[FFmpeg-devel] [PATCH v2] avformat/hls: Properly expose intercepted ID3 tags to the API.

[rshaffer at tunein.com]

From: Richard Shaffer <rshaffer at tunein.com>

The HLS demuxer will process any ID3 tags at the beginning of a segment in
order to obtain timestamp data. However, when this data was parsed on a second
or subsequent segment, the updated metadata would be discarded. This change
preserves the data and also sets the AVSTREAM_EVENT_FLAG_METADATA_UPDATED
event flag when appropriate.
---

Changes in this version:
* Only set metadata updated flag if we have non-timestamp metadata.
* Fix clearing of metadata updated flag in hls_read_header.
* Specifically cast operands to unsigned when using bitwise operators.

(This last one is almost certainly pedantic, but it doesn't hurt anything.)

 libavformat/hls.c | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/libavformat/hls.c b/libavformat/hls.c
index 3d4f7f2647..342a022975 100644
--- a/libavformat/hls.c
+++ b/libavformat/hls.c
@@ -982,18 +982,8 @@ static void parse_id3(AVFormatContext *s, AVIOContext *pb,
 }
 
 /* Check if the ID3 metadata contents have changed */
-static int id3_has_changed_values(struct playlist *pls, AVDictionary *metadata,
-                                  ID3v2ExtraMetaAPIC *apic)
+static int id3_has_changed_values(struct playlist *pls, ID3v2ExtraMetaAPIC *apic)
 {
-    AVDictionaryEntry *entry = NULL;
-    AVDictionaryEntry *oldentry;
-    /* check that no keys have changed values */
-    while ((entry = av_dict_get(metadata, "", entry, AV_DICT_IGNORE_SUFFIX))) {
-        oldentry = av_dict_get(pls->id3_initial, entry->key, NULL, AV_DICT_MATCH_CASE);
-        if (!oldentry || strcmp(oldentry->value, entry->value) != 0)
-            return 1;
-    }
-
     /* check if apic appeared */
     if (apic && (pls->ctx->nb_streams != 2 || !pls->ctx->streams[1]->attached_pic.data))
         return 1;
@@ -1019,6 +1009,19 @@ static void handle_id3(AVIOContext *pb, struct playlist *pls)
     int64_t timestamp = AV_NOPTS_VALUE;
 
     parse_id3(pls->ctx, pb, &metadata, &timestamp, &apic, &extra_meta);
+    ff_id3v2_parse_priv_dict(&metadata, &extra_meta);
+    av_dict_copy(&pls->ctx->metadata, metadata, 0);
+    /*
+     * If we've handled any ID3 metadata here, it's not going to be seen by the
+     * sub-demuxer. In the case that we got here because of an IO call during
+     * hls_read_header, this will be cleared. Otherwise, it provides the
+     * necessary hint to hls_read_packet that there is new metadata. Note that
+     * we only set the update flag if we have metadata other than a timestamp.
+     */
+    if (av_dict_count(metadata) > (timestamp == AV_NOPTS_VALUE ? 0 : 1)) {
+        pls->ctx->event_flags = (unsigned)pls->ctx->event_flags |
+            (unsigned)AVFMT_EVENT_FLAG_METADATA_UPDATED;
+    }
 
     if (timestamp != AV_NOPTS_VALUE) {
         pls->id3_mpegts_timestamp = timestamp;
@@ -1037,12 +1040,10 @@ static void handle_id3(AVIOContext *pb, struct playlist *pls)
             /* demuxer not yet opened, defer picture attachment */
             pls->id3_deferred_extra = extra_meta;
 
-        ff_id3v2_parse_priv_dict(&metadata, &extra_meta);
-        av_dict_copy(&pls->ctx->metadata, metadata, 0);
         pls->id3_initial = metadata;
 
     } else {
-        if (!pls->id3_changed && id3_has_changed_values(pls, metadata, apic)) {
+        if (!pls->id3_changed && id3_has_changed_values(pls, apic)) {
             avpriv_report_missing_feature(pls->ctx, "Changing ID3 metadata in HLS audio elementary stream");
             pls->id3_changed = 1;
         }
@@ -1939,8 +1940,16 @@ static int hls_read_header(AVFormatContext *s)
          * Copy any metadata from playlist to main streams, but do not set
          * event flags.
          */
-        if (pls->n_main_streams)
+        if (pls->n_main_streams) {
             av_dict_copy(&pls->main_streams[0]->metadata, pls->ctx->metadata, 0);
+            /*
+             * If we've intercepted metadata, we will have set this event flag.
+             * Clear it to avoid confusion, since otherwise we will flag it as
+             * new metadata on the next call to hls_read_packet.
+             */
+            pls->ctx->event_flags = (unsigned)pls->ctx->event_flags &
+                ~(unsigned)AVFMT_EVENT_FLAG_METADATA_UPDATED;
+        }
 
         add_metadata_from_renditions(s, pls, AVMEDIA_TYPE_AUDIO);
         add_metadata_from_renditions(s, pls, AVMEDIA_TYPE_VIDEO);
-- 
2.15.1 (Apple Git-101)