TrueHD to PCM / DTS-HDMA not the same

[Bigmango]

Hi,

It seems TrueHD and PCM are not equal after all.

I am trying to convert the Transformers 3 TrueHD track to DTS-HDMA (eac3to + DTS HD Encoder Suite).

The resulting DTS-HDMA track is not the same. Some sounds have less emphasis (for example the intro voice is stronger, more defined compared to the environmental sounds with the TrueHD track). When converted to PCM and DTS-HDMA these sounds which are emphasized in the TrueHD track sound muffled as they get lost in the environmental sounds.

The only explanation I find is that TrueHD applies effects like dialnorm and DRC. So while this doesn't change the compressed PCM contained within the TrueHD track, the decoders (Hardware receiver or PowerDVD) will modify the output by applying these effects on the different channels (as per the meta data contained in the TrueHD track).

So the TrueHD output is different.

Question: is it possible to convert the TrueHD track to DTS-HDMA that will playback the same sound?

[G_M_C]

THD -> EAC3to (remove dialnorm etc. see help for switches) -> MC PCM -> DTS MA should work.

But i dont know the DTS suite, maybe there are some options / switches in there you need to adress ?

[tebasuna51]

Originally Posted by Bigmango

...The only explanation I find is that TrueHD applies effects like dialnorm and DRC.

Then adjust your player to don't apply DRC (dialnorm only change the volume)

[Bigmango]

The problem seems to be the DRC in TrueHD. PCM and DTS-HDMA don't have the meta data to apply these effects on the sound.

It seems the people who think TrueHD and PCM/DTS-HDMA are equal are wrong.

Quote form wikipedia:

Dolby TrueHD bitstreams carry program metadata. Metadata is separate from the coding format and compressed audio samples, but stores relevant information about the audio waveform. For example, dialog normalization and dynamic range compression are controlled by metadata embedded in the TrueHD bitstream.

So, the source lossless sound is modified when decoded; the audio engineers are giving more presence to the different channels depending on the situations, which results in a more dynamic sound.

This is the first time I see this (Transformers 3). Someone tells me Iron Man is also doing this (?).

Question: how can I extract the TrueHD to PCM (wav) with the DRC applied? (I see no setting in eac3to).

(Furthermore, the open source decoders don't seem to be decoding this properly; I don't seem to hear a difference between the original TrueHD and my DTS-HDMA encode when playing back on Media Player Classic HC (needs further testing). But with PowerDVD 12 the difference is there: the TrueHD track is better).

Thanks.

[Bigmango]

Originally Posted by tebasuna51

Then adjust your player to don't apply DRC (dialnorm only change the volume)

The problem is the sound is more enjoyable (more dynamic) with the DRC applied. It makes the movie experience better (and this is how the audio engineers and the director wanted it. So I want to experience the movie as it was meant to).

PowerDVD does it right. The open source decoders don't seem to do this properly (?).

Does anyone know how I can extract the whole sound (including DRC) to keep the TrueHD experience?

[tebasuna51]

Originally Posted by Bigmango

The problem is the sound is more enjoyable (more dynamic) with the DRC applied. It makes the movie experience better (and this is how the audio engineers and the director wanted it. So I want to experience the movie as it was meant to)...

Sorry but that is not true.

Dynamic Range Compression make the audio less dynamic and is only recommended to listen the audio in difficult ambiences (problems with neighborg, children sleeping, car, ...)

Like modern receivers have already a equivalent filter, Night mode, that can be applied to all audio not only AC3/TrueHD, the use of DRC became obsolete.

[rik1138]

Originally Posted by Bigmango

The problem is the sound is more enjoyable (more dynamic) with the DRC applied. It makes the movie experience better (and this is how the audio engineers and the director wanted it. So I want to experience the movie as it was meant to).

