5.1 AC3 downmixing to stereo

Hi,
I am currently working on a workflow to create my own AVCHD discs (Blu-Ray on a DVD-R) from my Sony SR11 without editing or transcoding in Premiere. I import the files directly into Encore after demuxing them using tsMuxer (I need to demux them first because for some reason, Encore will refuse to import my muxed stream complaining about too many audio channels). The demuxed sound files are 5.1 AC3 Dolby files. When I create a timeline in Encore and add one of my video/audio file, the generated audio in the final disc is Dolby 5.1. However, if I include more than one video/audio pair, the program goes through a short transcode stage and the audio is converted to Dolby Stereo on the generated disc.
Any idea why?
Darth

This is my second BD title that I've authored in Encore CS3 and this time around, I am having the same problem with Encore mucking with my 5.1 .ac3 file and converting it to 2 channel PCM. HOWEVER, I am not trying to join .ac3 files on one timeline. I have a dedicated timeline for each program on the disc.
I went back into the Project tab to see what the status was, and I see it shows "transcoded" so I changed the asset to "do not transcode" and burned another image. Unfortunately, Encore sabotaged my audio again, and there goes another $21 BD-R disc--the audio shows up as 2 ch PCM on the Sony BDP-S301 player, NOT the original 5.1 AC3 Dolby that was encoded from the DVD version of this program.
I don't know what is different about this project (I could have sworn my previous project containing a 90-minute concert left the AC3 audio in surround format) but I can't seem to feed it surround audio anymore and have it remain UNADULTERATED by Encore. Setting the attribute to "don't transcode" is apparently a joke--Encore ignores it and just does what it wants. I find a 1 GB .wav file in the transcoded files\ folder after each disc rendering session.
More perplexing is that on a prior BD I authored last year, I didn't have to do anything to the flags--5.1 ch ac3 remained intact and Encore seemed to know enough to leave it alone. But now it transcodes all ac3 audio to 2 ch PCM and I'm burning through an expensive and precious supply of BD-R media, trying to achieve a disc with 5.1 surround, as the original source files provided to Encore are.
I'm at wits' end. This is just one of a slew of things I hate about Encore, which reminds me a lot of editing in Dazzle's DVCII MovieStar application on a Pentium 400--glacially slow at repositioning in the timeline, garbage quality previews that don't manage even 1fps at 12 dots per inch, unstable, and always out of memory. How I long to be authoring in Scenarist BDMV!

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Can Compressor downmix from stereo (dual mono) to mono?

Seemingly simple question - when compressing DV/AIFFs to web H.264/AACs, is there a way to downmix from stereo(dual mono) to mono without boosting the level?
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(NOTE: without using the Peak Limiter filter to lower the level, which always seems to cause the job to fail)

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/R

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I do not believe that there is an SPRM in the spec for "default # of playback channels". There is an SPRM for audio format, but both streams will be AC3 in your case.
I would do two things -
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Now I know to choose Add Surround Sound in the batch window and assign each track it's respective position, but what isn't clear is the setting I choose to encode to AC3. I would assume that I choose AC3 5.1 under the audio presets, but the audio config looks odd to me, so instead of waiting for the encode to complete only to find out I was wrong, I thought I would ask beforehand.
Thanks!

The correct setting to use is Apple > Formats > Audio > Dolby Digital Professional 5.1.
The Audio Coding Mode defaults to L, C, R, Ls, Rs, which is what you should have set
in the Add Surround Sound interface.
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What I want to do is I have a number of HD/SD media that all have 5.1 Surround and I am simply wanting to merge them together into one big clip, with maybe some fine tuning of the clip length nothing fancy, but I want to retain the AC3 5.1 Surround sound content. Any ideas? I have FCE will that help me?

