Apple HLS / WWDC downloads stuttering when played back

[lypanov]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2020.06.16.1
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar bug reports including closed ones
• I've read bugs section in FAQ
• I've spent hours Googling and trying every other method I can think of.

Verbose log(s)

NATIVE HLS

$ youtube-dl --hls-prefer-native -f hls-324 https://developer.apple.com/videos/play/wwdc2020/102/ -v
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['--hls-prefer-native', '-f', 'hls-324', 'https://developer.apple.com/videos/play/wwdc2020/102/', '-v']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2020.06.16.1
[debug] Python version 3.8.3 (CPython) - Linux-4.14.83-17437689-aarch64-with-glibc2.17
[debug] exe versions: ffmpeg 4.2.3, ffprobe 4.2.3
[debug] Proxy map: {}
[generic] 102: Requesting header
[generic] 102: Downloading webpage
WARNING: Falling back on generic information extractor.
[generic] 102: Extracting information
[generic] 102: Downloading m3u8 information
[download] Downloading playlist: Platforms State of the Union - WWDC 2020 - Videos - Apple Developer
[generic] playlist Platforms State of the Union - WWDC 2020 - Videos - Apple Developer: Collected 1 video ids (downloading 1 of them)
[download] Downloading video 1 of 1
[debug] Invoking downloader on 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/prog_index.m3u8'
[hlsnative] Downloading m3u8 manifest
[hlsnative] Total fragments: 893
[download] Destination: Platforms State of the Union - WWDC 2020 - Videos - Apple Developer-102.mp4
[download] 100% of 165.81MiB in 14:43
[debug] ffmpeg command line: ffprobe -show_streams 'file:Platforms State of the Union - WWDC 2020 - Videos - Apple Developer-102.mp4'
[download] Finished downloading playlist: Platforms State of the Union - WWDC 2020 - Videos - Apple Developer

