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Old 18th October 2018, 09:45   #14721  |  Link
sneaker_ger
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This is the link I posted earlier: https://developer.apple.com/library/...TFFAppenG.html
Apple's AAC encoder uses 2112 samples of delay. At 48 kHz that's exactly 44ms. If you use QAAC it confirms this.

(Of course we still can't be 100% sure that's what they use for their streaming but it's the best guess until someone has a properly decrypted sample.)
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Old 18th October 2018, 10:29   #14722  |  Link
sneaker_ger
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Quote:
Originally Posted by sneaker_ger View Post
Quote:
Originally Posted by justnobody View Post
and we demux this file with eac3to and put them (all tracks) together again with mkvtoolnix, delay is gone, 0ms now
If you demux to "raw" (ADTS) AAC there is no way to store the delay infos that mkv or mp4 container can store. It is lost. You will introduce a slight delay (here: -5ms). MediaInfo doesn't know this. It is not an AI that analyzes e.g. speech to mouth movement of video but only looks at the delay values stored in the container (mkv/mp4).
@justnobody
One thing I forgot to add:
When you extract certain audio formats with eac3to it will delete/add audio frames to preserve the delay value of the source container as best as possible (within length of 1 audio frame). The eac3to log should tell you if that happens. Not sure if that works with AAC as eac3to's AAC handling seems to be very limited.
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Old 18th October 2018, 13:43   #14723  |  Link
Dulus_No
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Quote:
Originally Posted by mkver View Post
You are making presumptions about the aac encoder delay that needn't be true. Not every aac encoder has a delay of 2 frames. The best bet would probably to test Apple's AAC encoder. Or maybe Dulus_No knows a bit more about this?
[Edit]: This and this both suggest 2112 samples which are exactly 44ms. You knew that, didn't you?
[Edit2]: Yes, you did. Of course you did.
The same delay shows up not only on AAC tracks but also on AC3 (video has a +42ms / 1 frame delay). mp4dump of original m4v with drm and decrypted with TunesKit m4v.
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Old 18th October 2018, 14:09   #14724  |  Link
sneaker_ger
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Ok, so only one edts/elst with "media time" != 0.
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Old 18th October 2018, 21:20   #14725  |  Link
arrgh
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Originally Posted by sneaker_ger View Post
There are 2 ways to store Dolby Vision. One as SEI messages in the base video stream. On Blu-Ray it seems they use a second "track" instead. As you say there isn't really any way to "properly" copy that into mkv yet.
yes, I see a second Video track...

https://www.bilder-upload.eu/bild-d1...93458.jpg.html

so, that means it is relly a second independant track and not something like a "forced pgs" which sometimes comes as an individual track, sometimes enbedded in a general track where some frames are marked as forced...
or, in other words, the contend of this track is not also included in the first video stream; to maintain the complete data one would need to mux the second track into a container?
there are also no other containers (instead of mkv) which could be used for this and enable rederers like madVR to use the data?

Last edited by arrgh; 18th October 2018 at 21:27.
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Old 18th October 2018, 21:29   #14726  |  Link
sneaker_ger
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I don't know any free software that supports Dolby Vision. (This includes madVR.)
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