hls demuxer does not handle pid changes after EXT-X-DISCONTINUITY

[Aman]

Summary of the bug:
An HLS playlist can contain EXT-X-DISCONTINUITY tags. The segment after such a tag may contain a new PMT, which may contain new elementary streams on previously used pids.

For example, this m3u8:

#EXTM3U
#EXT-X-VERSION:6
#EXT-X-TARGETDURATION:10
#EXT-X-MEDIA-SEQUENCE:1
#EXT-X-INDEPENDENT-SEGMENTS
#EXTINF:7.074,
segment_156270742.ts
#EXT-X-DISCONTINUITY
#EXTINF:10.101,
segment-1.ts
#EXTINF:10.008,
segment-2.ts
#EXTINF:10.194,
segment-3.ts
#EXT-X-DISCONTINUITY
#EXTINF:10.010,
segment_156270745.ts
#EXT-X-ENDLIST

where segment_156270742.ts before the X-DISCONTINUITY has streams as follows:

  Program 1
    Stream #0:0[0x101]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(progressive), 1920x1080, Closed Captions, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
    Stream #0:1[0x102]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 93 kb/s
    Stream #0:2[0x103]: Data: timed_id3 (ID3  / 0x20334449)

and segment-1.ts after the X-DISCONTINUITY has streams:

  Program 1
    Stream #0:0[0x101]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 69 kb/s
    Stream #0:1[0x102]: Video: h264 (Constrained Baseline) ([27][0][0][0] / 0x001B), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc

Before the discontinuity, 0x101 is a video PID but afterwards it is an audio PID.

ffmpeg does not detect this PMT change, and feeds audio packets into the video decoder and vice versa.

How to reproduce:

% ffmpeg -i https://tmm1.s3.amazonaws.com/hls-pidswap/test.m3u8 -f null -y /dev/null
ffmpeg version git-2019-02-13-bf78aa9 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/HEAD-bf78aa9 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/include/darwin' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-videotoolbox --disable-libjack --disable-indev=jack --enable-libaom --enable-libsoxr
  libavutil      56. 26.100 / 56. 26.100
  libavcodec     58. 47.100 / 58. 47.100
  libavformat    58. 26.101 / 58. 26.101
  libavdevice    58.  6.101 / 58.  6.101
  libavfilter     7. 48.100 /  7. 48.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  4.100 /  5.  4.100
  libswresample   3.  4.100 /  3.  4.100
  libpostproc    55.  4.100 / 55.  4.100
[hls,applehttp @ 0x7f9dd0800000] Opening 'https://tmm1.s3.amazonaws.com/hls-pidswap/segment_156270742.ts' for reading
[hls,applehttp @ 0x7f9dd0800000] Opening 'https://tmm1.s3.amazonaws.com/hls-pidswap/segment-1.ts' for reading
Input #0, hls,applehttp, from 'https://tmm1.s3.amazonaws.com/hls-pidswap/test.m3u8':
  Duration: 00:00:47.39, start: 44058.812000, bitrate: 0 kb/s
  Program 0
    Metadata:
      variant_bitrate : 0
    Stream #0:0: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 1920x1080, Closed Captions, 29.97 tbr, 90k tbn, 59.94 tbc
    Metadata:
      variant_bitrate : 0
    Stream #0:1: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp
    Metadata:
      variant_bitrate : 0
    Stream #0:2: Data: timed_id3 (ID3  / 0x20334449)
    Metadata:
      variant_bitrate : 0
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> wrapped_avframe (native))
  Stream #0:1 -> #0:1 (aac (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, null, to '/dev/null':
  Metadata:
    encoder         : Lavf58.26.101
    Stream #0:0: Video: wrapped_avframe, yuv420p, 1920x1080, q=2-31, 200 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc
    Metadata:
      variant_bitrate : 0
      encoder         : Lavc58.47.100 wrapped_avframe
    Stream #0:1: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
    Metadata:
      variant_bitrate : 0
      encoder         : Lavc58.47.100 pcm_s16le
[https @ 0x7f9dcf01b800] Opening 'https://tmm1.s3.amazonaws.com/hls-pidswap/segment-2.ts' for reading
[aac @ 0x7f9dd103a000] channel element 1.0 is not allocated
Error while decoding stream #0:1: Invalid data found when processing input
[aac @ 0x7f9dd103a000] More than one AAC RDB per ADTS frame is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[aac @ 0x7f9dd103a000] Multiple frames in a packet.
[aac @ 0x7f9dd103a000] Number of bands (45) exceeds limit (32).
Error while decoding stream #0:1: Invalid data found when processing input
[aac @ 0x7f9dd103a000] Prediction is not allowed in AAC-LC.
Error while decoding stream #0:1: Invalid data found when processing input
[aac @ 0x7f9dd103a000] Reserved bit set.
[aac @ 0x7f9dd103a000] invalid band type
Error while decoding stream #0:1: Invalid data found when processing input
[aac @ 0x7f9dd103a000] Sample rate index in program config element does not match the sample rate index configured by the container.
[aac @ 0x7f9dd103a000] Inconsistent channel configuration.
[aac @ 0x7f9dd103a000] get_buffer() failed
Error while decoding stream #0:1: Invalid argument
[aac @ 0x7f9dd103a000] channel element 1.2 is not allocated
Error while decoding stream #0:1: Invalid data found when processing input
[aac @ 0x7f9dd103a000] Number of bands (23) exceeds limit (16).
Error while decoding stream #0:1: Invalid data found when processing input
[aac @ 0x7f9dd103a000] Reserved bit set.
[aac @ 0x7f9dd103a000] Number of bands (37) exceeds limit (19).
Error while decoding stream #0:1: Invalid data found when processing input

[Aman]

Note that popular HLS players such as Safari, Quicktime, hls.js etc have no problem with this playlist.

[Jun Zhao]

duplicate with ​http://trac.ffmpeg.org/ticket/6737

[Marton Balint]

How does a compliant player match the streams? E.g. what if two aac audio streams are in the PMT, and they swap pids?