Convert TrueHD to FLAC
Dolby TrueHD Logo
TrueHD has very good compression ratio, so multichannel FLAC conversion of both 16 / 24-bit audio soundtracks almost have no impact.
| Saving (Movie / Audio) | Movie Name | TrueHD Size (GB) | FLAC Size (GB) | Saving (GB) | Layout / Bit Depth | Movie Size (GB) |
| 3% / 16% | The Art of Flight (2011) | 3,15 | 2,64 | 0,51 | 7.1 / 24 | 17,82 |
| 1% / 15% | Gone with the Wind (1939) | 2,04 | 1,73 | 0,31 | 5.1 / 16 | 32,01 |
| 1% / 15% | Gandhi (1982) | 1,65 | 1,41 | 0,24 | 5.1 / 16 | 32,33 |
| 1% / 12% | The Last Samurai (2003) | 1,47 | 1,30 | 0,17 | 5.1 / 16 | 19,43 |
| 1% / 10% | The Matrix (1999) | 1,57 | 1,41 | 0,16 | 5.1 / 16 | 17,22 |
| 1% / 9% | The Matrix Revolutions (2003) | 1,63 | 1,48 | 0,15 | 5.1 / 16 | 14,32 |
| 1% / 8% | The Matrix Reloaded (2003) | 1,72 | 1,58 | 0,14 | 5.1 / 16 | 15,13 |
| 1% / 6% | Event Horizon (1997) | 2,31 | 2,16 | 0,15 | 5.1 / 24 | 26,63 |
| 1% / 6% | How to Train Your Dragon (2010) | 2,37 | 2,22 | 0,15 | 7.1 / 24 | 17,49 |
| 0% / 4% | Kung Fu Panda 2 (2011) | 2,27 | 2,18 | 0,09 | 7.1 / 24 | 18,70 |
| 1% / 10% | Total | 20,18 | 18,11 | 2,07 | 211,08 |
The one issue with TrueHD is that information about the actual bitdepth is not contained anywhere in the TrueHD track. In result 24 bit value is used by default. To verify true bit depth additonal eac3to tool was used. This software is the swiss army knife in audio processing. People that are really picky about perfect rips/remuxes, recommend using software that use eac3to to demux the blu-ray and convert lossless audio to FLAC.
eac3to CLI
Since the bit-depth is simply not known before the processing, eac3to has no other choice than to fully decode the full track and check the bit-depth of every single audio sample (of which there are usually 48000 for every second of the runtime). If all 24-bit audio samples have trailing 8 bits zeroed out, eac3to will state that it's a 16-bit track and trim zeros out without quality loss. eac3to output will look like the following in such case:
[a04] The original audio track has a constant bit depth of 16 bits. [a04] Superfluous zero bytes detected, will be stripped in 2nd pass. [a04] Reducing depth from 24 to 16 bits...
The size difference of 24-bit and 16-bit FLAC files converted with MakeMKV (via FFmpeg) and eac3to accordingly, was insignificant and equals to few megabytes only. Which means that latest versions of FLAC compressing fake zeroed out bits perfectly.