From 2a83c42e0c8024b3668a497e0f916fa29338d992 Mon Sep 17 00:00:00 2001 From: rcombs Date: Sat, 27 Mar 2021 21:15:31 -0500 Subject: [PATCH 1/2] Clarify that TrackOverlay links by UID (not Number) --- ebml_matroska.xml | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/ebml_matroska.xml b/ebml_matroska.xml index 0e3e0688..45996492 100644 --- a/ebml_matroska.xml +++ b/ebml_matroska.xml @@ -448,7 +448,7 @@ see [@!I-D.ietf-cellar-codec] for more info. - Specify that this track is an overlay track for the Track specified (in the u-integer). + Specify that this track is an overlay track for the Track UID specified (in the u-integer). That means when this track has a gap, see (#silenttracks-element) on SilentTracks, the overlay track **SHOULD** be used instead. The order of multiple TrackOverlay matters, the first one is the one that **SHOULD** be used. If not found it **SHOULD** be the second, etc. From 86e0acc492128d1f4febae583007df78519d17bf Mon Sep 17 00:00:00 2001 From: rcombs Date: Thu, 31 Dec 2020 20:27:09 -0600 Subject: [PATCH 2/2] Add subtitle->audio track linking --- ebml_matroska.xml | 6 ++++++ notes.md | 21 +++++++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/ebml_matroska.xml b/ebml_matroska.xml index 45996492..3ca99985 100644 --- a/ebml_matroska.xml +++ b/ebml_matroska.xml @@ -454,6 +454,12 @@ the overlay track **SHOULD** be used instead. The order of multiple TrackOverlay If not found it **SHOULD** be the second, etc. + + Specify that subtitle track is suitable for use with the audio Track UID specified (in the u-integer). +Multiple subtitle tracks may link to the same audio track, and the same subtitle track may link to multiple audio tracks by providing multiple TrackLink elements. + + + CodecDelay is The codec-built-in delay in nanoseconds. This value **MUST** be subtracted from each block timestamp in order to get the actual timestamp. diff --git a/notes.md b/notes.md index 536832d7..51d0109a 100644 --- a/notes.md +++ b/notes.md @@ -327,6 +327,27 @@ Overlay tracks **SHOULD** be rendered in the same channel as the track its linke When content is found in such a track, it **SHOULD** be played on the rendering channel instead of the original track. +## Track Links + +A track link indicates that a given subtitle track is suitable for use with a given audio track, +and that it **SHOULD** be eligible for autoselection when that audio track is selected. + +For instance: +- A subtitle track containing a translation of an audio track in another language should be + linked to that track, but should not be linked to another audio track featuring a dub + into the same language with a different translation. + A subtitle track containing a transcription of the dub, if present, should be linked to the dub audio track. +- A forced subtitle track containing onscreen text consistent with the dialogue in an audio track + of the same language should be linked to that track, but should not be linked to another audio track + featuring a different translation into the same language. +- A subtitle track containing a transcription of an audio commentary track should be linked to + that audio commentary track, but not to other tracks featuring separate commentary recordings. + +Track links are only necessary when the set of tracks available creates ambiguity about which +subtitles are appropriate for which audio, and function as a hint to the player to improve +its automatic track selection behavior. In cases where there is no such ambiguity, there is +no need to explicitly specify track links. + ## Multi-planar and 3D videos There are two different ways to compress 3D videos: have each eye track in a separate track