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[Session] Implement inputstream times interface for live streams - #2130
Implements the inputstream times interface (GetTimes, INPUTSTREAM_SUPPORTS_ITIME) for live streams.
INPUTSTREAM_SUPPORTS_ITIME is only set for live streams, VOD is not affected.
ptsStart is the PTS of the elapsed time 0, i.e. the inverse of PTSToElapsed. This reintroduces the logic of GetTimeshiftBufferStart (removed as unused in 88bd6fd), now with a user. ptsBegin is ptsStart.
startTime (wall clock time of ptsStart) is based on an offset between PTS and the local clock. It is determined once per period in GetNextSample, when the first sample of the timing stream is read, assuming that the end of the timeline is the live position. The offset is reset in InitializePeriod.
ptsEnd is the live position minus the live delay, derived from the same offset. The end of the seekable range therefore advances in real time, also while no segments are read (e.g. paused). It is never before ptsStart.
Times are only provided for single-period streams, as the PTS of different periods are not necessarily continuous. For multi-period streams, and until the offset is known, GetTimes returns false and Kodi uses the display time as before.
No changes to the Kodi API or Kodi core are required.
Motivation and context
The PVR timeshift UI in Kodi (CPVRGUITimesInfo) relies on the inputstream times. Without them, for live TV played with inputstream.adaptive:
the OSD (EPG event elapsed time, timeshift progress) always shows the live position, also after seeking;
clicking the timeshift seek bar (PVR.SeekPercentage) seeks to the start of the timeshift buffer, because without a start time the stream is treated as not timeshifting and the buffer start is placed at the current time, so the seek target is clamped to 0.
Relates to #154, where ksooo mentioned that the inputstream implementing the times interface is a precondition for the timeshift UI. #154 also mentions that a previous attempt did not work well with VideoPlayer. Here ptsStart is chosen so that CVideoPlayer::UpdatePlayState calculates the same time and time_offset as with the display time. PosTime, subtitle timing and trickplay therefore work as before; only the start time and the seekable range are added.
Notes for review
Wall clock time: not all manifest types provide it (EXT-X-PROGRAM-DATE-TIME is optional in HLS, Smooth Streaming has none, and for DASH it would depend on the PTO handling, see the @todo in DASHTree.cpp). Kodi also uses the local clock for "now" and the EPG. In my tests the PTS of the streams correspond to the wall clock time, so the logged offset is the deviation: 1.3–6.7 s. Using the manifest wall clock time where available could be a follow-up.
Sliding windows:ptsStart deliberately stays the PTS of the elapsed time 0 as used by PosTime, i.e. based on GetAbsolutePTSOffset(), which is updated when the next segment is read. VideoPlayer passes seek times relative to ptsStart to PosTime, and SeekTime adds GetAbsolutePTSOffset(), so deriving ptsStart from the current window would shift every seek by the amount the window has moved. While no segments are read, the begin of the range stays at the last read window start, like with the display time; the end advances (see ptsEnd).
Threading: the offset is set in GetNextSample and read in GetTimes, both on the VideoPlayer thread, which also calls DemuxRead and PosTime (GetNextSample and PosTime log the same thread ID). m_totalTime is read in the same way as in GetTotalTimeMs. No locks are taken.
Side effects in Kodi core when a stream provides a start time: VideoPlayer stores no resume position on close (it only does so if startTime == 0), and Player.StartTime returns the stream start time. This only applies to live streams.
How has this been tested?
Kodi 22.0-RC1 (Git:20261017-f09bcd5ac4), Linux x86-64, Estuary. inputstream.adaptive Piers (da3e519) with this patch. Live TV via pvr.waipu (DASH, single period), partly with a local pvr.waipu change that requests the live stream from the start of the current programme (growing timeshift window covering the programme, playback starts at the live position), partly without it (normal live stream with a sliding timeshift window of about 2 minutes).
Before (unpatched v22.3.23): nearly every click on the timeshift seek bar resulted in demuxer seek to: 0.000000. Seeking with the arrow keys worked, but the OSD kept showing the live position.
Current version:
Growing window (SAT.1): 5/5 seek bar clicks succeeded. After a pause of about 45 s, seeking close to the live position worked.
EPG tag playback from programme start (phoenix): times provided, 2/2 seeks succeeded.
