Grencola wrote: ↑Sat Apr 18, 2020 2:55 am
mike admin wrote: ↑Fri Apr 17, 2020 6:21 pm
Extract Atmos metadata from TrueHD frame, decode TrueHD frame to LPCM, encode LPCM to eac3, add Atmos metadata to eac3 frame.
This can even be done on the fly...
for realz? afaik only this:
https://www.dolby.com/us/en/professiona ... suite.html
can remux thd atmos into dd+ atmos. do you mean you can hex edit your thd file at the NAL level and hot swap bits to circumvent the need for crazy expensive licensed software?
The true answer - I don't know. But, what I "feel" - it should not be too hard. I mean, think of it, atmos is just metadata, and as long we are not changing audio/video configuration (channel layout, sample rate, video fps) then it really doesn't matter what underlying codec is used. Couple points:
1. We all know where exactly atmos metadata is stored in MLP and DDP frames. It only takes someone to compare these frames from the same-content track and see if metadata is the same. My gut feeling it is.
2. Dolby engineering is sort of "straightforward". For years(!!!) we have discussed what a complex job would be to convert DV streams and how million dollar software and NDA specs are required. Outcome? Converting from double-PID to single-PID is a matter of prefixing a single byte per packet. And with Dolby patents released in December 2019 we now know entire DV RPU structure - MakeMKV currently detects MEL and FEL streams, and to do so it parses 90% of RPU unit. It is not
that hard. So, with current knowledge, even the "impossible" task of converting double-layer FEL to single-layer MEL looks quite doable - not as trivial as prefixing a byte, but not an impossible task either - decode EL layer, render data, encode coefficients back with MEL parameters, profit. Code complexity - like any codec, similar to decoding an ac3 frame.
So yeah, I would bet my money that atmos metadata is just a blob that can be taken from MLP frame and inserted into DDP frame, providing frame sizes and channel configuration is the same.