder

Originally committed as revision 25745 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -2284,6 +2284,7 @@ static int transcode(AVFormatContext **output_files,
         ost = ost_table[i];
         if (ost->encoding_needed) {
             AVCodec *codec = i < nb_output_codecs ? output_codecs[i] : NULL;
+            AVCodecContext *dec = ist_table[ost->source_index]->st->codec;
             if (!codec)
                 codec = avcodec_find_encoder(ost->st->codec->codec_id);
             if (!codec) {
@@ -2292,6 +2293,15 @@ static int transcode(AVFormatContext **output_files,
                 ret = AVERROR(EINVAL);
                 goto dump_format;
             }
+            if (dec->subtitle_header) {
+                ost->st->codec->subtitle_header = av_malloc(dec->subtitle_header_size);
+                if (!ost->st->codec->subtitle_header) {
+                    ret = AVERROR(ENOMEM);
+                    goto dump_format;
+                }
+                memcpy(ost->st->codec->subtitle_header, dec->subtitle_header, dec->subtitle_header_size);
+                ost->st->codec->subtitle_header_size = dec->subtitle_header_size;
+            }
             if (avcodec_open(ost->st->codec, codec) < 0) {
                 snprintf(error, sizeof(error), "Error while opening encoder for output stream #%d.%d - maybe incorrect parameters such as bit_rate, rate, width or height",
                         ost->file_index, ost->index);
@@ -2690,6 +2700,7 @@ static int transcode(AVFormatContext **output_files,
                 }
                 av_fifo_free(ost->fifo); /* works even if fifo is not
                                              initialized but set to zero */
+                av_freep(&ost->st->codec->subtitle_header);
                 av_free(ost->pict_tmp.data[0]);
                 av_free(ost->forced_kf_pts);
                 if (ost->video_resample)

libavcodec/avcodec.h

@@ -2757,6 +2757,17 @@ typedef struct AVCodecContext {
      * - decoding: unused
      */
     int slices;
+
+    /**
+     * Header containing style information for text subtitles.
+     * For SUBTITLE_ASS subtitle type, it should contain the whole ASS
+     * [Script Info] and [V4+ Styles] section, plus the [Events] line and
+     * the Format line following. It shouldn't include any Dialogue line.
+     * - encoding: Set/allocated/freed by user (before avcodec_open())
+     * - decoding: Set/allocated/freed by libavcodec (by avcodec_open())
+     */
+    uint8_t *subtitle_header;
+    int subtitle_header_size;
 } AVCodecContext;
 
 /**

libavformat/utils.c

@@ -2206,9 +2206,14 @@ int av_find_stream_info(AVFormatContext *ic)
         if (codec && codec->capabilities & CODEC_CAP_CHANNEL_CONF)
             st->codec->channels = 0;
 
+        /* Ensure that subtitle_header is properly set. */
+        if (st->codec->codec_type == AVMEDIA_TYPE_SUBTITLE
+            && codec && !st->codec->codec)
+            avcodec_open(st->codec, codec);
+
         //try to just open decoders, in case this is enough to get parameters
         if(!has_codec_parameters(st->codec)){
-            if (codec)
+            if (codec && !st->codec->codec)
                 avcodec_open(st->codec, codec);
         }
     }
@@ -2471,6 +2476,7 @@ void av_close_input_stream(AVFormatContext *s)
         av_metadata_free(&st->metadata);
         av_free(st->index_entries);
         av_free(st->codec->extradata);
+        av_free(st->codec->subtitle_header);
         av_free(st->codec);
 #if FF_API_OLD_METADATA
         av_free(st->filename);