vorbis: handle special packets in the middle of a stream

This allows for updating metadata from new metadata packets in the
middle of a stream (e.g., MPD streams). There still needs to be a signal
that there *is* new metadata, but this is at least gets the data into a
data structure.

Signed-off-by: Ben Boeckel <mathstuf@gmail.com>
Reviewed-by: wm4 <nfxjfg@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/vorbis_parser.c

@@ -201,8 +201,8 @@ int avpriv_vorbis_parse_extradata(AVCodecContext *avctx, VorbisParseContext *s)
     return 0;
 }
 
-int avpriv_vorbis_parse_frame(VorbisParseContext *s, const uint8_t *buf,
+int avpriv_vorbis_parse_frame_flags(VorbisParseContext *s, const uint8_t *buf,
-                              int buf_size)
+                                    int buf_size, int *flags)
 {
     int duration = 0;
 
@@ -211,6 +211,22 @@ int avpriv_vorbis_parse_frame(VorbisParseContext *s, const uint8_t *buf,
         int previous_blocksize = s->previous_blocksize;
 
         if (buf[0] & 1) {
+            /* If the user doesn't care about special packets, it's a bad one. */
+            if (!flags)
+                goto bad_packet;
+
+            /* Set the flag for which kind of special packet it is. */
+            if (buf[0] == 1)
+                *flags |= VORBIS_FLAG_HEADER;
+            else if (buf[0] == 3)
+                *flags |= VORBIS_FLAG_COMMENT;
+            else
+                goto bad_packet;
+
+            /* Special packets have no duration. */
+            return 0;
+
+bad_packet:
             av_log(s->avctx, AV_LOG_ERROR, "Invalid packet\n");
             return AVERROR_INVALIDDATA;
         }
@@ -234,6 +250,12 @@ int avpriv_vorbis_parse_frame(VorbisParseContext *s, const uint8_t *buf,
     return duration;
 }
 
+int avpriv_vorbis_parse_frame(VorbisParseContext *s, const uint8_t *buf,
+                              int buf_size)
+{
+    return avpriv_vorbis_parse_frame_flags(s, buf, buf_size, NULL);
+}
+
 void avpriv_vorbis_parse_reset(VorbisParseContext *s)
 {
     if (s->valid_extradata)

libavcodec/vorbis_parser.h

@@ -50,6 +50,24 @@ typedef struct VorbisParseContext {
  */
 int avpriv_vorbis_parse_extradata(AVCodecContext *avctx, VorbisParseContext *s);
 
+#define VORBIS_FLAG_HEADER  0x00000001
+#define VORBIS_FLAG_COMMENT 0x00000002
+
+/**
+ * Get the duration for a Vorbis packet.
+ *
+ * avpriv_vorbis_parse_extradata() must have been successfully called prior to
+ * this in order for a correct duration to be returned. If @p flags is @c NULL,
+ * special frames are considered invalid.
+ *
+ * @param s        Vorbis parser context
+ * @param buf      buffer containing a Vorbis frame
+ * @param buf_size size of the buffer
+ * @param flags    flags for special frames
+ */
+int avpriv_vorbis_parse_frame_flags(VorbisParseContext *s, const uint8_t *buf,
+                                    int buf_size, int *flags);
+
 /**
  * Get the duration for a Vorbis packet.
  *