Sliding window (SAT.1 without the local pvr.waipu change): 4/4 seeks succeeded. While the window moved, ISA still used the previous window start until the next segment was read (Seek time 0.0 ... continues at 2.9), which is why ptsStart follows GetAbsolutePTSOffset() (see notes above).
Pause with a sliding window (SAT.1 without the local pvr.waipu change, two runs of about 37 s and 25 s): manifest updates continued while no segments were read, the offset to the live position kept growing in the OSD, and seeking during the pause and after resuming worked.
VOD (waipu recording, Type: VOD): no times provided, resuming via PosTime (11423000) worked.
Earlier versions (same ptsStart and startTime, but ptsEnd was ptsStart plus GetTotalTimeMs()):
Offset set in GetNextSample (Das Erste, SAT.1, tagesschau24, ZDFneo): 5/5 seek bar clicks landed at the clicked position (e.g. PosTime (188906), PosTime (69374), PosTime (318080)), the OSD elapsed time follows the play position.
Offset set on the first GetTimes call (WELT, Das Erste, about 20 minutes): 40/40 seeks via seek bar and arrow keys succeeded. A click beyond the live edge (PosTime (2400000)) was clamped by the existing SeekTime logic.
No new compiler warnings (GCC, -Wall -Wextra), changed lines formatted with clang-format.
Not tested yet: HLS and Smooth Streaming live, multi-period live, live streams outside of PVR (video add-ons), other platforms.
Screenshots (if appropriate):
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My change requires a change to the Wiki documentation
I have updated the documentation accordingly
Summary by CodeRabbit
New Features
Live streams can now provide start-time and playback-timing information to compatible media players. This helps playback interfaces display live timing details when the stream has the required timing data: a single chapter and an available start time. The reported seekable range follows the live edge, accounting for live delay, and does not extend before the stream’s start. When the required timing data is unavailable or incomplete, live timing information is not provided.
No actionable comments were generated in the recent review.
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src/Session.cpp
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Walkthrough
The session now calculates live-stream PTS and wall-clock timing values. The inputstream advertises timing support for live sessions and exposes those values through GetTimes.
The session stores and resets a PTS-to-wall-clock offset. It derives the timing stream start PTS and returns live timing values when the stream has one chapter, the offset is available, and the timing reader has a valid start PTS.
Inputstream timing API src/main.h, src/main.cpp
The inputstream advertises INPUTSTREAM_SUPPORTS_ITIME for live sessions. Its GetTimes method returns false when timing values are unavailable; otherwise, it populates the start time and PTS range.
Live timing may show a range beyond available media for some DASH manifests, but seeking is clamped. This is a bounded issue that can be accepted or followed up without blocking merge.
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The title clearly and concisely identifies the main change: implementing the inputstream times interface for live streams.
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Write docstrings for the functions missing them to satisfy the coverage threshold.
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Actionable comments posted: 1
🪄 Fix comments: Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @src/Session.cpp:
- Around line 824-825: Update the PTS calculation using m_timingStream and
timingReader so the start PTS comes from the current DASH timeline window rather
than the last consumed segment’s cached GetAbsolutePTSOffset value. Read the
current timeline start under the tree update lock, or refresh the cached start
when the timeline changes, while preserving the existing PTS-difference
calculation.
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src/Session.cpp
src/Session.h
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Kodi PVR requires the inputstream times to show the timeshift progress
and play position of live channels, and to seek on the timeshift seek
bar. Without them the PVR OSD always shows the live position, and
seeking on the seek bar jumps to the start of the timeshift buffer
(see xbmc#154).
Provide the times for live streams with a single period. The start PTS
is the PTS of the elapsed time 0, so the time calculated by Kodi
matches the display time and PosTime. As not all manifest types
provide the wall clock time, the start time is calculated assuming that
the end of the timeline is the live position. The offset between PTS
and wall clock time is determined once per period when the first sample
of the timing stream is read, as PTS values increase in real time. The
end of the seekable range is derived from the same offset, so it also
advances while no segments are read, e.g. while paused.
Multi-period streams are excluded, as the PTS of different periods are
not necessarily continuous.
Absolutely understandable. So far I have only runtime-tested it on my own setup and it has been working well there. I have added two screenshots to the description.
