TrueHD vs Dobly Digital from TrueHD downconversion - your opinion

[Alsone]

Hi,

I'm just curious to know what everyone's findings on TrueHD are.

On my Panasonic BD35 and Onkyo 605SR amp after I finally found out how to stream TrueHD (turn the bitstream conversion off on secondary video), I noticed something immediately - it doesn't sound as good as the uncompressed soundtrack down converted and outputed as Bitstream and played back by the amp as Dolby Digital.

My main findings were:

1. Dialogue Louder and Clearer

2. Overall sound much punchier and louder (especially explosions eg fireworks on intro to national treasure 2)

3. Better dynamics

So for me I've reset my amp to Bitstream and I'm using Dolby Digital from the downconverted source.

I was just wondering if anyone else has found DD downconversion from uncompressed better than TrueHD for quality.

 

[professorhat]

Okay, I just wanna check I'm getting this right (as it's a bit muddled above I think). Your two methods above are:
1. Dolby TrueHD bitstreamed from the BD35 to the amp.
2. Dolby Digital bitstreamed from the BD35 to the amp.
Is that right? And you find the Dolby Digital soundtrack is better than the Dolby TrueHD soundtrack? What confuses me is when you say the uncompressed soundtrack which indicates there is a PCM soundtrack on the disc as well? If so, how does this make sense with the above soundtracks?

 

[Alsone]

Edited the original title - even got me confused this.

Yes Dolby True HD is being output as Bitstream.

When the BD35 players Secondary Audio is on, it processes it and outputs it as Dolby Digital.

Now comparing the two back to back ie. True HD vs Dolby Digital processed by the player from the True HD source, I can notice no real difference in audio quality from True HD and in fact the Dolby Digital down conversion sounds better after the players processing than the True HD source in the ways I posted above.

Was just wondering if anyone else has noticed DD downconversion (done in the BD player) sounding better than the True HD source?

Obviously True HD should sound better, it just doesn't seem to work that way.

 

[professorhat]

Yes, very strange - basically the DD core track is removing one hell of a lot of detail from the Dolby TrueHD soundtrack so it's impossible it could be adding anything, only removing detail (like taking a CD track and converting it down to a 128Kbps MP3 file).
I haven't noticed this on any of my films with Dolby TrueHD, the TrueHD soundtrack has always been very noticeably better. Which film is it?

 

[Alsone]

National Treasure 2 - Book of Secrets.

I also noticed more punch with Kung Fu Panda.

I'll perhaps see if I can record the 2 back to back on my camcorder although it doesn't record great sound so don't know if it will show it.

 

[The_Lhc]

Have you tried NOT bitstreaming the TrueHD but decoding it on board and passing that to your amp (as the BD35 can do that, I don't know if your amp can handle that though?), to see how that sounds?

It sounds to me like you're actually getting the opposite of what you think you are, the TrueHD should be more dynamic and punchy, all those things you say the DD is. It's odd whatever!

 

[Alsone]

the_lhc:

Have you tried NOT bitstreaming the TrueHD but decoding it on board and passing that to your amp (as the BD35 can do that, I don't know if your amp can handle that though?), to see how that sounds?

It sounds to me like you're actually getting the opposite of what you think you are, the TrueHD should be more dynamic and punchy, all those things you say the DD is. It's odd whatever!

Hi lhc, thats exactly what the 2nd option does.

The True HD option bitstreams True HD to the amp. The on board option down converts True HD to Dolby Digital then sends it to the amp.

My "problem" is the DD sounds better than the True HD output which basically means a converted True HD sounds better than a pure bitstreamed True HD output. Something that you wouldn't expect to happen.

 

[Alsone]

I now have proof, I'll put the HD video clip up later but here it is pulled into my video editor:

True HD via Bitstream peaks on the Left Hand Side, Dolby Digital downconversion from True HD on the right.

You can immediately see the peaks on the right hand side (the down conversion) are larger and more dynamic.

http://img87.imageshack.us/img87/2500/truehdvsddpeaksja7.jpg

 

[The_Lhc]

Alsone:the_lhc:

Have you tried NOT bitstreaming the TrueHD but decoding it on board and passing that to your amp (as the BD35 can do that, I don't know if your amp can handle that though?), to see how that sounds?

It sounds to me like you're actually getting the opposite of what you think you are, the TrueHD should be more dynamic and punchy, all those things you say the DD is. It's odd whatever!

Hi lhc,

THE lhc...

thats exactly what the 2nd option does.

The True HD option bitstreams True HD to the amp. The on board option down converts True HD to Dolby Digital then sends it to the amp.

My "problem" is the DD sounds better than the True HD output which basically means a converted True HD sounds better than a pure bitstreamed True HD output. Something that you wouldn't expect to happen.

Hmmm, you mentioned something about a "secondary audio" option, can I ask how you've got the BD35 connected to the amp? Just through HDMI or have you connected the optical digital connection as well?

I was going to ask something else but I've forgotten what it is...

 

[The_Lhc]

Oh yeah, you are using a fully 1.3a complaint HDMI cable aren't you? you know the ones with the higher bandwidth that you need to carry both 1080p AND the high bitrate audio?

