[FFmpeg-devel] [PATCH] avcodec/avformat: Store SDP attributes from RTSP stream into AVStream side data.

[Bernardo Pilarz via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

Connecting to an RTSP stream will now cause the SDP attributes of each media
stream to be stored in the codecpar of the relative AVStream.
The SDP attributes are stored in the coded_side_data using the (new) type
AV_PKT_DATA_SDP_ATTRIBUTES (AVPacketSideDataType enum).

Signed-off-by: bpilarz <bernardo.pilarz@aitek.it>
---
  libavcodec/packet.h |  7 ++++
  libavformat/rtsp.c  | 97 +++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 104 insertions(+)

diff --git a/libavcodec/packet.h b/libavcodec/packet.h
index 13667ffa36..3091c3ce56
--- a/libavcodec/packet.h
+++ b/libavcodec/packet.h
@@ -339,6 +339,13 @@ enum AVPacketSideDataType {
       */
      AV_PKT_DATA_FRAME_CROPPING,
  
+    /**
+     * Attributes found in the SDP, associated with the stream. This is a
+     * list of zero terminated key/value strings. There is no end marker for
+     * the list, so it is required to rely on the side data size to stop.
+     */
+    AV_PKT_DATA_SDP_ATTRIBUTES,
+
      /**
       * The number of side data types.
       * This is not part of the public API/ABI in the sense that it may
diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
index 19b93df839..10594e501a
--- a/libavformat/rtsp.c
+++ b/libavformat/rtsp.c
@@ -283,6 +283,91 @@ static int init_satip_stream(AVFormatContext *s)
  }
  #endif
  
+static int sdp_add_attribute_to_stream_side_data(AVFormatContext *s,
+                                                 AVStream *st,
+                                                 const char *p)
+{
+    AVPacketSideData *side_data = NULL;
+    AVDictionary* attributes_dict = NULL;
+    char *key = NULL, *value = NULL;
+    int ret = 0;
+
+    /* Get the stream's attributes dictionary.
+     * If the stream has no attributes dictionary, it will be automatically
+     * created by av_dict_set. */
+    side_data = av_packet_side_data_get(st->codecpar->coded_side_data,
+                                        st->codecpar->nb_coded_side_data,
+                                        AV_PKT_DATA_SDP_ATTRIBUTES);
+    if (side_data) {
+        ret = av_packet_unpack_dictionary(side_data->data, side_data->size,
+                                          &attributes_dict);
+        if (ret) {
+            av_log(s, AV_LOG_WARNING,
+                   "Unable to unpack SDP attributes dictionary.\n");
+            return -1;
+        }
+    }
+
+    /* The attribute can either be a value attribute (key:value) or
+     * property attribute (just the key).
+     * Look for the ':' separator, and create the 'key' and 'value'
+     * appropriately. */
+    const char *separator = strchr(p, ':');
+    if (separator) {
+        /* Make a copy of the key and value. */
+        key = av_strndup(p, separator - p);
+        value = av_strdup(separator + 1);
+    } else {
+        /* Copy the key and create an empty value. */
+        key = av_strdup(p);
+        value = av_mallocz(1);
+    }
+    if (!key || !value) {
+        av_dict_free(&attributes_dict);
+        av_free(value);
+        av_free(key);
+        return -1;
+    }
+
+    /* Add the attribute, then pack the dictionary again. */
+    ret = av_dict_set(&attributes_dict, key, value,
+                      AV_DICT_DONT_STRDUP_KEY |
+                      AV_DICT_DONT_STRDUP_VAL |
+                      AV_DICT_MULTIKEY);
+    if (ret) {
+        av_log(s, AV_LOG_WARNING,
+               "Unable to add SDL attribute to dictionary.\n");
+        av_dict_free(&attributes_dict);
+        return -1;
+    }
+    size_t packed_dict_size = 0u;
+    uint8_t *packed_dict = av_packet_pack_dictionary(attributes_dict,
+                                                     &packed_dict_size);
+
+    /* Free the dictionary, which is not needed any longer. */
+    av_dict_free(&attributes_dict);
+
+    /* Make sure the dictionary was packet successfully, then add it
+     * back to the stream's side data. */
+    if (!packed_dict) {
+        av_log(s, AV_LOG_WARNING,
+               "Unable to pack SDP attributes dictionary.\n");
+        return -1;
+    }
+    side_data = av_packet_side_data_add(&st->codecpar->coded_side_data,
+                                        &st->codecpar->nb_coded_side_data,
+                                        AV_PKT_DATA_SDP_ATTRIBUTES,
+                                        packed_dict, packed_dict_size,
+                                        0);
+    if (!side_data) {
+        av_log(s, AV_LOG_WARNING,
+               "Unable to add SDP attributes side data to stream.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
  /* parse the rtpmap description: <codec_name>/<clock_rate>[/<other params>] */
  static int sdp_parse_rtpmap(AVFormatContext *s,
                              AVStream *st, RTSPStream *rtsp_st,
@@ -570,6 +655,18 @@ static void sdp_parse_line(AVFormatContext *s, SDPParseState *s1,
                     sizeof(rtsp_st->control_url));
          break;
      case 'a':
+        /* add all SDP attributes to the stream's side data */
+        if (rt->nb_rtsp_streams > 0) {
+            rtsp_st = rt->rtsp_streams[rt->nb_rtsp_streams - 1];
+            if (rtsp_st->stream_index >= 0) {
+                st = s->streams[rtsp_st->stream_index];
+                if (sdp_add_attribute_to_stream_side_data(s, st, p)) {
+                    av_log(s, AV_LOG_WARNING,
+                           "Failed to add SDP attribute to stream");
+                }
+            }
+        }
+        /* now parse the SDP attribute line */
          if (av_strstart(p, "control:", &p)) {
              if (rt->nb_rtsp_streams == 0) {
                  if (!strncmp(p, "rtsp://", 7))
-- 
2.43.0


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