Axiom Home Page Forums General Discussion Home Theater Finally heard uncompressed 5.1 PCM

Mike,
Thanks for the explanation, I guess I'll have to wait for future upgrades to hear DTS-HD

Over the weekend I exchange my Poineer 1017 for a Yamaha 6190 which is the same as the Yammy 1800. Its full 1.3 HDMI.
I did the test with Spiderman BD on a PS3 and flip back and forth from bitstream DD 5.1 vs DD True HD vs 5.1 Uncompressed PCM.
Bitstream DD 5.1 was about 3db higher than the other 2 sources.
Quality is as it was in DD mode. What we have all been used to this past couple of years.
Switching to DD True HD the sound was 3db lower so I raised the volume and use my SPL meter and made sure I was listening the same DB. There was definitely lots of more nuance detail on each sound activity. I know this is subjective but it had a plethora of information which I was not aware about with the same track in DD 5.1.
I switch also to uncompressed 5.1 PCM and it was only a tad bit louder about .5 a db if at all. But sound quality at least to my ears were pretty much the same. I couldnt tell the difference much but I do always leave it at uncompressed 5.1 PCM.
Yammy also has some cool features like presence channel which add to the ambiance in the front so I have pretty much my main 2 speakers (+phantom center from main speaker) and 2 more presence speakers and the front sound stage is seamless and huge. The detail in the 4 speakers I have in front for HT is almost similar to what I get in critical 2 channel listening.
Still waiing in the new year for prices to drop for 1080p projectors or just cheap it out with a Benq W500.

Not just pretty much identical but in theory they should be bit-for-bit identical with absolutely no measurable difference all the way down to the last zero or one. But to know for certain we'd have to know that the compression process didn't do anything other than simply compress the audio, that the decompression similarly didn't apply any adjustments, and that the playback system treated both uncompressed and compressed audio in a similar manner. I'm not 100% confident that any of those three conditions are actually met in the real world.

Some information based on searches:

Dolby TrueHD is Dolby’s next-generation lossless technology developed for high-definition disc-based media. Dolby TrueHD delivers tantalizing sound that is bit-for-bit identical to the studio master, unlocking the true high-definition entertainment experience on next-generation discs
Features
-100 percent lossless coding technology.
-Up to 18 Mbps bit rate.
-Supports up to eight full-range channels of 24-bit/96 kHz audio

The new audio CODECs are lossless which simply means without loss, or identical to the original. The three lossless CODECs supported by both formats are LPCM(not really a codec), Dolby TrueHD and DTS HD MA. At this point the question should be, if they are lossless than what is the difference? The difference for the most part is the number of bits. Both Dolby TrueHD and DTS HD use far less bits than LPCM, this leaves more space on the disc for other features.

So how many bits are we talking about here. As an example a 2 hour movie with a 16/24, 5.1 sound track requires 4.14 GB with LPCM vs 1.26 GB for either TrueHD or DTS HD.

LPCM is not being used at higher than 48kHz sampling rate because of the datarate/storage that would require.

Dolby TrueHD definitely supports higher sampling rates than 48k

Uncompressed Linear PCM just like CD Audio. DTS-HD MA and TrueHD are lossless compression schemes aka codecs. DTS-HD (without the "MA") is a very high bitrate, yet LOSSY codec. DTS-HD Master Audio (or "MA" as most of us call it) is lossless.

So I ask this question would you rather listen to DTS-HD MA 24bit/48kHz since the disk has enough space for it or a "downres" the 24-bit, 48kHz LPCM master track to 16-bit, 48kHz LPCM?
I dont know the answer and I dont know if my ears can even tell.

LPCM offers nothing over TrueHD except it takes about about 2-3x the space. Either your player or receiver needs to support TrueHD and DTS-MA. But if the HD movie is mastered theoretically up to 192/24 (I don't think anything is done this high) you can fit a DD TrueHD and DTS-MA into the disks. Theres not enough room to have LPCM 192/24 in todays disks. We might need to wait for the quad sided Blue Ray disk on the PS5

Please correct any assumptions above.

Sat, the bottom line is that as far as formats go, and as recent tests have confirmed, the 16 bit 44.1KHz sampling rate standard CD meets or exceeds any requirements for frequency response of human ears and dynamic range possible for the source material involved. Of course the CD format is uncompressed per se and lossless compression should be equally good, as far as is known. Variations in the original recording process and later processing steps can make differences audible with any format, of course.

What tests are those John? I've read differently.

Mike, I've made the point about the complete sufficiency of the 16/44.1 CD format as far as actual audibility goes quite a few times here in the past few years. First, there was what appeared to me to be fairly obvious in that a 22.05KHz frequency limit exceeded human needs and a 98dB(6.02n + 1.76dB)maximum dynamic range exceeded the most dynamic recordings, which at most have about a 70dB range. Then, I also cited the explanation given on the S&V board by "Soundhound", a very experienced movie music engineering editor, who detailed how while using higher bit depth and sampling rates was fine to give room during the recording process, reducing this to 16/44.1 in the actual end product made no audible difference in his tests.

The recent tests confirming this that I referred to were published in a paper in the September AES Journal. The Journal isn't available online,but here's a brief description and discussion of the tests by the editor of the Audio Critic(an engineer). In brief, when DVD-A or SACD material was run through a 16/44/1 A/D/A to limit it to 16/44.1 no difference was detected in the blind testing. Any superior production values that resulted in better sound on the DVD-As or SACDs were unrelated to higher sampling and/or bit rates in the actual end product that was listened to.

Sorry John.... I mean no disrespect or to doubt you, but I am not buying that. The audio I've heard from 24 bit / 96 kHz is startling. Unless you have personally sat in on these “tests”, then I’d suggest you do so before making blanket statements. You just might be in for a hell of a surprise.

The trouble I see with saying, "you have to personally sit in on any test I doubt" is that then you can't believe anything anyone tells you. At some point you have to believe an authority of some kind.

I think there's still room to have doubts, and I see nothing wrong with wanting further verification. I'm willing to believe that perhaps CD audio is as far as we need to go with 2-channel, but for whatever reason, I find a lot more demo material in my SACD collection than in my whole CD collection. I'm willing to accept that this could merely be the extra channels at work, or a coincidental superior sound engineering for those discs, but it doesn't change the fact that from an audio quality perspective, I'm getting more out of a format that isn't CD. So, while I'm willing to go along with the idea that CDs CAN provide for the full range of human audibility, I'm still not 100% certain that there's not more to it.