diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 0758152b3a..424ab38963 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -1649,7 +1649,7 @@ static int mp4_read_iods(AVFormatContext *s, const uint8_t *buf, unsigned size,
 
     ret = parse_mp4_descr(&d, avio_tell(&d.pb), size, MP4IODescrTag);
 
-    *descr_count = d.descr_count;
+    *descr_count += d.descr_count;
     return ret;
 }
 
@@ -2355,7 +2355,7 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
             get8(&p, p_end); // label
             len -= 2;
             mp4_read_iods(ts->stream, p, len, mp4_descr + mp4_descr_count,
-                          &mp4_descr_count, MAX_MP4_DESCR_COUNT);
+                          &mp4_descr_count, MAX_MP4_DESCR_COUNT - mp4_descr_count);
         } else if (tag == REGISTRATION_DESCRIPTOR && len >= 4) {
             prog_reg_desc = bytestream_get_le32(&p);
             len -= 4;