Audio Format Question: Bitstream vs. LPCM

[robbit]

I'm fairly new to this hobby, even though I've had my entertainment system for a little while now. Recently, I've been playing around with audio formats in an effort to find the "best" setting. Also, I swear I hear anomalies with certain settings. To be specific, it sounds as if certain parts of the speech track distort, or crackle.

My latest experiment involved switching between "Bitstream" and "Linear PCM". I was under the impression that LPCM was a higher quality signal so I set all my players to output in this format (Denon DVD player, PS3). This is when I noticed the speech distortion.

One night, I switched to "Bitstream", however, the the sound was "bigger". It was pretty wierd. We were watching Twister and the sound effects just seemed much more vibrant and powerful. Also, the whole speech distortion issue seemed to be gone.

Any comments? Is it better to send bitstream? Is LPCM superior? Do I just have a defective center channel? My equipment is as follows:

2 Definitive Tech's Super Tower (Bi-Polar, 7500 I think)
1 Definitive Tech's C/L/R 2500
2 Definitive Tech's Bi-polar surround speakers.
Denon AVR 3806 A/V Receiver
Denon DVD player (don't recall model)
PS3

 

[TLS Guy]

I'm fairly new to this hobby, even though I've had my entertainment system for a little while now. Recently, I've been playing around with audio formats in an effort to find the "best" setting. Also, I swear I hear anomalies with certain settings. To be specific, it sounds as if certain parts of the speech track distort, or crackle.

My latest experiment involved switching between "Bitstream" and "Linear PCM". I was under the impression that LPCM was a higher quality signal so I set all my players to output in this format (Denon DVD player, PS3). This is when I noticed the speech distortion.

One night, I switched to "Bitstream", however, the the sound was "bigger". It was pretty wierd. We were watching Twister and the sound effects just seemed much more vibrant and powerful. Also, the whole speech distortion issue seemed to be gone.



Any comments? Is it better to send bitstream? Is LPCM superior? Do I just have a defective center channel? My equipment is as follows:

2 Definitive Tech's Super Tower (Bi-Polar, 7500 I think)
1 Definitive Tech's C/L/R 2500
2 Definitive Tech's Bi-polar surround speakers.
Denon AVR 3806 A/V Receiver
Denon DVD player (don't recall model)
PS3

To decode multichannel audio your receiver needs bit stream. If you want to play the loss less CD quality stereo sound track on some DVDs, then you need LPCM.

 

[robbit]

"To decode multichannel audio your receiver needs bit stream. If you want to play the loss less CD quality stereo sound track on some DVDs, then you need LPCM."

Ok, so when playing audio from either Blu-Ray or DVD, it's best to use bitstream? Another question, for curiosity's sake: Why is it when I set my PS3 to bitstream, it displays a warning that states certain BD audio may not be played?

 

[AcuDefTechGuy]

I've tried just about every audio format, and I personally prefer to bitstream everything to my receiver.

Theoretically it shouldn't make a lot of difference.

But subjectively, I think that bitstream gives me "better" surround sound and better bass.

 

[Patrick_Wolf]

PS3 cannot bitstream the HD formats of BD. But it can bitstream standard formats that are found on DVD. The new PS3 slim may be able to bitstream the HD formats. Not sure.

Your receiver can't decode the HD formats, nor does it have an HDMI repeater (can't process audio via HDMI). How is your DVD player and PS3 connected to your receiver?

 

[TLS Guy]

"To decode multichannel audio your receiver needs bit stream. If you want to play the loss less CD quality stereo sound track on some DVDs, then you need LPCM."

Ok, so when playing audio from either Blu-Ray or DVD, it's best to use bitstream? Another question, for curiosity's sake: Why is it when I set my PS3 to bitstream, it displays a warning that states certain BD audio may not be played?

You can only send HD loos less audio via HDMI. The receiver has to have the right decoder and be HDMI 1.3 compliant. There are only two ways to get HD loss less audio. 1). The player does the conversion, and you connect with the multichannel analog inputs. The receiver does the conversion receiving bit stream from an HDMI 1.3 compliant device, which the receiver must also be and have the correct DAC.

 

[Patrick_Wolf]

I've tried just about every audio format, and I personally prefer to bitstream everything to my receiver.

Theoretically it shouldn't make a lot of difference.

But subjectively, I think that bitstream gives me "better" surround sound and better bass.

Some BD's offer PCM and an HD format, and sometimes the HD format is 24-bit vs 16-bi for PCM. Dunno if that's significant. But, it would lead one to believe that in this instance the HD codec would be superior. Maybe that doesn't directly apply to bitstream vs LPCM though.

 

[robbit]

PS3 cannot bitstream the HD formats of BD. But it can bitstream standard formats that are found on DVD. The new PS3 slim may be able to bitstream the HD formats. Not sure.

Your receiver can't decode the HD formats, nor does it have an HDMI repeater (can't process audio via HDMI). How is your DVD player and PS3 connected to your receiver?

Ah, I see. You're correct. The 3806 cannot decode the new HD versions of audio (very unfortunately!) My DVD and PS3 are connected via HDMI.

 

[MDS]

My latest experiment involved switching between "Bitstream" and "Linear PCM". I was under the impression that LPCM was a higher quality signal so I set all my players to output in this format (Denon DVD player, PS3).

