PCM or bitstream...
steveinaz
Posts: 19,545
No matter how much information I read on this, I come away confused.
With my setup, which is 2-channel audio run via Toslink, should I run PCM or bitstream from my DVD players? I'm using an external DAC (Benchmark)...
Can you school me on the differences please? Is one better quality audio?
With my setup, which is 2-channel audio run via Toslink, should I run PCM or bitstream from my DVD players? I'm using an external DAC (Benchmark)...
Can you school me on the differences please? Is one better quality audio?
Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
Post edited by steveinaz on
Comments
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My bedroom setup is similar (2-channel with toslink going from HD-A3 to Theta DAC to HK 3480).
I think I have mine set to PCM just to make sure the DAC is getting stereo information. If this is incorrect, I'd love to know as well.
As I understand it, PCM is downmixed / 2 channel information. Bitstream will give you all channels of information for the selected dvd track (typicallly 5.1 DD/DTS, some you can choose a stereo version). Not sure what my stereo DAC would do if it received a 5.1 bitstream signal.Stereo Rig: Hales Revelation 3, Musical Fidelity CD-Pre 24, Forte Model 3 amp, Lexicon RT-10 SACD, MMF-5 w/speedbox, Forte Model 2 Phono Pre, Cardas Crosslink, APC H15, URC MX-950, Lovan Stand
Bedroom: Samsung HPR-4252, Toshiba HD-A2, HK 3480, Signal Cable, AQ speaker cable, Totem Dreamcatchers, SVS PB10-NSD, URC MX-850 -
Your 2 channel DAC cannot decode Dolby Digital or DTS signals. If your 2 channel DAC gets sent these types of signals, the DAC will just give you a bunch of pink noise.
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(I think*) My Benchmark DAC1 is accepting and using "bitstream" input from my BluRay (via Toslink), but I'm wondering if that's optimal for a 2-channel system?Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
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mightymouse wrote: »Your 2 channel DAC cannot decode Dolby Digital or DTS signals. If your 2 channel DAC gets sent these types of signals, the DAC will just give you a bunch of pink noise.
Really? Maybe I'm full of crapola, I need re-check my settings tonight, but I believe my BD30 was set at "bitstream." Maybe this setting is for the HDMI connection??
See why I'm confused?
Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2 -
mightymouse wrote: »Your 2 channel DAC cannot decode Dolby Digital or DTS signals. If your 2 channel DAC gets sent these types of signals, the DAC will just give you a bunch of pink noise.
This is what I assumed would happen, that's why I have my HD-A3 digital output set to PCM / Stereo instead of bitstream.
Steve, if your DAC is working with it set to bitstream, try PCM and see what sounds better.Stereo Rig: Hales Revelation 3, Musical Fidelity CD-Pre 24, Forte Model 3 amp, Lexicon RT-10 SACD, MMF-5 w/speedbox, Forte Model 2 Phono Pre, Cardas Crosslink, APC H15, URC MX-950, Lovan Stand
Bedroom: Samsung HPR-4252, Toshiba HD-A2, HK 3480, Signal Cable, AQ speaker cable, Totem Dreamcatchers, SVS PB10-NSD, URC MX-850 -
I think I might be looking at an HMDI audio setting or something--I dunno--but could swear it said "bitstream" and it works thru my Benchmark. lemme look up my manual on line, and see....hmm...Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
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Ok, manual says PCM for 2-channel audio...I'm surprised the DAC is working with bitstream..Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
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If you are using an external DAC and want zero decoding done by the player, set the player to Bitstream. If you want the player itself to do the decoding, use PCM.
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Really? Maybe I'm full of crapola, I need re-check my settings tonight, but I believe my BD30 was set at "bitstream." Maybe this setting is for the HDMI connection??
See why I'm confused?
You're not . . . my DLIII would read bitstream. It's better. You don't want some other DAC decoding before the Benchmark. -
Ahhhhh...cool, so it's like the video side where you either let the player upconvert or the display kind of thing?Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
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Ahhhhh...cool, so it's like the video side where you either let the player upconvert or the display kind of thing?
