Re: [FFmpeg-devel] [PATCH]Tell users about Closed Captions in video streams

[Carl Eugen Hoyos]

On Monday 06 July 2015 06:18:14 pm Carl Eugen Hoyos wrote:
> Hendrik Leppkes <h.leppkes <at> gmail.com> writes:
> > > Attached patch adds "Closed Captions" to the codec
> > > dump if the video stream contains them.
> >
> > Adding fields to a public context which should never
> > be accessed by the public is a big no-no.
>
> What is the alternative?

As in attached?

Carl Eugen

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index e367399..cc71f10 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -3171,6 +3171,14 @@ typedef struct AVCodecContext {
      * - decoding: set by user through AVOPtions (NO direct access)
      */
     char *codec_whitelist;
+
+    /**
+     * Set if the (video) stream contains internal Closed Captions
+     * To be accessed through av_codec_get_closed_captions() (NO direct access)
+     * - encoding: unused
+     * - decoding: set by libavcodec
+     */
+    int closed_captions;
 } AVCodecContext;
 
 AVRational av_codec_get_pkt_timebase         (const AVCodecContext *avctx);
@@ -3185,6 +3193,12 @@ void av_codec_set_lowres(AVCodecContext *avctx, int val);
 int  av_codec_get_seek_preroll(const AVCodecContext *avctx);
 void av_codec_set_seek_preroll(AVCodecContext *avctx, int val);
 
+/**
+ * Returns >0 if Closed Captions were found in the (video) stream
+ * Returns 0 if no Closed Captions were found in the (video) stream
+ */
+int av_codec_get_closed_captions(const AVCodecContext *avctx);
+
 uint16_t *av_codec_get_chroma_intra_matrix(const AVCodecContext *avctx);
 void av_codec_set_chroma_intra_matrix(AVCodecContext *avctx, uint16_t *val);
 
diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index f62ad6a..824abd6 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -886,6 +886,7 @@ static void decode_postinit(H264Context *h, int 
setup_finished)
             memcpy(sd->data, h->a53_caption, h->a53_caption_size);
         av_freep(&h->a53_caption);
         h->a53_caption_size = 0;
+        h->avctx->closed_captions = 1;
     }
 
     cur->mmco_reset = h->mmco_reset;
diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index b0e5ae9..c250d55 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -1685,6 +1685,7 @@ static int mpeg_field_start(MpegEncContext *s, const 
uint8_t *buf, int buf_size)
             if (sd)
                 memcpy(sd->data, s1->a53_caption, s1->a53_caption_size);
             av_freep(&s1->a53_caption);
+            avctx->closed_captions = 1;
         }
 
         if (s1->has_stereo3d) {
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index b80b4e7..a875f7c 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -1299,6 +1299,11 @@ MAKE_ACCESSORS(AVCodecContext, codec, int, lowres)
 MAKE_ACCESSORS(AVCodecContext, codec, int, seek_preroll)
 MAKE_ACCESSORS(AVCodecContext, codec, uint16_t*, chroma_intra_matrix)
 
+int av_codec_get_closed_captions(const AVCodecContext *codec)
+{
+    return codec->closed_captions;
+}
+
 int av_codec_get_max_lowres(const AVCodec *codec)
 {
     return codec->max_lowres;
@@ -3136,6 +3141,10 @@ void avcodec_string(char *buf, int buf_size, 
AVCodecContext *enc, int encode)
         if (encode) {
             snprintf(buf + strlen(buf), buf_size - strlen(buf),
                      ", q=%d-%d", enc->qmin, enc->qmax);
+        } else {
+            if (enc->closed_captions)
+                snprintf(buf + strlen(buf), buf_size - strlen(buf),
+                         ", Closed Captions");
         }
         break;
     case AVMEDIA_TYPE_AUDIO:

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