Originally Posted by kenshin-dono
hmm still not clear on the real difference between bitstream and PCM. All im hearing is that suposedly PCM has a higher MBS rate or something but i dont get what the actual difference is in how they play. As i said earlier from what i read bitstream outputs the audio data directly while PCM decodes it in the player and puts it out as a different higher bit rate stream.. is this correct or not? I always thought 'pure unaltered' audio was the best bet which makes me wonder why everyone likes PCM if its mucking with the audio for TRue HD tracks and the like
see thats the thing. The brief testing i did with just kung fu panda had me switching from PCM to Bitstream with dolby Tru HD. And i'll be damned if bitstream didn't sound better. I tried the select thing and the mbs was higher with PCM but it sounded louder and crisper with bitstream.
This is what makes no sense to me.
Shouldn't the PCM sound better? It has a higher bit rate. One thing i noticed was when i switched to bitstream my reciever flashed with Dnorm +4 or something briefly. Im not sure what that means, but it didn't do that when its on PCM
If PCm supports DD and DTS and the like, whey doesn't it just show that thats whats playing instead of just having PCM on the reciever display? Thats what seems to be confusing the hell outa me. In theory from what im reading PCM has a higher bit rate so it should sound better, but the brief testing makes bitstream sound better. Bitstream supposedly streams stuff unchanged direct to the reciever so i would THINK that would be preferable over PCM which seems to screw with the audio before sending it out. I guess im not seeing what makes PCM so much better other than a higher bitrate. If its not playing the codecs right isn't that bad?
see thats the thing, it DOESNT output to 5.1 correctly. At least not for games when i just let it do auto detect for the audio and it grabs everything up to 7.1. If i play a movie it will set it to 5.1, but with games its always showing 7.1 on the reciever and im not sure if im losing audio I guess it would be best to just go in and manually disable the 7.1 options then?
Also you mention that the PS3 fat doesn't do bitstream for HD codecs.. but it doesn't doesn't it? The latest patch lets you select bitstream for the HDMI audio
I want to clarify something btw. All this bitstream/PCm thing ONLY applies to BD movies right?
It seems like for games it will always do PCM no matter what i select. If thats the case then why do games just list DTS and dolby digitial options? Am i not getting those on pcm? I think i remember uncharted had an actual option in game to switch it to DD which would change my recievers display to DD instead of PCM. I could have sworn this actually sounded better too. Whats going on there? This is probably one of my biggest concerns. Why would a game let you switch to dolby digital option if PCM is the default for all games and should sound better?
ungh this is giving me a headache.
oh ya, anyone know the answer to number 2
2) How do i find out if my receiver does multi channel PCM? Im pretty sure i read somewhere where pcm will have problems if your reciever doesn't do MCPCM. All it says on my reciever when i use linear PCM is "PCM" If i put it on bitstream it shows DD or something else. Shouldn't it say MCPCM? Maybe ballen knows since he has the next step up from my reciever? If it didn't do MCPCM would i only be gettin stereo or what?
To make it simple, the difference between bitstream and PCM, is where the audio is getting decoded. If you choose PCM, audio gets decoded from DD5.1 or DTS 5.1 or DTS-HD or whatever, to PCM and then gets sent over the audio portion of HDMI to your receiver where it's converted from digital to analog and played over your speakers. If you choose bitstream, the audio track in DD5.1, DTS 5.1, DTS-HD or whatever, gets sent directly to your receiver over the audio portion of HDMI. There it gets decoded to PCM, converted from digital to analog and played over your speakers.
So really, the choice is simply a matter of where you want the audio decoded. In some cases your receiver may not support one or another audio format and the PS3 does. So, you would choose PCM so that the PS3 would decode the audio and send it to the receiver.
I should point out that it's quite difficult to do an objective comparison between the two, if there is ANY difference in volume between the 2 cases, as listeners invariably pick the louder one as being better sounding. Ideally, whether you chose PCM or bitstream, it should sound identical.
To your question of why the receiver is just displaying PCM instead of telling you that it's DD5.1 or DTS5.1, the receiver cannot possibly know the origin of the soundtrack that was decoded by the PS3. All the receiver can know is that it is receiving multi-channel PCM. The PS3 does know and there is an overlay menu somewhere that will tell you the format of the audio track that is currently being decoded and sent as PCM to the receiver. If you want your receiver to display DD5.1 or whatever, then you must configure the PS3 to send bitstream. Then the receiver will know what is the format of the original audio track, since in that case, the PS3 sends the audio track precisely as it is read from disk with no decoding at all.
Bitstream vs PCM applies to Bluray and SD DVDs. I don't remember offhand if it applies to games also. I would think that it does.
As to whether your receiver does multi-channel PCM or just 2 channel, I would say that you ought to be able to hear the difference. Set the PS3 to PCM and play a movie, selecting DD5.1 or DTS5.1 or something multi-channel and listen, if you don't hear anything different from the rear speakers, then assuming you don't have any post-processing (dolby prologic, etc) enabled in the receiver, your receiver does not support multi-channel PCM and the PS3 is down-mixing multi-channel to 2 channel PCM and sending that to your receiver. When the PS3 and your receiver do their HDMI handshake thing, your receiver reports to the PS3 what audio formats it supports. It's very trivial technically, to support multi-channel PCM, but I wouldn't be surprised if some receivers don't support it in which case, the PS3 is forced to downmix to 2 channel stereo PCM, if you've config'd the PS3 to do the decoding by choosing PCM. If you choose bitstream, then the PS3 will send the audio track format or your choice, but it shouldn't allow you to select a format that your receiver does not support.