Well, kinda... Your display will always convert to it's native resolution regardless. Unless, you have a fancy scaler that will send your dispay it's exact raw resloution, like 1368x768 for example. There is usually some sort of "upconverting" being done by your display... -
Is there a difference in sound quality betwen PCM and bitstream?Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
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Steve,
In your case the BEST sound quality is going to be achieved with "bitstream" as compared to PCM. You want your fancy DAC to do the decoding, not some cheapo one in your player and decoded again with your DAC.(Like what SS stated earlier)
If you are using HDMI and have a PS3 for example, in order to get the latest and greates audio formats you'd need to set the PS3 to PCM to utilize the newer audio codecs. Hence, PCM = player decoding and sending the signal, Bitstream = player sending your DAC or AVR a raw digital signal for some other device to the decoding. -
So, I have a fancy DAC but it's from the early 90's, Theta Pro Progeny. It will accept a DD Bitstream signal and convert it down to a 2-channel mix?Stereo Rig: Hales Revelation 3, Musical Fidelity CD-Pre 24, Forte Model 3 amp, Lexicon RT-10 SACD, MMF-5 w/speedbox, Forte Model 2 Phono Pre, Cardas Crosslink, APC H15, URC MX-950, Lovan Stand
Bedroom: Samsung HPR-4252, Toshiba HD-A2, HK 3480, Signal Cable, AQ speaker cable, Totem Dreamcatchers, SVS PB10-NSD, URC MX-850 -
So, I have a fancy DAC but it's from the early 90's, Theta Pro Progeny. It will accept a DD Bitstream signal and convert it down to a 2-channel mix?
Sure, I don't see a problem with that. -
I get confused by this stuff too, I feel old like I need to get my 13 year old nephew to explain it to me
I am still not clear on the toslink, the ps3 puts out pcm because everything is internally decoded, but I don't think toslink has the bandwidth to carry all the info of the audio track from blue ray, is that right?
Is toslink only 2 channel or can that do 5.1??
There is so much awsome gear that is on the cheap right now because it has no hdmi.
Hey, I learned the real reason for hdmi is to enforce drm. With component there is no 2 way handshake to keep from pirateing. -
Steve,
In your case the BEST sound quality is going to be achieved with "bitstream" as compared to PCM. You want your fancy DAC to do the decoding, not some cheapo one in your player and decoded again with your DAC.(Like what SS stated earlier)
If you are using HDMI and have a PS3 for example, in order to get the latest and greates audio formats you'd need to set the PS3 to PCM to utilize the newer audio codecs. Hence, PCM = player decoding and sending the signal, Bitstream = player sending your DAC or AVR a raw digital signal for some other device to the decoding.
Thanks Mike, that's what I was thinking, but this DVD audio stuff/codecs is real complex with all these formats.Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2 -
Thanks Mike, that's what I was thinking, but this DVD audio stuff/codecs is real complex with all these formats.
Mike is wrong in this instance. You guys are getting confused between decoding and D/A converting. The Benchmark will only do D/A converting. It cannot decode an AC3 (Dolby Digital), DTS, or any other bitstream signal. A decoder chip is required for that, not a DAC.
The only thing the Benchmark can deal with is PCM signals. (see pages 10-11 of the manual)
Steve, most likely what is happening is the BD30 is sending PCM over optical/coax despite having Bitstream selected.
There are a couple reasons this could happen. 1st, there are several places to select Bitstream vs PCM. In each of the surround formats AND in the Digital Audio Out. If you have the Digital Audio Out is set to PCM, the player will send 2-ch PCM over the coax/optical no matter what you have set for Dolby Digital, TrueHD, DTS, etc.
Another reason this could happen is because you have the HDMI out from the BD player hooked directly to a TV. If you do this and you have HDMI audio set to ON, then the player recognizes the TV as a 2-channel device and it automatically down-converts everything to 2-channel.
See page 21 of the BD30 manual for details on how the BD30 handles all these options.
Bottom line, the Benchmark needs to see PCM. -
I get confused by this stuff too, I feel old like I need to get my 13 year old nephew to explain it to me
I am still not clear on the toslink, the ps3 puts out pcm because everything is internally decoded, but I don't think toslink has the bandwidth to carry all the info of the audio track from blue ray, is that right?
Is toslink only 2 channel or can that do 5.1??
There is so much awsome gear that is on the cheap right now because it has no hdmi.
Hey, I learned the real reason for hdmi is to enforce drm. With component there is no 2 way handshake to keep from pirateing.
TOSLINK can do 5.1 in the old formats (DD/DTS), but HDMI is needed to do multichannel PCM and that is how the PS3 sends out the TrueHD/DTSHD and lossless LPCM signals. -
Mike is wrong in this instance. You guys are getting confused between decoding and D/A converting. The Benchmark will only do D/A converting. It cannot decode an AC3 (Dolby Digital), DTS, or any other bitstream signal. A decoder chip is required for that, not a DAC.
