Assertion fails when reading rtp mpegts streaming using SDP file

[Marek Fort]

Summary of the bug:
You get assertion failure when you try to open a RTP mpegts stream using SDP file.

The problem is that function handle_packet() in avformat/mpegts.c is calling avio_tell(). This is incorrect when it is called from avpriv_mpegts_parse_packet(). In this case the "pb" is not the actual input stream. It is the SDP file!

How to reproduce:

ffplay version N-94212-g98b122cdb9 Copyright (c) 2003-2019 the FFmpeg developers

  built with gcc 9.1.1 (GCC) 20190621
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfi
g --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libb
luray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --e
nable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable
-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 -
-enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enab
le-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --en
able-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --en
able-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --e
nable-dxva2 --enable-avisynth --enable-libopenmpt
  libavutil      56. 30.100 / 56. 30.100
  libavcodec     58. 53.101 / 58. 53.101
  libavformat    58. 28.101 / 58. 28.101
  libavdevice    58.  7.100 / 58.  7.100
  libavfilter     7. 56.101 /  7. 56.101
  libswscale      5.  4.101 /  5.  4.101
  libswresample   3.  4.100 /  3.  4.100
  libpostproc    55.  4.100 / 55.  4.100
[udp @ 00000000004ec100] 'circular_buffer_size' option was set but it is not sup
ported on this build (pthread support is required)
[udp @ 00000000004ec200] 'circular_buffer_size' option was set but it is not sup
ported on this build (pthread support is required)
Assertion pos >= 188 failed at src/libavformat/mpegts.c:2653

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.

[Carl Eugen Hoyos]

If this issue is still reproducible with current FFmpeg git head, please provide the complete, uncut console output together with the command line you tested.

[Balling]

Is this fixed?

[Marek Fort]

Reproduced with latest version e931119...

ffplay rtp_test.sdp -protocol_whitelist "file,rtp,udp"

ffplay version git-2020-01-24-e931119 Copyright (c) 2003-2020 the FFmpeg developers
  built with gcc 9.2.1 (GCC) 20200122
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfi
g --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libb
luray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --e
nable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable
-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 -
-enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enab
le-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --en
able-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-ffnvcode
c --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 -
-enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 38.100 / 56. 38.100
  libavcodec     58. 66.100 / 58. 66.100
  libavformat    58. 35.104 / 58. 35.104
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 71.100 /  7. 71.100
  libswscale      5.  6.100 /  5.  6.100
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
[udp @ 00000000005cc140] 'circular_buffer_size' option was set but it is not supported on this build (pthread support is required)
[udp @ 00000000005cc240] 'circular_buffer_size' option was set but it is not supported on this build (pthread support is required)
[udp @ 00000000005cc340] 'circular_buffer_size' option was set but it is not supported on this build (pthread support is required)
[udp @ 00000000005cc400] 'circular_buffer_size' option was set but it is not supported on this build (pthread support is required)
Assertion pos >= 188 failed at src/libavformat/mpegts.c:2721f=0/0

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0

The SDP file might look like this.

v=0
c=IN IP4 192.168.1.150
m=video 20000 RTP/AVP 33
a=rtpmap:33 MP2T/90000
a=control:mpegts-transport

See the original post. Function handle_packet() in avformat/mpegts.c is calling avio_tell() on ts->stream->pb. But that is not the TS stream! That is the SDP file. The stream is not available to handle_packet at all as it is called from avpriv_mpegts_parse_packet where the packet comes as an argument.

[Carl Eugen Hoyos]

(I cannot reproduce)
Can you reproduce the issue if you provide the source stream with FFmpeg?
Can you reproduce the issue if you remove all lines from the sdp file except c and m?
Can you reproduce the issue with address 127.0.0.1?

[Marek Fort]

Minimal SDP file

c=IN IP4 127.0.0.1
m=video 20000 RTP/AVP 33

Sorry I forgot to mention that the stream must be running. The ffplay needs to parse some TS packets out of the stream and call avpriv_mpegts_parse_packet.

I produce the stream by:

ffmpeg -re -stream_loop -1 -i test.mp4 -vcodec copy -an -f rtp_mpegts rtp://127.0.0.1:20000

The test.mp4 should be h264 stream that is then sent over Mpeg2 TS.

[Carl Eugen Hoyos]

Regression since 0f2f65bd583576ef8c12eea6088c84d4468f5804, reproducible for example with the following command line and above minimal sdp file:

$ ffmpeg -re -f lavfi -i testsrc2 -f rtp_mpegts rtp://127.0.0.1:20000

[Marek Fort]

Commit 0f2f65bd583576ef8c12eea6088c84d4468f5804 added the assert which makes the problem visible. But the problem itself can be traced back to 4c6b49bf74f3a4ae3b198d487b7d3b5b64226778
Function handle_packet should be given the stream position as a parameter and call the tell(stream->pb) outside.

[Carl Eugen Hoyos]

Fixed by Michael in e5bb48ae5990347dff22fc38ff5a1c1f7f60a1c5