I'm just looking at the manual for the BD-35 (and 55 it's the same manual). It definitely says if secondary audio is on it'll only output DD or DTS, if secondary audio is off it'll output the HD tracks.

Does it sound any different setting it to PCM?

 

[Alsone]

The secondary audio option is the option in the BD35's set up menu that controls whether or not the player outputs True HD as Bitstream or Dolby Digital (downscaled from True HD).

I've put a screen shot below so you can read what it says but it clearly says that the Dolby Digital is converted from the True HD as opposed to played from the DD on the disc:

http://img356.imageshack.us/img356/253/bitstreamcw7.jpg

 

[Alsone]

Back to back video is up now:

http://vimeo.com/2417407

Not as easy to tell after Flash Conversion but even so, I still think there's some difference to be heard. On the original its even more marked.

Apologies for reflections - video camera pics them up much better than the eye!

 

[kinda]

This seems quite weird.

I wonder if what you're getting is the TrueHD decoded to PCM sent to the amp, which would make more sense from the comparative results, (though I don't know if this is even possible with this player / amp combo).

However, if it's definitely the basic DD track being sent the conclusion has to be that the 605 is much poorer at converting a TrueHD track than DD, which makes sending it high-def a bit pointless. I can't imagine that the player somehow makes the TrueHD rubbish, as it is sending it as is.

 

[Alsone]

When in True HD output mode, the Onkyo amp shows True HD on the display so its obviously receiving True HD.

What I can't understand is having heard that True HD is the holy grail of sound, how DD down converted from True HD in the BD35 can sound so much more dynamic and clearer than True HD sent "as is" to the Onkyo.

Have What Hi Fi tested / come across this?

 

[Anonymous]

Hi, have you tried setting secondary audio to off, then bitstreaming True HD/DTS HD. I have a vague recollection (which may be wrong) that secondary audio is to allow you to hear bonus view stuff, commentaries etc, and that you can't output HD codecs at the same time. I think if you set it to off, then bitstream HD (the red light on your amp will tell you it's receiving this), then you should hear the benefits of HD. I have to say that the difference between HD audio and standard DD/DTS seems pretty unequivocal to my inexpert ears.

Hope it works out for you.

Shuggie

 

[Alsone]

Hey Shruggie,

Thats exactly what I've been doing - bitstreaming the True HD with it set to off.

With it on, the BD35 only puts out downconverted video.

I took a screenshot earlier of the instruction set for this feature:

 

[The_Lhc]

Alsone:
Hey Shruggie,

Thats exactly what I've been doing - bitstreaming the True HD with it set to off.

With it on, the BD35 only puts out downconverted video.

well according to the manual it downmmixes the primary and secondary audio feeds for use with the picture in picture mode for discs that have this content on them.

I took a screenshot earlier of the instruction set for this feature:

I presume this was before you set the secondary audio to "off"?

 

[Alsone]

Secondary Audio On = Down conversion to Dolby Digital

Secondary Audio Off = True HD output to Receiver.

However down converted audio sounds better than True HD and both recordings and Waveform analysis show greater dynamic range.

Any comments What Hi Fi?

It would be really useful to get a professional perspective on this as it has far reaching implications for everyone's settings where Blu Ray discs / players are concerned.

 

[The_Lhc]

Well, it only has implications if EVERY blu-ray player does this, it could simply be that yours is faulty perhaps?

 

[professorhat]

Indeed, certainly with mine, Dolby TrueHD sounds much better than a Dolby Digital core soundtrack (tested thoroughly when I first got my HD audio capable amplifier).

 

[pete321]

I've found TrueHD to sound only marginally better than Dolby Digital 640kbps. Compared to DTS-HD Master and PCM, TrueHD lags quite a long way behind in my opinion.

 

[Alsone]

the_lhc:Well, it only has implications if EVERY blu-ray player does this, it could simply be that yours is faulty perhaps?

Whereas I couldn't rule that out, I see no reason to suspect it. The receiver shows True HD on the display so its obviously getting a True HD signal.

professorhat:
Indeed, certainly with mine, Dolby TrueHD sounds much better than a Dolby Digital core soundtrack (tested thoroughly when I first got my HD audio capable amplifier).

I hear what you're saying Prof but its slightly different here. Its not playing back the DD soundtrack with 2ndary audio set to on, its taking the True HD soundtrack and downconverting it to DD then outputting that (according to my understanding of the screenshot posted above). So what I'm comparing is True HD to Onkyo vs True HD processed in BD35 then outputted to Onkyo as DD.

 

[professorhat]

Yup, that's what I was talking about when I said Dolby Digital core track i.e. the one taken from the Dolby TrueHD signal. Of course I'm using the PS3 so there's a difference there, but as I said, when it's exporting the Dolby Digital core track (and this is any BD player), it's removing detail not adding anything so I fail to see how this can possibly sound better unless something odd is occurring.

 

[Anonymous]

Sorry to bring this old thread up, but found it quite interesting. Reason, i thought true Hd should sound better. However, i have found DTS seems to sound better to my ears. It just seems more clear. Things like speech are a lot easier to hear than that of true hd. Its all very confusing!!!