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Re: Dolby TrueHD and DTS Master HD question
BlueJays1 #265690 07/08/09 05:36 PM
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Agreed about the lossless... The clarity and detail is outstanding.

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Re: Dolby TrueHD and DTS Master HD question
ClubNeon #265691 07/08/09 05:46 PM
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 Originally Posted By: ClubNeon
 Originally Posted By: Foobarred
All that being said, I don't know why studios don't just go LPCM everywhere? Why even bother with DTS-HD MA or TrueHD? Same end results and with the storage capacity of BD it's not like space is an issue...

Storage capacity is only part of the issue. The bigger factor is the maximum allowed bitrate of a BD is 36 megabit/sec. A 7.1, 48 kHz, 24-bit PCM track takes over 9 Mbps by itself. Adding multiple languages would quickly use up all the available bandwidth, leaving nothing for the video or subtitle tracks. Dolby's and DTS's lossless compression can easily achieve a 25% reduction, and routinely exceed 50%.


I don't think that would be an issue until ou get to >8 channel audio.

BD drives read at a 1x speed of 36 Mbps, but the BD spec allows for AV rates of up to 48 Mbps. Of that video can be a maximum of 40 Mbps. 8 channel LPCM audio at 16-bit/48khz only requires 6.144 Mbps. There's still the full 40 Mbps of available AV b/w for video.

Even at the 36 Mbps read rate it still leaves ~30 Mbps which is still more than enough to encode very high-quality HD level 1080 AVC or VC-1. In fact, The Dark Knight, with its outstanding video quality is encoded at an average rate of 24 Mbps. I haven't checked but I don't think it even peaks near 30 Mbps.

Also, multiple audio streams shouldn't affect this since you only play one stream at a time.

I agree that the lossless compression options give the disc producer a lot more headroom and freedom with the bandwidth, but from a practical perspective it doesn't seem to be a real problem today and an easy way to save on additional licensing fees during production.

A much better way to address this long term would be for players to read at greater than the 1x speed (36 mbps) so that they could fully utilize the full BD AV bandwidth of 48 mbps....

Re: Dolby TrueHD and DTS Master HD question
Foobarred #265692 07/08/09 06:15 PM
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 Originally Posted By: Foobarred
Also, multiple audio streams shouldn't affect this since you only play one stream at a time.
...
A much better way to address this long term would be for players to read at greater than the 1x speed (36 mbps) so that they could fully utilize the full BD AV bandwidth of 48 mbps....

Multiple audio streams do have an effect, because they are multiplexed in together. The player has to read the container at the mux rate and then extract the parts which it currently needs, ignoring the rest. It's done this way so A/V sync is easy to maintain and there's no seeking required to pull the video from one location on the disc and the audio from another.

Also, no one is going to use less than 20 bits per sample for a feature presentation. With the way PCM is stored that still takes 3 bytes (24-bits). Compression (both lossy and lossless) can pack multiple samples together to recover the wasted 4 bits.

The 48 Mbps allows for buffered data to burst above the 36 Mbps transfer rate of the drive. But the long term average bitrate can never exceed 36 Mbps without creating a new non-backward compatible format, as all the old players with the 1x drives couldn't play the disc correctly.


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Re: Dolby TrueHD and DTS Master HD question
JohnK #265716 07/09/09 02:30 AM
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Individual discs can of course vary in the quality of audio processing given, and impressions gained in casual listening may differ from reality. Note again the results from controlled tests, blind and otherwise, in HomeEntertainment Magazine which have been cited here a couple times before.


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Re: Dolby TrueHD and DTS Master HD question
JohnK #265962 07/12/09 06:42 PM
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Wow, DTS studio's don't sink nearly as much money into their audio playback equipment as Dolby does, that's forsure. I'm glad I read that article though, because I've been under the impression that the TrueHD and MasterAudio formats were both uncompressed. I didn't realize they were still compressed and then uncompressed without loosing an information. I guess I should have figured that when they call it 'lossless' technology.

But I wonder, if a BluRay disc already has an uncompressed PCM track on it, why would they also then try to squeeze either a TrueHD or MasterAudio track on it as well? Isn't that just a bit of overkill?


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Re: Dolby TrueHD and DTS Master HD question
Micah #265964 07/12/09 07:05 PM
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Most newly released BDs no longer use an uncompessed PCM track. It was mostly a stop-gap measure to allow lossless audio while Dolby and DTS were putting the finishing touches on their formats.

I don't know of any which used both PCM and another lossless. Heck, I don't know of any which use both competing lossless compression formats at the same time.


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Re: Dolby TrueHD and DTS Master HD question
ClubNeon #265965 07/12/09 07:25 PM
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Superbad has both TrueHD and PCM. I'm sure there are others.

Re: Dolby TrueHD and DTS Master HD question
CV #265983 07/13/09 03:13 AM
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Ok I'm still confused... if they can put an uncompressed track on a BD then why even bother with TrueHD and MasterAudio at all? Space saving measure? It seems to me that the uncompressed track would be the best possible soundtrack to listen to, so TrueHD and MasterAudio, as good as they are, are a step backwards aren't they?

Not that any of us will ever be able to tell the difference, but I guess if I had my druthers I'd rather just have the uncompressed soundtrack and say screw the rest of the choices.


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Re: Dolby TrueHD and DTS Master HD question
Micah #265984 07/13/09 03:22 AM
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I have no opinion one way or the other on lossless versus uncompressed. I'd rather they utilize the compression if it allows for higher-quality video. If the format could handle 5 hours of uncompressed video and audio, I'd be all for that, but I wonder how noticeable the difference would actually be. The best stuff on Blu-ray looks and sounds amazing. To see any major improvements will take a new format, and on the audio side, how much better can it actually get?

Re: Dolby TrueHD and DTS Master HD question
Micah #265985 07/13/09 03:51 AM
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Yeah Micah, THD and MHD take up about half the space in their compressed form as the uncompressed PCM does, so there's some space saved that can be used for other video or audio purposes.

You're still not fully grasping the fact that the uncompressed PCM and the two loss-less compressed formats give exactly the same result: a bit-for-bit identical reproduction of the master recording. So, none of the three is any better as a format, and it's up to the producers of the recording how good a job they do with whichever they choose to use.

Of course, there's been quite a bit of hype about what really isn't a very big deal and it should be remembered that we've had a format around for quite a while that has provided uncompressed audio: the CD.


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