The only thing the Benchmark can deal with is PCM signals. (see pages 10-11 of the manual)
Steve, most likely what is happening is the BD30 is sending PCM over optical/coax despite having Bitstream selected.
There are a couple reasons this could happen. 1st, there are several places to select Bitstream vs PCM. In each of the surround formats AND in the Digital Audio Out. If you have the Digital Audio Out is set to PCM, the player will send 2-ch PCM over the coax/optical no matter what you have set for Dolby Digital, TrueHD, DTS, etc.
Another reason this could happen is because you have the HDMI out from the BD player hooked directly to a TV. If you do this and you have HDMI audio set to ON, then the player recognizes the TV as a 2-channel device and it automatically down-converts everything to 2-channel.
See page 21 of the BD30 manual for details on how the BD30 handles all these options.
Bottom line, the Benchmark needs to see PCM.
Thanks Bill
I definitely need to get educated on this stuff. I'll crack that DVD menu open tonight again and go through the settings. I didn't think the Benchmark would accept bitstream, but the key word there is "think."
Maybe I'm confusing the hell out of my BD30 because the video is connected via HDMI, but the audio is connected via Toslink?
Your exactly right on the HDMI audio, I have it set ON/2-channel. This allows the flexibilty to watch DVD's with or without the audio system on. I thought that I recalled in the past with other DVD players, if I selected anything but PCM, I got no audio out of Toslink. That's what had me confused--that this player "appeared" to be outputting bitstream. Well, at least it's "Steve proof"..LOL
I feel for you multi-channel people, you damn near need a college course on this stuff to grasp it all. Holy crap.Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2 -
Here's an interesting twist, I was seeing bitstream in the menu, but the firmware update I did last night (1.8) on the BD30 corrected the menu to read "PCM" now. Cool.
Thanks for all the help fellers.Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2 -
Mike is wrong in this instance. You guys are getting confused between decoding and D/A converting. The Benchmark will only do D/A converting. It cannot decode an AC3 (Dolby Digital), DTS, or any other bitstream signal. A decoder chip is required for that, not a DAC.
The only thing the Benchmark can deal with is PCM signals. (see pages 10-11 of the manual)
Steve, most likely what is happening is the BD30 is sending PCM over optical/coax despite having Bitstream selected.
There are a couple reasons this could happen. 1st, there are several places to select Bitstream vs PCM. In each of the surround formats AND in the Digital Audio Out. If you have the Digital Audio Out is set to PCM, the player will send 2-ch PCM over the coax/optical no matter what you have set for Dolby Digital, TrueHD, DTS, etc.
Another reason this could happen is because you have the HDMI out from the BD player hooked directly to a TV. If you do this and you have HDMI audio set to ON, then the player recognizes the TV as a 2-channel device and it automatically down-converts everything to 2-channel.
See page 21 of the BD30 manual for details on how the BD30 handles all these options.
Bottom line, the Benchmark needs to see PCM.
Bill,
Very interesting.:o Don't listen to me Steve, I taught for sure I had this area down pat...
One question though... In Steve's case, would he be getting a signal converted twice in this instance, since he is sending the signal via LPCM? I'm getting confused on this also; however, I've also never used an external DAC.
Mike -
Bill,
Very interesting.:o Don't listen to me Steve, I taught for sure I had this area down pat...
One question though... In Steve's case, would he be getting a signal converted twice in this instance, since he is sending the signal via LPCM? I'm getting confused on this also; however, I've also never used an external DAC.
Mike
No, not converted twice. Once its PCM, it is decoded, but still digital. It stays in that format and the Benchmark converts it into Analog.
Now, lets say, he was sending analog out to a receiver that did its own bass management. That would be converting it twice. It would get decoded by the player, then converted to analog, then the receiver would re-covert to digital, run it through a DSP, then it would convert back again to analog. That's what you want to avoid.
All in all, there is usually no drawback to letting the player decode to PCM unless it is down-sampling for some reason, but that wouldn't be the case with Steve. Most of the time, decoding is either right or wrong, it is all in the digital domain, so there is little difference in sound between one decoder to another, as long as the programing (firmware) tells it to decode it the right way. The difference in sound comes from DSPs, DACs and analog stages. You will actually find that there are only a handful of decoder chips out there for any given format and many players end up using the same chips. -
I think people might be getting confused on why DACs or decoding is needed in the first place.