Both the bitstream setting and LPCM settings are 'bit streams' (a linear sequence of bits). The distinction between the two settings is simply where you want the audio to be decoded.

If you set it to bitstream, the player will output the bits as they are read off the disc unaltered and the receiver will have to have a decoder for the format being played. The decoder in the receiver will turn that bitstream into PCM which will then be converted to analog, amplified, and output to the speaker terminals.

If you set the player to output PCM, the player itself will decode the audio into PCM and send it to the receiver and the receiver will once again convert it to analog, amplify it, and output it to the speaker terminals.

 

[Patrick_Wolf]

Ah, I see. You're correct. The 3806 cannot decode the new HD versions of audio (very unfortunately!) My DVD and PS3 are connected via HDMI.

How about for audio? Connected via optical for the PS3 I assume. Optical or multichannel analog for the DVD player?

My rough estimate would be that when set to PCM your receiver is getting a 2.0 signal and then employing some faux multichannel setting.

 

[robbit]

How about for audio? Connected via optical for the PS3 I assume. Optical or multichannel analog for the DVD player?

My rough estimate would be that when set to PCM your receiver is getting a 2.0 signal and then employing some faux multichannel setting.

No, both devices are connected solely with HDMI (both video and audio). The Denon AVR 3806 has 2 HDMI inputs and 1 HDMI output in the back panel. It was released right around the time HDMI was being released.

 

[Patrick_Wolf]

No, both devices are connected solely with HDMI (both video and audio). The Denon AVR 3806 has 2 HDMI inputs and 1 HDMI output in the back panel. It was released right around the time HDMI was being released.

Denon's site doesn't list the 3806 has a repeater, nor a switcher, but it clearly is if you don't have to keep switching the HDMI output cable between the player & PS3. The manual says it supports LPCM over HDMI so I'll run with that.

Do you have Twister on BD or DVD? What other movies have you heard differences?

 

[robbit]

Denon's site doesn't list the 3806 has a repeater, nor a switcher, but it clearly is if you don't have to keep switching the HDMI output cable between the player & PS3. The manual says it supports LPCM over HDMI so I'll run with that.

Do you have Twister on BD or DVD? What other movies have you heard differences?

I have it on BD. I'll be checking other movies too in the near future.

 

[Patrick_Wolf]

I have it on BD. I'll be checking other movies too in the near future.

Well then that doesn't make any sense in this case. If you set BD audio set to bitstream you're only going to get lossy Dolby 5.1 from Twister. If you select LPCM, you'll get Dolby TrueHD 5.1 which is supposed to be better.

Make sure your receiver's setup is correct when feeding it LPCM. Also be sure you know what format you're listening to for Twister: Dolby or Dolby TrueHD.

 

[MatthewB.]

I did a side by side comparison using my PS3 (LPCM) and my Sony BDP-350 (bitstream) to both my Onkyo 805 and my Denon 3808ci and what I found is that bitstreaming the lossless audio sounded slightly better (more depth and clarity, but not by a huge margin) over LPCM. For me it just seemed that the recievers (as preamps) did a better job of decoding the lossless audio over having the player do it.

Gear used

Main system
Onkyo 805
Harmon Kardon PA2200 amp -bridged (center)
B&K ST1400 amp (side surround amp)
Adcom GFA-535 amp (rear channel amp)
Sony BDP-350 (bluray player)
Sony PS3
Deftech BP7001sc (mains)
Deftech LCR2002 (center)
Deftech StudioMonitor 450s (side surround)
DefTech Mythos Gems (rears)
SVS NSD 12/2 sub

bedroom system
Denon 3808ci
Kenwood KM-X1 (six channel amp)
Sony BDP-350
Sony PS3
Acoustic Research Phantom 8.1's (Mains, side surrounds)
Acoustic Research Phantom 6.2 (center)
Acoustic Research Phantom 6.1's (rears)
SVS ISD 12/2 drivers in modified DCM sub.

 

[Patrick_Wolf]

Unless you can point out specifics, the difference is most likely in your head. "Slightly" and "nothing" are very close friends. I've also read some receivers will give a slight boost in volume when you bitstream, be careful of that.

 

[allargon]

Unless you can point out specifics, the difference is most likely in your head. "Slightly" and "nothing" are very close friends. I've also read some receivers will give a slight boost in volume when you bitstream, be careful of that.

Bingo.

Moreover, a lot of receivers won't apply additional processing (e.g. boost the LFE by +10dB) to LPCM input.

 

[juiceblrc]

Allargon,

Exactly.

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.

Also (in midrange & treble) bistream is louder than LPCM mode. I tested it with my SPL meter. To some people louder is better. When I adjusted the SPL levels equal LPCM & bitsream sounded the same to me.

 

[john72953]

Allargon,

Exactly.

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.

Also (in midrange & treble) bistream is louder than LPCM mode. I tested it with my SPL meter. To some people louder is better. When I adjusted the SPL levels equal LPCM & bitsream sounded the same to me.

I thought the PS3 couldn't bitstream? The new PS3 Slim apparently does.

John

 

[robbit]

Well then that doesn't make any sense in this case. If you set BD audio set to bitstream you're only going to get lossy Dolby 5.1 from Twister. If you select LPCM, you'll get Dolby TrueHD 5.1 which is supposed to be better.

Make sure your receiver's setup is correct when feeding it LPCM. Also be sure you know what format you're listening to for Twister: Dolby or Dolby TrueHD.

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.