Subtitle extraction from streaming media manifests #247

Authored by fstirlitz
Modified from: https://github.com/ytdl-org/youtube-dl/pull/6144

Closes: #73
Fixes:
https://github.com/ytdl-org/youtube-dl/issues/6106
https://github.com/ytdl-org/youtube-dl/issues/14977
https://github.com/ytdl-org/youtube-dl/issues/21438
https://github.com/ytdl-org/youtube-dl/issues/23609
https://github.com/ytdl-org/youtube-dl/issues/28132

Might also fix (untested):
https://github.com/ytdl-org/youtube-dl/issues/15424
https://github.com/ytdl-org/youtube-dl/issues/18267
https://github.com/ytdl-org/youtube-dl/issues/23899
https://github.com/ytdl-org/youtube-dl/issues/24375
https://github.com/ytdl-org/youtube-dl/issues/24595
https://github.com/ytdl-org/youtube-dl/issues/27899

Related:
https://github.com/ytdl-org/youtube-dl/issues/22379
https://github.com/ytdl-org/youtube-dl/pull/24517
https://github.com/ytdl-org/youtube-dl/pull/24886
https://github.com/ytdl-org/youtube-dl/pull/27215

Notes:
* The functions `extractor.common._extract_..._formats` are still kept for compatibility
* Only some extractors have currently been moved to using `_extract_..._formats_and_subtitles`
* Direct subtitle manifests (without a master) are not supported and are wrongly identified as containing video formats
* AES support is untested
* The fragmented TTML subtitles extracted from DASH/ISM are valid, but are unsupported by `ffmpeg` and most video players
    * Their XML fragments can be dumped using `ffmpeg -i in.mp4 -f data -map 0 -c copy out.ttml`.
        Once the unnecessary headers are stripped out of this, it becomes a valid self-contained ttml file
    * The ttml subs downloaded from DASH manifests can also be directly opened with <https://github.com/SubtitleEdit>
* Fragmented WebVTT files extracted from DASH/ISM are also unsupported by most tools
    * Unlike the ttml files, the XML fragments of these cannot be dumped using `ffmpeg`
    * The webtt subs extracted from DASH can be parsed by <https://github.com/gpac/gpac>
    * But validity of the those extracted from ISM are untested

1 files changed, 9 insertions, 5 deletions

diff --git a/yt_dlp/extractor/threeqsdn.py b/yt_dlp/extractor/threeqsdn.py
index 5eaa991eb..bb7610352 100644
--- a/yt_dlp/extractor/threeqsdn.py
+++ b/yt_dlp/extractor/threeqsdn.py
@@ -99,16 +99,21 @@ class ThreeQSDNIE(InfoExtractor):
         aspect = float_or_none(config.get('aspect'))
 
         formats = []
+        subtitles = {}
         for source_type, source in (config.get('sources') or {}).items():
             if not source:
                 continue
             if source_type == 'dash':
-                formats.extend(self._extract_mpd_formats(
-                    source, video_id, mpd_id='mpd', fatal=False))
+                fmts, subs = self._extract_mpd_formats_and_subtitles(
+                    source, video_id, mpd_id='mpd', fatal=False)
+                formats.extend(fmts)
+                subtitles = self._merge_subtitles(subtitles, subs)
             elif source_type == 'hls':
-                formats.extend(self._extract_m3u8_formats(
+                fmts, subs = self._extract_m3u8_formats_and_subtitles(
                     source, video_id, 'mp4', 'm3u8' if live else 'm3u8_native',
-                    m3u8_id='hls', fatal=False))
+                    m3u8_id='hls', fatal=False)
+                formats.extend(fmts)
+                subtitles = self._merge_subtitles(subtitles, subs)
             elif source_type == 'progressive':
                 for s in source:
                     src = s.get('src')
@@ -138,7 +143,6 @@ class ThreeQSDNIE(InfoExtractor):
         # behaviour is being kept as-is
         self._sort_formats(formats, ('res', 'source_preference'))
 
-        subtitles = {}
         for subtitle in (config.get('subtitles') or []):
             src = subtitle.get('src')
             if not src: