rtsp mjpeg: Missing packets; dropping frame.

[wose]

I have a rtsp mjpeg stream which doesn't start playing with ffmpeg/ffplay.

ffplay version N-113236-g90bef6390f Copyright (c) 2003-2024 the FFmpeg developers
  built with gcc 13.2.1 (GCC) 20230801
  configuration:
  libavutil      58. 36.101 / 58. 36.101
  libavcodec     60. 37.100 / 60. 37.100
  libavformat    60. 20.100 / 60. 20.100
  libavdevice    60.  4.100 / 60.  4.100
  libavfilter     9. 17.100 /  9. 17.100
  libswscale      7.  6.100 /  7.  6.100
  libswresample   4. 13.100 /  4. 13.100
Initialized opengl renderer.
[tcp @ 0x7f4844003780] No default whitelist set
[tcp @ 0x7f4844003780] Original list of addresses:
[tcp @ 0x7f4844003780] Address 192.168.3.3 port 654
[tcp @ 0x7f4844003780] Interleaved list of addresses:
[tcp @ 0x7f4844003780] Address 192.168.3.3 port 654
[tcp @ 0x7f4844003780] Starting connection attempt to 192.168.3.3 port 654
[tcp @ 0x7f4844003780] Successfully connected to 192.168.3.3 port 654
[rtsp @ 0x7f4844000c80] SDP:
v=0
o=- 0 0 IN IP4 0.0.0.0
s=
i=
c=IN IP4 0.0.0.0
t=0 0
m=video 0 RTP/AVP 26
a=rtpmap:26 JPEG/90000
a=control:rtsp://192.168.3.3:654/00000001-0000-babe-0000-00075f92e21d/live

[rtsp @ 0x7f4844000c80] video codec set to: mjpeg
[rtp @ 0x7f4844009980] No default whitelist set
[udp @ 0x7f4844009cc0] No default whitelist set
[udp @ 0x7f4844009cc0] end receive buffer size reported is 425984
[udp @ 0x7f484401a000] No default whitelist set
[udp @ 0x7f484401a000] end receive buffer size reported is 425984
[rtsp @ 0x7f4844000c80] setting jitter buffer size to 500
[rtsp @ 0x7f4844000c80] hello state=0
[rtsp @ 0x7f4844000c80] Missing packets; dropping frame.
    Last message repeated 18 times
[rtsp @ 0x7f4844000c80] Missing packets; dropping frame. 0B f=0/0
    Last message repeated 18 times
...

The stream does play in vlc (master branch).

I managed to make the stream play using ffplay by disabling the check for missed packets in rtpdec_jpeg.c

diff --git a/libavformat/rtpdec_jpeg.c b/libavformat/rtpdec_jpeg.c
index b32d074136..1988da0853 100644
--- a/libavformat/rtpdec_jpeg.c
+++ b/libavformat/rtpdec_jpeg.c
@@ -350,7 +350,8 @@ static int jpeg_parse_packet(AVFormatContext *ctx, PayloadContext *jpeg,
         return AVERROR_INVALIDDATA;
     }
 
-    if (off != avio_tell(jpeg->frame) - jpeg->hdr_size) {
+    int64_t sz = avio_tell(jpeg->frame) - jpeg->hdr_size;
+    if (off != sz && off != sz + 132) {
         av_log(ctx, AV_LOG_ERROR,
                "Missing packets; dropping frame.\n");
         return AVERROR(EAGAIN);
--

There are always 132 bytes additional bytes which are not expected.
I attached a dump of the UDP stream.

[wose]

Wireshark dump of the UDP stream