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Description
Implements the inputstream times interface (
GetTimes,INPUTSTREAM_SUPPORTS_ITIME) for live streams.INPUTSTREAM_SUPPORTS_ITIMEis only set for live streams, VOD is not affected.ptsStartis the PTS of the elapsed time 0, i.e. the inverse ofPTSToElapsed. This reintroduces the logic ofGetTimeshiftBufferStart(removed as unused in 88bd6fd), now with a user.ptsBeginisptsStart.startTime(wall clock time ofptsStart) is based on an offset between PTS and the local clock. It is determined once per period inGetNextSample, when the first sample of the timing stream is read, assuming that the end of the timeline is the live position. The offset is reset inInitializePeriod.ptsEndis the live position minus the live delay, derived from the same offset. The end of the seekable range therefore advances in real time, also while no segments are read (e.g. paused). It is never beforeptsStart.GetTimesreturns false and Kodi uses the display time as before.No changes to the Kodi API or Kodi core are required.
Motivation and context
The PVR timeshift UI in Kodi (
CPVRGUITimesInfo) relies on the inputstream times. Without them, for live TV played with inputstream.adaptive:PVR.SeekPercentage) seeks to the start of the timeshift buffer, because without a start time the stream is treated as not timeshifting and the buffer start is placed at the current time, so the seek target is clamped to 0.Relates to #154, where ksooo mentioned that the inputstream implementing the times interface is a precondition for the timeshift UI. #154 also mentions that a previous attempt did not work well with VideoPlayer. Here
ptsStartis chosen so thatCVideoPlayer::UpdatePlayStatecalculates the sametimeandtime_offsetas with the display time.PosTime, subtitle timing and trickplay therefore work as before; only the start time and the seekable range are added.Notes for review
EXT-X-PROGRAM-DATE-TIMEis optional in HLS, Smooth Streaming has none, and for DASH it would depend on the PTO handling, see the@todoinDASHTree.cpp). Kodi also uses the local clock for "now" and the EPG. In my tests the PTS of the streams correspond to the wall clock time, so the logged offset is the deviation: 1.3–6.7 s. Using the manifest wall clock time where available could be a follow-up.ptsStartdeliberately stays the PTS of the elapsed time 0 as used byPosTime, i.e. based onGetAbsolutePTSOffset(), which is updated when the next segment is read. VideoPlayer passes seek times relative toptsStarttoPosTime, andSeekTimeaddsGetAbsolutePTSOffset(), so derivingptsStartfrom the current window would shift every seek by the amount the window has moved. While no segments are read, the begin of the range stays at the last read window start, like with the display time; the end advances (seeptsEnd).GetNextSampleand read inGetTimes, both on the VideoPlayer thread, which also callsDemuxReadandPosTime(GetNextSampleandPosTimelog the same thread ID).m_totalTimeis read in the same way as inGetTotalTimeMs. No locks are taken.startTime == 0), andPlayer.StartTimereturns the stream start time. This only applies to live streams.How has this been tested?
Kodi 22.0-RC1 (Git:20261017-f09bcd5ac4), Linux x86-64, Estuary. inputstream.adaptive
Piers(da3e519) with this patch. Live TV via pvr.waipu (DASH, single period), partly with a local pvr.waipu change that requests the live stream from the start of the current programme (growing timeshift window covering the programme, playback starts at the live position), partly without it (normal live stream with a sliding timeshift window of about 2 minutes).demuxer seek to: 0.000000. Seeking with the arrow keys worked, but the OSD kept showing the live position.Seek time 0.0 ... continues at 2.9), which is whyptsStartfollowsGetAbsolutePTSOffset()(see notes above).Type: VOD): no times provided, resuming viaPosTime (11423000)worked.ptsStartandstartTime, butptsEndwasptsStartplusGetTotalTimeMs()):GetNextSample(Das Erste, SAT.1, tagesschau24, ZDFneo): 5/5 seek bar clicks landed at the clicked position (e.g.PosTime (188906),PosTime (69374),PosTime (318080)), the OSD elapsed time follows the play position.GetTimescall (WELT, Das Erste, about 20 minutes): 40/40 seeks via seek bar and arrow keys succeeded. A click beyond the live edge (PosTime (2400000)) was clamped by the existingSeekTimelogic.-Wall -Wextra), changed lines formatted with clang-format.Not tested yet: HLS and Smooth Streaming live, multi-period live, live streams outside of PVR (video add-ons), other platforms.
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Summary by CodeRabbit