Smooth Streaming Support : TTML Captions #1878
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| @@ -326,7 +330,10 @@ function TextSourceBuffer() { | |||
| subOffset += sample.subSizes[j]; | |||
| } | |||
| try { | |||
| result = parser.parse(ccContent, sampleStart / timescale, (sampleStart + sample.duration) / timescale, images); | |||
| // check if we must apply an offset to ttml time | |||
| let manifest = manifestModel.getValue(); | |||
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Please add a comment here that MSS has an offset corresponding to the segment start, while DASH has none.
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This is definitely a bug, since the MSS time intervals will be off without the fix. The code looks fine, but I think it is essential to point out that the offset parameter is there only to support MSS, so that there is no-one thinking that it can be used for DASH as well. |
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Hi Went on holidays last week ;-) |
- Display TTML on smooth streaming streams
- Update comment
jeremco
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@dsparacio The code climate check is not helpful here since it complains that we declare the same variables in multiple files. How can we suppress the failing check? |
Is this consistent with the following prose in ISO 14496-30? The top-level internal timing values in the timed text samples based on TTML express times on the track |
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If I understand correctly @palemieux the constraints of ISO 14496-30 do not necessarily apply to Smooth streams. Regardless of whether that is correct according to the spec for Smooth, all the TTML in Smooth that I have seen has fragment-relative times. |
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@jeremco Can you add a subtitled Smooth test asset to the reference player so that we have a way of checking that this patch works, and so that we can also make sure it works when integration imsc1JS? |
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@palemieux Smooth does not follow ISO 14496-30, so one needs different timing in TTML for MSS vs DASH. |
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Ok. Thanks for clarifying. See proposal at #1693 (comment) |
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@TobbeEdgeware, if you activate MSS in dash, the first sample ('Prince of Persia') has subtitles. |
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@jeremco I checked the MSS source you mentioned, and the French subtitles work, while the English don't. Anyway, I think this is good, so I'll merge this. We then need to carry over this to the imscJS1 integration in #1693. Instead of sending an offset to TTMLParser, I think that we should send the flag ttmlTimeIsRelative, since that code becomes simpler and the ttmlTimeIsRelative flag fits nicely into the calculations of startTime and stopTime |
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I agree wih you @TobbeEdgeware. Thanks for the merge. I have checked for english subtitles. Actually, I think they work, but the subtitles are not from Prince of Persia, and they still are written in french ;-) This is a test stream |
Hello
The goal of this PR is to fix a pb on Smooth Streaming subtitles.
The TTML begin and end tags are absolute. But in this case they are relative to fragments start time.