Subtitle Hide And Seek [Extra Quality]
mpv is a media player based on MPlayer and mplayer2. It supports a wide variety of video file formats, audio and video codecs, and subtitle types. Special input URL types are available to read input from a variety of sources other than disk files. Depending on platform, a variety of different video and audio output methods are supported.
subtitle Hide and Seek
If --rebase-start-time=no is given, then prefixing times with + makes the time relative to the start of the file. A timestamp without prefix is considered an absolute time, i.e. should seek to a frame with a timestamp as the file contains it. As a bug, but also a hidden feature, putting 1 or more spaces before the + or - always interprets the time as absolute, which can be used to seek to negative timestamps (useful for debugging at most).
The difference to --loop-playlist is that this doesn't loop the playlist, just the file itself. If the playlist contains only a single file, the difference between the two option is that this option performs a seek on loop, instead of reloading the file.
If a is after b, the behavior is as if the points were given in the right order, and the player will seek to b after crossing through a. This is different from old behavior, where looping was disabled (and as a bug, looped back to a on the end of the file).
If you just want to quickly go backward through the video and just show "keyframes", just use forward playback, and hold down the left cursor key (which on CLI with default config sends many small relative seek commands).
Changing styling and position does not work with all subtitles. Image-based subtitles (DVD, Bluray/PGS, DVB) cannot changed for fundamental reasons. Subtitles in ASS format are normally not changed intentionally, but overriding them can be controlled with --sub-ass-override.
If --sub-file is used multiple times, the subtitle to use can be switched at runtime by cycling subtitle tracks. It's possible to show two subtitles at once: use --sid to select the first subtitle index, and --secondary-sid to select the second index. (The index is printed on the terminal output after the --sid= in the list of streams.)
There are some caveats associated with this feature. For example, bitmap subtitles will always be rendered in their usual position, so selecting a bitmap subtitle as secondary subtitle will result in overlapping subtitles. Secondary subtitles are never shown on the terminal if video is disabled.
The renderer historically most commonly used for the SSA/ASS subtitle formats, VSFilter, had questionable behavior that resulted in subtitles being stretched too if the video was stored in anamorphic format that required scaling for display. This behavior is usually undesirable and newer VSFilter versions may behave differently. However, many existing scripts compensate for the stretching by modifying things in the opposite direction. Thus, if such scripts are displayed "correctly", they will not appear as intended. This switch enables emulation of the old VSFilter behavior (undesirable but expected by many existing scripts).
Many studios tend to use bitmap fonts designed for square pixels when authoring DVDs, causing the fonts to look stretched on playback on DVD players. This option fixes them, however at the price of possibly misaligning some subtitles (e.g. sign translations).
The pseudo codepage UTF-8-BROKEN is used internally. If it's set, subtitles are interpreted as UTF-8 with "Latin 1" as fallback for bytes which are not valid UTF-8 sequences. iconv is never involved in this mode.
List items are matched in order. If a regular expression matches, the process is stopped, and the subtitle line is discarded. The text matched against is, by default, the Text field of ASS events (if the subtitle format is different, it is always converted). This may include formatting tags. Matching is case-insensitive, but how this is done depends on the libc, and most likely works in ASCII only. It does not work on bitmap/image subtitles. Unavailable on inferior OSes (requires POSIX regex support).
This affects image files, which are defined as having only 1 video frame and no audio. The player may recognize certain non-images as images, for example if --length is used to reduce the length to 1 frame, or if you seek to the last frame.
Enabling this option makes the demuxer start reading data a bit before the seek target, so that subtitles appear correctly. Note that this makes seeking slower, and is not guaranteed to always work. It only works if the subtitle is close enough to the seek target.
You can use the --demuxer-mkv-subtitle-preroll-secs option to specify how much data the demuxer should pre-read at most in order to find subtitle packets that may overlap. Setting this to 0 will effectively disable this preroll mechanism. Setting a very large value can make seeking very slow, and an extremely large value would completely reread the entire file from start to seek target on every seek - seeking can become slower towards the end of the file. The details are messy, and the value is actually rounded down to the cluster with the previous video keyframe.
