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/srgssr.py b/yt_dlp/extractor/srgssr.py
index ac018e740..2977b5e67 100644
--- a/yt_dlp/extractor/srgssr.py
+++ b/yt_dlp/extractor/srgssr.py
@@ -87,6 +87,7 @@ class SRGSSRIE(InfoExtractor):
         title = media_data['title']
 
         formats = []
+        subtitles = {}
         q = qualities(['SD', 'HD'])
         for source in (media_data.get('resourceList') or []):
             format_url = source.get('url')
@@ -104,12 +105,16 @@ class SRGSSRIE(InfoExtractor):
                 if source.get('tokenType') == 'AKAMAI':
                     format_url = self._get_tokenized_src(
                         format_url, media_id, format_id)
-                    formats.extend(self._extract_akamai_formats(
-                        format_url, media_id))
+                    fmts, subs = self._extract_akamai_formats_and_subtitles(
+                        format_url, media_id)
+                    formats.extend(fmts)
+                    subtitles = self._merge_subtitles(subtitles, subs)
                 elif protocol == 'HLS':
-                    formats.extend(self._extract_m3u8_formats(
+                    m3u8_fmts, m3u8_subs = self._extract_m3u8_formats_and_subtitles(
                         format_url, media_id, 'mp4', 'm3u8_native',
-                        m3u8_id=format_id, fatal=False))
+                        m3u8_id=format_id, fatal=False)
+                    formats.extend(m3u8_fmts)
+                    subtitles = self._merge_subtitles(subtitles, m3u8_subs)
             elif protocol in ('HTTP', 'HTTPS'):
                 formats.append({
                     'format_id': format_id,
@@ -133,7 +138,6 @@ class SRGSSRIE(InfoExtractor):
                 })
         self._sort_formats(formats)
 
-        subtitles = {}
         if media_type == 'video':
             for sub in (media_data.get('subtitleList') or []):
                 sub_url = sub.get('url')