This has nothing to do with the audio engineers... The Audio engineers deliver to the studio uncompressed audio. The facility that makes the Blu-ray disc then encodes it either TrueHD or DTSHD-MA. I'd be willing to bet that most times the default settings are used on either encoder. DTSHD's default settings are to do nothing to the audio, play it back exactly as delivered. TrueHD default settings have DialNorm and DRC applied (at least, it used to, I assume it still does... Haven't used it in years). And even if that's not the default settings, they wouldn't be turned on by instruction from the audio designers, but what the person operating the audio compression thinks sounds best. The audio engineers have no idea what sound format is going to be used when they are mixing the film.

Look at the names of the format:
DTSHD-MA. MA = Master Audio, it's meant to be a perfect copy of the original master tapes (or whatever format) delivered from the studio (I believe you can trigger things like normalization and such in DTS, but even DTS themselves don't recommend it. They are of the opinion that the audio should be left alone, as mixed by audio engineers hired by the studio).
TrueHD still likes to tweak things since Dolby has always done that since the days of AC3 on DVD (and probably earlier), so people with Dolby setups expect it...

This causes problems with people these days that have one system that does both formats and either don't, or can't, adjust levels separately for each format. The same audio encoded in both formats will sound different. It _shouldn't_, but many people find that it does... And, naturally, they prefer one over the other and complain about it...

[Bigmango]

@ rik1138: Thanks for the clarifications

Originally Posted by tebasuna51

Sorry but that is not true.

Dynamic Range Compression make the audio less dynamic and is only recommended to listen the audio in difficult ambiences (problems with neighborg, children sleeping, car, ...)

Like modern receivers have already a equivalent filter, Night mode, that can be applied to all audio not only AC3/TrueHD, the use of DRC became obsolete.

Ok, so it maybe something else that's applied to the sound at decoding time; perhaps something like "multiband compression" (=can give some control over specific instruments in a mix) or something else. Hopefully a specialist here can put the right word on what's happening.

=> What I experience with the eac3to extracted lossless Transformers 3 source is that at some times there's so much going on (explosions, movements, etc...) that the sound becomes a "flat mess" (it's badly worded I know, but I think you get what I mean). When this happens, the TrueHD track will give some more presence to specific sounds (For example actions with explosions all over are going on, and suddenly a sports car passes by and it's sound will become more defined - this makes the sound more dynamic and doesn't happen with the extracted source).

So far, the open source decoders (libav, MPC,...) don't seem to be able to decode these TrueHD tracks correctly (they only play the lossless source without the added effects).

PowerDVD 12 plays them fine, but it only outputs 16bit (the TF3 track is 24bit).

Does anyone know of a tool that will allow me to save the TrueHD track to wavs with the TrueHD effects applied?

Thanks for the feedback.

[Qaq]

Originally Posted by Bigmango

Does anyone know of a tool that will allow me to save the TrueHD track to wavs with the TrueHD effects applied?

http://forum.doom9.org/showpost.php?...85&postcount=1

-keepDialnorm disables dialog normalization removal (not recommended)

[tebasuna51]

Originally Posted by Bigmango

...
=> What I experience with the eac3to extracted lossless Transformers 3 source is that at some times there's so much going on (explosions, movements, etc...) that the sound becomes a "flat mess" (it's badly worded I know, but I think you get what I mean). When this happens, the TrueHD track will give some more presence to specific sounds (For example actions with explosions all over are going on, and suddenly a sports car passes by and it's sound will become more defined - this makes the sound more dynamic and doesn't happen with the extracted source).

Don't exist other 'effects' than DialNorm and DRC.

1) DialNorm is not a problem for quality, is only a global attenuation (-4 dB most the times) and can be compensate with the volume control.

2) Dynamic Range Compression work attenuating high volumes (until -20 dB sometimes), then low volumes are more audibles (dialogs, the sport car, ...).
Don't exist: "multiband compression" (=can give some control over specific instruments in a mix) or something else.
But audio engineers don't want so, they want explosions with full volume.

BTW, you are free to save the original TrueHD audio.

I can't recommend recode TrueHD applying DRC, this is a lossy conversion, you can't recover the original audio data. If you apply DRC you losse much more than 24 -> 16 bits precission.