Audio Format Question: Bitstream vs. LPCM

[lsiberian]

I know, it doesn't. But from a purely subjective point of view, the bitstream definitely sounded better.

The only thing I can think of from my newbie frame of mind is, the Denon's decoder is superior than the PS3's. Even though the PS3 is using a higher quality format, the Denon can still out perform it using a lesser quality format. If that makes any sense : ) Like I said, I'm still learning this stuff. I almost wish they offered "101" level classes at the Audio/Video dealers. There is so much stuff to learn, it's staggering.

Why would it sound better?

I'm not an electrical engineer, but as a software engineer I can say that it really doesn't matter where the information translation occurs. This isn't upscaling. It's simply decompressing(which uses a standardized algorithm).

Personally I don't see the need for compression anymore anyway, but studios have to justify the existence of Dolby and DTS. That's fine with me since we may need them in the future for some other reason.

 

[robbit]

Why would it sound better?

I'm not an electrical engineer, but as a software engineer I can say that it really doesn't matter where the information translation occurs. This isn't upscaling. It's simply decompressing(which uses a standardized algorithm).

Personally I don't see the need for compression anymore anyway, but studios have to justify the existence of Dolby and DTS. That's fine with me since we may need them in the future for some other reason.

Again, I don't why it would sound better, which is why I came here. Perhaps the reason is related to previous comments - LPCM is not further "boosted" by the AVR and therefore sounds weaker. I know when I set the PS3 to LPCM, I usually have to turn the volume up louder (by several decibels) in order to maintain my normal listening level. And from a qualitative point of view, the two formats sound pretty equal, with the exception that dialogue over LPCM seems overly sharp, to the point where some of it seems to distort (crackle type effect during loud or erratic speech). This effect is not consistent and varies from movie to movie (sometimes loud speech does it, sometimes it doesn't).

 

[MDS]

My Yamaha HTR 6060 will NOT boost the LFE signal by the required 10 db in LPCM mode. So, I would get weak bass in LPCM mode. So, I have no choice but to bistream the audio from my PS3 so that it sounds correct.

The +10 dB LFE boost occurs on playback for DD. When you let the receiver do the decoding (because you sent it the DD bitstream) it will perform the boost. When you use PCM out of the PS3, the PS3 did the decoding but it is not going to amplify anything - it is going to send the PCM to the receiver.

Long story short...the receiver sees PCM and has no idea that it was originally DD and should have the LFE channel boosted.

 

[jostenmeat]

Decoding is a misnomer that we all use, all the time, for the process of unpacking the codec. It's simply unzipping. There is no decoding. OTOH, some believe that digital clocking (jitter mgmt) is superior with bitstreaming. Well, then this has also been argued even at AH, what the threshold of jitter needs to be for us to even discern it.

Briefly skimming the thread, there seemed to be reason for Patrick to suspect you were outputting 2.0 PCM via optical? I have heard that the PS3 particularly does not sound good with 2.0 PCM via optical, from one person I trust. I'm not saying it's true, but he's a pretty hardcore AV fan. (He said HDMI sounded great.)

This might be fun to discuss and all, but I don't see this issue to be of much concern at all. If you can bitstream, why not, and if you can't, big deal.

 

[robbit]

Briefly skimming the thread, there seemed to be reason for Patrick to suspect you were outputting 2.0 PCM via optical? I have heard that the PS3 particularly does not sound good with 2.0 PCM via optical, from one person I trust. I'm not saying it's true, but he's a pretty hardcore AV fan.

This might be fun to discuss and all, but I don't see this issue to be of much concern at all. If you can bitstream, why not, and if you can't, big deal.

He originally thought my Denon AVR 3806 was incapable of receiving audio signals via HDMI. After discussing, he realized the AVR was capable so the whole 2.0 PCM issue is, well, a non-issue : )

 

[juiceblrc]

John,

I should have been more clear. I choose to bitsteam from the PS3 in DD or DTS rather than use LPCM from the PS3 to get DD true HD and DTS master HD. I do this as it is the only way for me to get the LFE 10db boost.

MDS,

Newer receivers do have an option to boost the LFE 10 db when receiving LPCM. It is a manual adjustment that must be set by the user. My AVR does not have this option.

I tried to argue with Yamaha many times that my AVR should be replaced as defective or be recalled since it is still under warranty. Yamaha said that the LFE +10 "FEATURE" was not available on my AVR but is on newer Yamaha Avr's. I tried to tell them this feature should be a requirement.

I still think Yamaha is wrong.

 

[MDS]

Decoding is a misnomer that we all use, all the time, for the process of unpacking the codec. It's simply unzipping. There is no decoding.

Well now, let's get into some interesting semantic hair splits.

Zipping is in effect, encoding. There are several variations on the theme but in general you are encoding by replacing long sequences of bits with shorter sequences to reduce file size. To unzip, you need to reverse that process to get back to the original.

So eg., if you were to use the ancient run length encoding compression scheme to compress the string of text 'AABBBCCCC' you'd encode that as '
A2B3C4' so you'd have 6 bytes instead of 9 bytes.To get back to the original, you need to read the encoded stream and replace 'A2' with 'AA', etc.

This might be fun to discuss and all, but I don't see this issue to be of much concern at all. If you can bitstream, why not, and if you can't, big deal.

Agreed. But I do think in many cases it's beneficial to bitstream to the receiver when possible because the receiver is the brains/router of the system and when it can detect the original format it can often apply other processes to it - for example 'late night mode' (dynamic compression) when it can detect that the stream is Dolby Digital.

 

[jostenmeat]

Well now, let's get into some interesting semantic hair splits.

Zipping is in effect, encoding. There are several variations on the theme but in general you are encoding by replacing long sequences of bits with shorter sequences to reduce file size. To unzip, you need to reverse that process to get back to the original.

So eg., if you were to use the ancient run length encoding compression scheme to compress the string of text 'AABBBCCCC' you'd encode that as '
A2B3C4' so you'd have 6 bytes instead of 9 bytes.To get back to the original, you need to read the encoded stream and replace 'A2' with 'AA', etc.

I guess I could count on you for something like that. After all, you've taught us that PCM is a bitstream too.

Agreed. But I do think in many cases it's beneficial to bitstream to the receiver when possible because the receiver is the brains/router of the system and when it can detect the original format it can often apply other processes to it - for example 'late night mode' (dynamic compression) when it can detect that the stream is Dolby Digital.

This is a good point. OTOH, because I have to manually defeat autoflagged DRC on TrueHD bitstreams with my Onkyo 805, I might* prefer the convenience that "pre-unzipped" PCM could offer. But, my Panasonic BD30 only bitstreams, so it's all a moot point.