Hi-Rez Audio?

[mraub1]

I haven't seen any recent threads on what plans (if any) Vudu has to included any available high resolution audio tracks with HD downloads. Though this would likely make instant viewing impossible for most users, I'm more interested in availability than instant availability. Choosing movies in advance having them download to the drive is not a real drawback for me.

Any comments?

MIKE

[NA9D]

AFAIK, the Broadcom chip that is at the heart of the Vudu does not support anything above DD5.1.

I think it's a hardware problem more than anything.

[aaronwt]

They would need a box with HDMI 1.3 to allow bitstreaming of the DD+ audio.
If they do offer one in the future I will definitely buy it.

[HeadHodge]

Originally Posted by aaronwt

They would need a box with HDMI 1.3 to allow bitstreaming of the DD+ audio.
If they do offer one in the future I will definitely buy it.

Do you know anything good or bad about DTS and PCM??

I see DTS less and less as an option on DVD's but now I see "Hi-res???" PCM more and more.

I know my PhazGorzmic Directv box and my Bose supports PCM, but I don't think VUDU does.

Oh, and I think PS3 has a PCM output option too.

[NA9D]

Originally Posted by HeadHodge

Do you know anything good or bad about DTS and PCM??

I see DTS less and less as an option on DVD's but now I see "Hi-res???" PCM more and more.

I know my PhazGorzmic Directv box and my Bose supports PCM, but I don't think VUDU does.

Oh, and I think PS3 has a PCM output option too.

PCM is not necessarily high-res. Traditionally PCM (Pulse Code Modulation) has been used for stereo, non DD, content. So the Vudu does output PCM for all stereo content. As PCM is simply a digital modulation format and it says nothing about the actual content that's been put onto the stream, I suppose the had to come out with a new moniker called "Hi-Res PCM" to distinguish it from what everyone has come to understand PCM to mean which is simply 2 channel stereo over an optical or coax channel.

[HeadHodge]

Originally Posted by NA9D

As PCM is simply a digital modulation format and it says nothing about the actual content that's been put onto the stream.

So if I understand what your saying it's sorta the crux of my real question.

If PCM is just a transfer medium that VUDU supports can it (in theory) support a DD+ type format. I realize it wouldn't be DD+, but I'm thinking about some quality equivalent that PCM could support.

I wish I still had a PS3 to give you an example. But I sold that too!

[aaronwt]

Multichannel PCM will use too much bandwidth. They need to use a lossy compression format to keep the bitrate down on multichannel audio.

[NA9D]

PCM is simply a modulation format to a data stream. Consider it like FM or AM on the radio except it's a digital modulation format. Simply broken down, it's taken like this. The input analog wave form is "clocked" or "pulsed" every so often. This is known as the sampling frequency. The amplitude of the analog wave form is then assigned a particular bit value based on the magnitude. High amplitudes get a higher value. Additionally, the more bits you can assign to the various amplitude values the more accurate your data stream (ie: like 8 bit, 16 bit or 32 bit audio).

The easiest way to really think about this is to imagine a pure sine wave. Take "samples" of this sine wave every little bit and then assign numerical values to each little sample. As you can see, the more often you sample, the more information you know about the original waveform when you want to reconstruct it. Additionally, the more samples you take in the vertical axis for the amplitude, the more accurate the resolution is and the more accurate your data for reconstructing the original waveform. Obviously, unless you have a single tone, audio is much more complex than a simple sine wave, but the principal is still the same.

Now, the Nyquist sampling theorem, basically establishes that at a sampling frequency of 2x the maximum frequency in the wave form and you can accurate reproduce it. Since 20 kHz is pretty much the highest anyone can hear, with a 40 kHz sample frequency you can pretty much get pretty close to the original wave form. But there's a phenomenon called "aliasing" that occurs and so, typically, audio is "oversampled" to help eliminate that. I won't go into what causes aliasing as it's more complicated to explain but it's simply a "real world" phenomena.

This is "pulse code" modulation in it's simplest form. The input wave form is "pulsed" and a code is assigned to the amplitude of the wave form at that point. That code is then converted to binary and sent as pulses over the digital link and reconstructed at the other end.

I'm not familiar with the higher order audio formats. It's highly likely that Dolby Digital is still a PCM format but samples the waveform differently or processes it somehow. Same thing with Hi-Res PCM. It's still the same thing, but probably a higher data rate which could mean a higher sampling frequency in the horizontal axis or a larger scale of bits to choose from in the vertical axis or both.

And given that a lot of audio is also compressed to save bandwidth, the Hi-Res formats are not AFIAK.

Does this help?

[aaronwt]

DD+, Dolby TrueHD, DTS-HD, DTS-MA are all compressed to save bandwidth. Two are lossy compression algorithms and two are lossless.

While isn't PCM uncompressed audio? So it takes up more space.

[NA9D]

Originally Posted by aaronwt

DD+, Dolby TrueHD, DTS-HD, DTS-MA are all compressed to save bandwidth. Two are lossy compression algorithms and two are lossless.

While isn't PCM uncompressed audio? So it takes up more space.

I don't think PCM is anything about the compression. PCM is simply how the analog wave form is turned into the digital bit stream. Once in the digital domain, you can then compare values from the adjacent samples and eliminate certain samples if the values didn't change. That's basically how compression both in audio and video work.