Invalid skip of segments on bad/slow network connections

[SuRGeoNix]

By opening a "network" url (tested with hls/rtsp urls) and applying a low bandwidth limit (5-10KB/s) you can reproduce this is issue that skips segments when it shouldn't. Tested with ffplay/mpv.

hls output (ffplay)

[hls @ 0000017125c0f1c0] Opening 'http://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mp4/media_w2141201946_2.ts' for reading
[http @ 0000017125c3c180] Stream ends prematurely at 140844, should be 237444
[http @ 0000017125c47680] Opening 'http://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mp4/media_w2141201946_3.ts' for reading
[hls @ 0000017125c0f1c0] Opening 'http://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mp4/media_w2141201946_3.ts' for reading
[mpegts @ 0000017125c32e00] PES packet size mismatch=    0B f=0/0
[mpegts @ 0000017125c32e00] Packet corrupt (stream = 1, dts = 1473750).
[h264 @ 000001712b87ab40] Invalid NAL unit 0, skipping.  0B f=0/0
[h264 @ 000001712b87ab40] error while decoding MB 5 6, bytestream -17
[h264 @ 000001712b87ab40] concealing 104 DC, 104 AC, 104 MV errors in P frame

hls output (mpv)

mpv http://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mp4/playlist.m3u8
 (+) Video --vid=1 (h264 240x160 24.000fps) (389 kbps)
 (+) Audio --aid=1 (aac 2ch 12000Hz) (389 kbps)
AO: [wasapi] 48000Hz stereo 2ch float
VO: [gpu] 240x160 yuv420p
AV: 00:00:11 / 00:09:56 (2%) A-V:  0.000 Dropped: 5 Cache: 3.4s/124KB
[ffmpeg] http: Stream ends prematurely at 140844, should be 237444
(Buffering) AV: 00:00:15 / 00:09:56 (3%) A-V:  0.000 Dropped: 5 Cache: 0.0s/4KB
[ffmpeg/demuxer] mpegts: PES packet size mismatch
[ffmpeg/demuxer] mpegts: Packet corrupt (stream = 1, dts = 1473750).
AV: 00:00:15 / 00:09:56 (3%) A-V:  0.066 Dropped: 5 Cache: 7.8s/52KB
[ffmpeg/video] h264: Invalid NAL unit 0, skipping.
AV: 00:00:15 / 00:09:56 (3%) A-V:  0.026 Dropped: 5 Cache: 7.8s/50KB
[ffmpeg/video] h264: error while decoding MB 5 6, bytestream -17
AV: 00:00:16 / 00:09:56 (3%) A-V:  0.000 Dropped: 6 Cache: 0.7s/27KB
Invalid audio PTS: 16.384000 -> 23.125333
Reset playback due to audio timestamp reset.
(...) AV: 00:00:00 / 00:09:56 (0%) A-V:  0.000 Cache: 0.0s

rtsp output (mpv)

mpv rtsp://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mov
 (+) Video --vid=1 (h264 240x160 24.000fps)
 (+) Audio --aid=1 (aac 2ch 12000Hz)
File tags:
 Title: BigBuckBunny_115k.mov
AO: [wasapi] 48000Hz stereo 2ch float
VO: [gpu] 240x160 yuv420p
Invalid video timestamp: 0.208333 -> 0.000000
AV: 00:00:25 / 00:09:56 (4%) A-V:  0.480 ct:  0.208 Dropped: 7

Audio/Video desynchronisation detected! Possible reasons include too slow
hardware, temporary CPU spikes, broken drivers, and broken files. Audio
position will not match to the video (see A-V status field).

AV: 00:00:31 / 00:09:56 (5%) A-V:  0.000 ct:  0.208 Dropped: 24
Invalid audio PTS: 32.341333 -> 34.303667
AV: 00:00:56 / 00:09:56 (9%) A-V:  0.000 ct:  2.171 Dropped: 47
Invalid audio PTS: 56.490333 -> 60.501667
AV: 00:00:56 / 00:09:56 (9%) A-V:  0.000 ct:  2.171 Dropped: 47

attached: HLS max offset log