How to create 7.1-channel LPCM?

[Asterra]

So I've caught some hints that if I author a BDMV with MultiAVCHD, said software can accept a 7.1-channel LPCM as the audio track. I figure this is worth testing. But first, I need to know a couple of things, and hopefully you experts can help out.

1) Let's assume I have eight .WAV files of identical duration and frequency. What software would be capable of taking those eight WAVs and spitting out a 7.1-channel LPCM (which would then hopefully be something MultiAVCHD will like)?

2) What would be the correct order of the voices? I know there are several variants among the 5.1-channel options. It has to be similarly unclear for 7.1 channels. Example: 1) Front left, 2) front right, 3) center, 4) LFE, 5) middle-left, 6) middle-right, 7) rear-left, 8) rear-right. It would be a catastrophe to guess wrong, and highly inconvenient to test. I'm guessing the truth is out there somewhere.

Thanks!

[Asterra]

[Relevant note: Creating a 7.1-channel LPCM and extracting audio from a video-less AVI are separate issues, whose individual solutions, should they ultimately be forthcoming, would be of use to future persons seeking answers on either topic. Not trying to cause trouble, but they really are distinct, with the only tie being in how they relate to my particular progression of steps taken. ;p With that being said, I will gladly share with everyone whatever workflow ultimately ends up successfully producing a 7.1-channel Bluray, since it is quite evidently a process involving no small amount of rigmarole.]

I found a handy guide on creating a 7.1-channel WAV here:

http://www.microsoft.com/windows/win...ng71audio.aspx

MediaInfo confirms that there is an 8-channel PCM in the file. Unfortunately, the process contains the audio in an AVI. Also unfortunately, I don't know of any means by which I might successfully extract/convert the audio intact. VirtualDub complains about there being no video channel. That's reasonable.

I'm so close! Once I have the WAV, I should be able to use MultiAVCHD to create a 7.1-channel Bluray. (Once, that is, I have found a tutorial that actually explains how you author a disc with that thing.)

[Asterra]

For what it's worth, I discovered that Audacity can export as 8-channel PCM (wav) if you fiddle with it properly.

Unfortunately, my only real hope in authoring with a 7.1-channel audio file (MultiAVCHD) is seriously lacking tutorials - at least, anything approaching usable for BDMV authoring - and its forum link seems to be a dead-end. I have my video, I have my audio, and I have no way of turning it into a BDMV. ;p

[guns1inger]

Why not try something like TSMuxer to bring the audio and video together into a M2TS container, then use MultiAVCHD to process/convert.

[Bonie81]

8 channel (7.1 ) WAV PCM sample : Here

[poisondeathray]

IMO, 7.1 LPCM is a huge waste of bandwidth, but I guess there are no blu-ray compatible free options for 7.1 . DTS-MA license is ~$1500

You can make 7.1 WAV with avisynth soundout, or eac3to. TSMuxer will accept and you can use it to author blu-ray disk without menus. But "PCM" wave generated by Eac3to needs to be run through Pcm2Tsmu in order for TSMuxer to accept . Technically, blu-ray is supposed to use LPCM, but the other uncompressed audio options may or may not work. Before burning a BD (and making a coaster), I would mount an ISO and test with BD player software.

[El Heggunte]

Another option: you could "distribute" (downmix) the side channels between the front speakers and the rear ones, and then compress the resulting 6-channel .WAV to 5.1 AC3 (with Aften) or to 5.1 DTS with Surcode (not freeware, but not incredibly expensive either).

[Bonie81]

@ poisondeathray
- agreed

@ El Heggunte

- agreed.
For Home Theater System, 5.1 channels lays best, economical, space saver, and easy to maintain lay-out with almost same listening experience as compared to 7.1 in a living (small) room as compared to Cinema Hall.

For AC-3, it offers high fidelity, Aften follows ATSC specs and the best FREE option, of course SurCode is professional and commercial encoder.
For DTS the only option is SurCode as there is no FREE DTS encoder, but only matter with DTS files is DTS track is very bulky (big sized).

[El Heggunte]

For DTS the only option is SurCode as there is no FREE DTS encoder, but only matter with DTS files is DTS track is very bulky (big sized).

Just for the record, the DTS-HD Master Audio Suite (the $1500 product PDR mentioned) can encode to "vanilla" DTS as well, and it's *not* restricted to the DVD-Video compliant bitrates --- in fact, one may find that 960 or 1152 kbps will sound "good enough" for a 5.1 audio track.