Some files, especially files muxed with newer mkvmerge versions, have information embedded that can be used to determine what subtitle packets overlap with a seek target. In these cases, mpv will reduce the amount of data read to a minimum. (Although it will still read all data between the cluster that contains the first wanted subtitle packet, and the seek target.) If the index choice (which is the default) is specified, then prerolling will be done only if this information is actually available. If this method is used, the maximum amount of data to skip can be additionally controlled by --demuxer-mkv-subtitle-preroll-secs-index (it still uses the value of the option without -index if that is higher).
See also --hr-seek-demuxer-offset option. This option can achieve a similar effect, but only if hr-seek is active. It works with any demuxer, but makes seeking much slower, as it has to decode audio and video data instead of just skipping over it.
Unlike the forward cache, there is no control how many seconds are actually cached - it will simply use as much memory this option allows. Setting this option to 0 will strictly disable any back buffer, but this will lead to the situation that the forward seek range starts after the current playback position (as it removes past packets that are seek points).
If enabled, short seek offsets will not trigger a low level demuxer seek (which means for example that slow network round trips or FFmpeg seek bugs can be avoided). If a seek cannot happen within the cached range, a low level seek will be triggered. Seeking outside of the cache will start a new cached range, but can discard the old cache range if the demuxer exhibits certain unsupported behavior.
If enabled, use up to --cache-secs for the cache size (but still limited to --demuxer-max-bytes), and make the cached data seekable (if possible). If disabled, --cache-pause and related are implicitly disabled.
This is probably quite pointless. libavcodec already has multithreaded decoding (enabled by default), which makes this largely unnecessary. It might help in some corner cases with high bandwidth video that is slow to decode (in these cases libavcodec would block the playback logic, while using a decoding thread would distribute the decoding time evenly without affecting the playback logic). In other situations, it will simply make seeking slower and use significantly more memory.
Before mpv 0.30.0, there was a fallback to audio mode on severe A/V desync. This was changed for the sake of not sporadically stopping. Now, display-desync does what it promises and may desync with audio by an arbitrary amount, until it is manually fixed with a seek.
The modes with desync in their names do not attempt to keep audio/video in sync. They will slowly (or quickly) desync, until e.g. the next seek happens. These modes are meant for testing, not serious use.
Seeking outside of the demuxer cache will result in "skips" in the output file, but seeking within the demuxer cache should not affect recording. One exception is when you seek back far enough to exceed the forward buffering size, in which case the cache stops actively reading. This will return in dropped data if it's a live stream.
mpv on the other hand is stream oriented, and does not allow filters to seek. (And it would not make sense to allow it, because it would ruin performance.) Filters get frames sequentially in playback direction, and cannot request them out of order.
Increasing this buffer will not improve performance. Rather, it will waste memory, and slow down seeks (when enough frames to fill the buffer need to be decoded at once). It is only needed to prevent the error described in the previous paragraph.
Note that Z order between different overlays of different formats is static, and cannot be changed (currently, this means that bitmap overlays added by overlay-add are always on top of the ASS overlays added by osd-overlay). In addition, the builtin OSD components are always below any of the custom OSD. (This includes subtitles of any kind as well as text rendered by show-text.)
The end of a seek range is usually smaller than the value returned by the demuxer-cache-time property, because that property returns the guessed buffering amount, while the seek ranges represent the buffered data that can actually be used for cached seeking.
bof-cached indicates whether the seek range with the lowest timestamp points to the beginning of the stream (BOF). This implies you cannot seek before this position at all. eof-cached indicates whether the seek range with the highest timestamp points to the end of the stream (EOF). If both bof-cached and eof-cached are true, and there's only 1 cache range, the entire stream is cached.
fw-bytes is the number of bytes of packets buffered in the range starting from the current decoding position. This is a rough estimate (may not account correctly for various overhead), and stops at the demuxer position (it ignores seek ranges after it). 041b061a72