FFMPEG HLS

$ youtube-dl -f hls-324 https://developer.apple.com/videos/play/wwdc2020/102/ -v
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-f', 'hls-324', 'https://developer.apple.com/videos/play/wwdc2020/102/', '-v']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2020.06.16.1
[debug] Python version 3.8.3 (CPython) - Linux-4.14.83-17437689-aarch64-with-glibc2.17
[debug] exe versions: ffmpeg 4.2.3, ffprobe 4.2.3
[debug] Proxy map: {}
[generic] 102: Requesting header
[generic] 102: Downloading webpage
WARNING: Falling back on generic information extractor.
[generic] 102: Extracting information
[generic] 102: Downloading m3u8 information
[download] Downloading playlist: Platforms State of the Union - WWDC 2020 - Videos - Apple Developer
[generic] playlist Platforms State of the Union - WWDC 2020 - Videos - Apple Developer: Collected 1 video ids (downloading 1 of them)
[download] Downloading video 1 of 1
[debug] Invoking downloader on 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/prog_index.m3u8'
[download] Destination: Platforms State of the Union - WWDC 2020 - Videos - Apple Developer-102.mp4
[debug] ffmpeg command line: ffmpeg -y -loglevel verbose -headers 'User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.43 Safari/537.36
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding: gzip, deflate
Accept-Language: en-us,en;q=0.5
Referer: https://developer.apple.com/videos/play/wwdc2020/102/
' -i https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/prog_index.m3u8 -c copy -f mp4 'file:Platforms State of the Union - WWDC 2020 - Videos - Apple Developer-102.mp4.part'
ffmpeg version n4.2.3 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3.0 (GCC)
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libdav1d --enable-libdrm --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libjack --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-omx --enable-shared --enable-version3 --host-cflags='"-fPIC"'
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
[tcp @ 0x300009de10] Starting connection attempt to 17.253.53.207 port 443
[tcp @ 0x300009de10] Successfully connected to 17.253.53.207 port 443
[hls @ 0x300009b490] Skip ('#EXT-X-VERSION:7')
[hls @ 0x300009b490] Skip ('#EXT-X-INDEPENDENT-SEGMENTS')
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:370')
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:470')
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:574')
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:941')
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:1306')
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:1858')
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:306')
<CUT>
[hls @ 0x300009b490] Skip ('#EXT-X-BITRATE:104')
[hls @ 0x300009b490] HLS request for url 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_0.mp4', offset 0, playlist 0
[hls @ 0x300009b490] Opening 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_0.mp4' for reading
[tcp @ 0x30006db230] Starting connection attempt to 17.253.105.204 port 443
[tcp @ 0x30006db230] Successfully connected to 17.253.105.204 port 443
[AVIOContext @ 0x300073f580] Statistics: 713 bytes read, 0 seeks
[hls @ 0x300009b490] HLS request for url 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_1.mp4', offset 0, playlist 0
[hls @ 0x300009b490] Opening 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_1.mp4' for reading
[tcp @ 0x300012dfc0] Starting connection attempt to 17.253.105.204 port 443
[tcp @ 0x300012dfc0] Successfully connected to 17.253.105.204 port 443
[hls @ 0x300009b490] HLS request for url 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_2.mp4', offset 0, playlist 0
[hls @ 0x300009b490] Opening 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_2.mp4' for reading
[tcp @ 0x30000a0bd0] Starting connection attempt to 17.253.53.209 port 443
[tcp @ 0x30000a0bd0] Successfully connected to 17.253.53.209 port 443
[h264 @ 0x300071b4a0] Reinit context to 960x544, pix_fmt: yuv420p
Input #0, hls, from 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/prog_index.m3u8':
  Duration: 01:29:23.83, start: 10.066733, bitrate: 0 kb/s
  Program 0 
    Metadata:
      variant_bitrate : 0
    Stream #0:0: Video: h264 (Main), 1 reference frame (avc1 / 0x31637661), yuv420p(tv, bt709/bt709/unknown, left), 960x540 (960x544) [SAR 1:1 DAR 16:9], 85 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc
    Metadata:
      variant_bitrate : 0
      major_brand     : iso5
      minor_version   : 1
      compatible_brands: isomiso5hlsf
      creation_time   : 2020-06-20T19:42:52.000000Z
Output #0, mp4, to 'file:Platforms State of the Union - WWDC 2020 - Videos - Apple Developer-102.mp4.part':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: h264 (Main), 1 reference frame (avc1 / 0x31637661), yuv420p(tv, bt709/bt709/unknown, left), 960x540 (0x0) [SAR 1:1 DAR 16:9], q=2-31, 85 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 30k tbc
    Metadata:
      variant_bitrate : 0
      major_brand     : iso5
      minor_version   : 1
      compatible_brands: isomiso5hlsf
      creation_time   : 2020-06-20T19:42:52.000000Z
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 41083, current: 40040; changing to 41084. This may result in incorrect timestamps in the output file.
[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 41084, current: 41041; changing to 41085. This may result in incorrect timestamps in the output file.
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x30006da300] DTS 300000 < 343043 out of order
[hls @ 0x300009b490] DTS 300000 < 343043 out of order
[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 41085, current: -2002; changing to 41086. This may result in incorrect timestamps in the output file.
<CUT>
[hls @ 0x300009b490] HLS request for url 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_892.mp4', offset 0, playlist 0
[https @ 0x3000133d30] Opening 'https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/avc_540p_2000_892.mp4' for reading
frame=160202 fps=492 q=-1.0 size=  167424kB time=01:29:05.30 bitrate= 256.6kbits/s speed=[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 160401241, current: 160358198; changing to 160401242. This may result in incorrect timestamps in the output file.
[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 160401242, current: 160359199; changing to 160401243. This may result in incorrect timestamps in the output file.
<CUT>
[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 160671511, current: 160628468; changing to 160671512. This may result in incorrect timestamps in the output file.
[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 160671512, current: 160629469; changing to 160671513. This may result in incorrect timestamps in the output file.
[ffmpeg] Downloaded 173032304 bytes
[download] 100% of 165.02MiB in 05:29
[download] Finished downloading playlist: Platforms State of the Union - WWDC 2020 - Videos - Apple Developer
<CUT>
p4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 160851735, current: 160808648; changing to 160851736. This may result in incorrect timestamps in the output file.
[mp4 @ 0x300072e680] Non-monotonous DTS in output stream 0:0; previous: 160851736, current: 160809649; changing to 160851737. This may result in incorrect timestamps in the output file.
No more output streams to write to, finishing.
frame=160754 fps=493 q=-1.0 Lsize=  168977kB time=01:29:23.72 bitrate= 258.1kbits/s speed=16.5x    
video:167643kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.795370%
Input file #0 (https://devstreaming-cdn.apple.com/videos/wwdc/2020/102/1/D80F0868-A427-49B2-8422-D79AB307560E/avc_540p_2000/prog_index.m3u8):
  Input stream #0:0 (video): 160754 packets read (171666917 bytes); 
  Total: 160754 packets (171666917 bytes) demuxed
Output file #0 (file:Platforms State of the Union - WWDC 2020 - Videos - Apple Developer-102.mp4.part):
  Output stream #0:0 (video): 160754 packets muxed (171666917 bytes); 
  Total: 160754 packets (171666917 bytes) muxed
[AVIOContext @ 0x30005ddbd0] Statistics: 14 seeks, 671 writeouts
[AVIOContext @ 0x300073f580] Statistics: 85772644 bytes read, 0 seeks
[AVIOContext @ 0x30006d2ba0] Statistics: 88087757 bytes read, 0 seeks
[AVIOContext @ 0x30006a9050] Statistics: 52696 bytes read, 0 seeks

Description

With hls-prefer-native option provided the resulting file is unplayable in the video player I otherwise have perfect results with for youtube-dl.

With ffmpeg HLS the file plays, but, plays back with non stop 500ms pauses/gaps in the output. The output is also so extremely long that I'm unable to paste it in full due to an absurd numbers of the DTS timestamp warnings.