[poisondeathray]

You might be able to make a case for 7.1 LPCM if you have a professionally recorded 8 track recording with studio setup. An audio oriented blu-ray like a concert or something. But if this is homebrew camcorder audio, I don't see the point. And if you can afford the audio gear setup to do proper recording in the first place, $1500 is chump change for the DTS-HD MA suite.

For most cases, I think bumping the video bitrate is more important than uncompressed audio

[Bonie81]

@ poisondeathray
Even producing very high quality 5.1 requires studio setup to simulate surround effect. Home brewed 5.1 does not have same effects.

@ @ El Heggunte

"...DTS-HD Master Audio Suite (the $1500 product PDR mentioned)..."

paying very high price U$1500 and compromising video bitrate to accommodate DTS, does not make any sense to me.
i would rather be very...very happy with AFTEN, for Home-Brewing 5.1. In case of commercial production I may opt for SurCode.

At this moment of posting reply, I am not pretty sure How Hardware DVD/BD players handle AAC. My expensive 7.1 system fails to recognize AAC, that is the main reason I remained aloof from AAC, I feel little in-justice for AAC. But, for those who have 7.1 PC set-up can opt for AAC too!

[Asterra]

You can make 7.1 WAV with avisynth soundout, or eac3to. TSMuxer will accept and you can use it to author blu-ray disk without menus. But "PCM" wave generated by Eac3to needs to be run through Pcm2Tsmu in order for TSMuxer to accept . Technically, blu-ray is supposed to use LPCM, but the other uncompressed audio options may or may not work. Before burning a BD (and making a coaster), I would mount an ISO and test with BD player software.

It turns out that the workflow I adopted seems to be the most hassle free:

1) Video from MeGUI/x264.
2) Audio from Audacity.
3) TsMuxer, Bluray-creating option. Nothing to check/uncheck.

I can confirm that the following channel order is accurate for Bluray playback: F-Left, F-Right, Center, LFE, M-Left, M-Right, R-Left, R-Right. The Playstation 3 elected to play the rear-surround channels through the middle-surround speakers (along with the middle-surround channels), leaving the rear-surround speakers silent, and there were no adjustments which could be made to force it to handle the audio correctly. Literally moving the PS3's HDMI cable to a standalone Sony Bluray player resulted in the 7.1 surround playing correctly.

IMO, 7.1 LPCM is a huge waste of bandwidth

As you say, the lossless compression algorithms are not exactly convenient to acquire. (Plus I find the whole arbitrary systems of amplitude control in the TrueHD/DTS-MA codecs to be highly dubious.)

For Home Theater System, 5.1 channels lays best, economical, space saver, and easy to maintain lay-out with almost same listening experience as compared to 7.1 in a living (small) room as compared to Cinema Hall.

YMMV, of course. As it happens, I gave both routes a spin: I burned both my 7.1 mix and a 5.1 mix I had prepared as a just-in-case measure (against the distressingly strong likelihood that I would not achieve 7.1). The 5.1 was constructed by method of balancing the missing mid-surrounds between the other speakers - mirroring suggestions in this thread, I see. In the end, I could definitely tell that 7.1 was giving a more discrete and appealing effect.

Really, this contention puts me in mind of the debate over the merits of HD resolutions. Why double the bandwidth for 1080p when it looks scarcely better than 720p? How about because I can, and it's better? Perhaps it would help to recall that I can only give so much bandwidth to video and the rest (some 14Mbps) is open to my humble 6Mbps audio.

You might be able to make a case for 7.1 LPCM if you have a professionally recorded 8 track recording with studio setup. An audio oriented blu-ray like a concert or something. But if this is homebrew camcorder audio, I don't see the point.

Two things: 1) The Zoom H2. Records 4-channel 24-bit, no moving parts. Completely clean. And I was able to wrangle extremely low frequencies out of it. It didn't cost thousands of dollars but anything better would be mostly just showing off. 2) How long do you suppose this video is? ;p Cap the video bandwidth (40 Mbps). Use two layers if it's much longer than an hour. Then the only argument against using whatever audio you want is if you have a boatload of audio tracks to squeeze in. Which I don't.

[Bonie81]

@ Asterra

just curious,
What is the distance between Right-Side-Surround and Right-Rear-Surround speakers?