On the decoding front, Dolby or DTS are "compressed" signals to save space just like a gif is a compressed image file on a computer that makes for a smaller file than the original raw image file that comes out of a high quality digital camera. It isn't encoded to increase the quality of the audio information. And in fact, unless the compression is a "lossless" format, it will degrade the quality of the audio by losing information during the compression process.
When you uncompress (decode) the Dolby or DTS signal, it uncompresses to PCM. Now with blu-ray, you have lossless Dolby and DTS formats (TrueHD and DTS-HD MA) that decode to the original PCM signal and don't lose quality in the compression. And the third lossless format, uncompressed LPCM, was never compressed in the first place (meaning the file is large and eats up disk space) but doesn't need to be "decoded". But in order for the receiver/pre to apply all the fancy digital processing (all the different surround modes), the signal must eventually be PCM. But it doesn't matter where it's decoded, as long as the receiver/pre's digital processing path receives PCM.
DAC's are digital analog converters, IIRC. They are necessary to convert the digital information to the analog electrical signals that make it out to the amp and then the speakers. An extra conversion to analog occurs when the player transmits analog over the analog outs to the receiver/pre. But this is bypassed by the player sending the information digitally over toslink or hdmi, with hdmi being necessary for the lossless formats. -
No, not converted twice. Once its PCM, it is decoded, but still digital. It stays in that format and the Benchmark converts it into Analog.
Now, lets say, he was sending analog out to a receiver that did its own bass management. That would be converting it twice. It would get decoded by the player, then converted to analog, then the receiver would re-covert to digital, run it through a DSP, then it would convert back again to analog. That's what you want to avoid.
All in all, there is usually no drawback to letting the player decode to PCM unless it is down-sampling for some reason, but that wouldn't be the case with Steve. Most of the time, decoding is either right or wrong, it is all in the digital domain, so there is little difference in sound between one decoder to another, as long as the programing (firmware) tells it to decode it the right way. The difference in sound comes from DSPs, DACs and analog stages. You will actually find that there are only a handful of decoder chips out there for any given format and many players end up using the same chips.
Thanks for clarifying that Bill, my bad for passing the wrong information.:o I'm glad someone squared me away... -
Great information guys, thanks! I have the BD30 set to PCM/No down conversion. My Oppo DV-980H comes in tonight, so I'll get it setup as well.Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
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With SD DVD, you would always want to choose PCM in a 2-ch DAC scenario because PCM is what a 2-ch DAC processes. It can't handle a DD or DTS bitstream. In this case, you would only choose bitstream if you are sending the signal to a surround processor or receiver. Also in this case, the DD or DTS surround track will be down-mixed to 2-ch PCM if you choose PCM in the set-up menu.
As a side note, some DVDs (mainly concerts) contain an uncompressed PCM stereo track in addition to DD or DTS. This PCM track is often higher than standard redbook PCM resolution of 16 bit/44.1 kHz. I have concerts that have up to 24 bit/96 kHz resolution in the PCM track. So, in a 2-ch DAC scenario, always choose the 2-ch PCM track or stereo option if it exists on the disc's menu, as you will get the highest resolution, uncompressed track.
With BR, maybe it gets a little more confusing because PCM and bitstream could output the same data in the case where the soundtrack is PCM to begin with. I'm fuzzy on this myself, so I could be wrong. Nonetheless, your DAC needs a PCM signal, so that seems like the logical choice for your BR player too.5.1 and 2.0 ch Basement Media Room: Outlaw 975/Emotiva DC-1/Rotel RB-1582 MKII/Rotel RB-1552/Audiosource Amp 3/Polk LS90, CS400i, FX500i/Outlaw X-12, LFM-1/JVD DLA-HD250/Da-Lite 100" HCCV/Sony ES BDP/Sonos Connect. DC-1/RB-1582 MKII/Sonos Connect also feed Polk 7C in garage or Dayton IO655 on patio.
2.1 ch Basement Gym: Denon AVR-2807/Klipsch Forte I or NHT SB2/JBL SUB 550P x 2/Chromecast Audio.
2.0 ch Living Room: Rotel RX-1052/Emotiva DC-1/Klipsch RF-7 III/Sony ES BDP/LG 65" LED.
2.0 ch Semi-portable: Klipsch Powergate/NHT SB3/Chromecast Audio.
Kitchen: Sonos Play5. -
Yep, both players are set to PCM, all is good in the audio kingdom.Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Source: Rotel CD14MkII CD Player - Speakers: Elac Debut 2.0 B5.2