I am trying to figure out how to edit video content I exported from a VOB file that the audio is in AC3.
AC3 content is not editable in QT applications.
I have used tools like StreamClip to export the file into a QT MOV format, but there are no AC3 options.
MPEG Streamclip by default down-mixes 5.1 (3/2) AC3 down to stereo. (Other options include: Front Mix, Surround, L/R Ch., Center Ch., LS/RS Ch., and LFE ch. which can then be exported as stereo or mono.)
So I DEMUX the audio to AC3 and try to add that to iMovie 08 and still no luck.
As stated above, iMovie '08 does not support AC3 as a compression format. In addition, iMovie '08 cannot access third-party components so even if you have an AC3/A52 component installed, it will not work. Further, even if it did support AC3 compressed audio, iMovie '08 itself only supports stereo audio.
Looks like 08 does not support m2v format.
iMovie '08 will support M2V video content in an MOV file container if and only if all P- and B-frames have been converted to I-frames making the file equivalent to a Motion-JPEG video clip.
I have FCE will that help me?
Not Really.
What I want to do is I have a number of HD/SD media that all have 5.1 Surround and I am simply wanting to merge them together into one big clip, with maybe some fine tuning of the clip length nothing fancy, but I want to retain the AC3 5.1 Surround sound content.
In the end, all of the various possible work flows depend on how you plan to play the content. This, in turn, determines which work flow is best suited to your needs. Basically you can convert and then edit in QT editor applications or edit in MPEG Streamclip, (save,) and then convert for a final target use/device.

5.1 in stereo?

I'm just wondering ... if a 'surround' mix heard only in stereo sounds more interesting than a straight stereo mix? Does any of the surround mix translate to stereo?
Ben

Typically, yes.
When downmixing to stereo is done by a set-top box (DVD player, usually), the center channel - where best practice says you should place all your dialogue - is split between the left and right, but that's not a huge gain since dialogue is usually set to zero pan in a stereo mix anyway.
Most native stereo mixes (meaning not Pro-Logic encoded), however, do not attempt to simulate surround effects but when downmixing 5.1 to stereo, the set-top will phase-shift the left and right surrounds 90º and place them in the left and right (stereo) speakers. That typically adds up to a much richer aural experience. Especially with mixes that aggressively use surrounds.
The LFE channel - my favorite part of a 5.1 mix - is completely dropped when downmixing though.

[Solved] How to keep the channels of stereo audio "as is"?

I'm using a 5.1 surround sound system with ALSA/PulseAudio. I'm using HDMI to transmit to the receiver to power all speakers up. It works for movies without any issue especially after I passed "audio-channels=6" to mpv. But I notice that when I play a stereo audio, the sound comes from all speakers / channels. For example:
$ aplay -c 2 /dev/urandom
Playing raw data '/dev/urandom' : Unsigned 8 bit, Rate 8000 Hz, Stereo (but all six speakers are working)
Does PulseAudio remix the audio? It's a nice feature for minimal multimedia speakers. But for some audio, it sounds better by just using to 2 channels as it recorded, and my receiver has enough DSP stuff and audio effects to remix the audio and to use all my channels (i.e I don't want to double-remix the audio). It should use the channels as it recorded. Is there a way to keep the channels of stereo audio "as is"?
Thanks for any advice.
Last edited by biergaizi (2015-04-05 05:31:07)

The "enable-remixing" is the setting the OP is looking for. It will disable remixing completely if set to "no", with the drawback that, say, 5.1 audio won't be downmixed to stereo if one only has 2 channels.
Disabling remixing globally seems to have weird side effects, I couldn't get my front connectors working after disabling it.
What I did was splitting my 7.1 device into a 5.1 and a 2.0 virtual devices, leaving the global remixing setting at default. Then I disabled the remixing for the 5.1 virtual device, while letting it remix for the 2.0 one.
So now when I want to remix, I just select my 2.0 device, and if I don't, the 5.1 device (or rather, in my case I actually have a 5.1 and a stereo device connected). The example is on the wiki

XtremeMusic digital out: stereo? 2.1? passthrou

Hi all,
Every X-Fi Card has FlexiJack with a 3-in- function (Digital IO/ Line In / Microphone). This jack can be used to connect to the receiver's Coaxial In (via minijack to rca adapter).
So here is the question:
can the XtremeMusic Card be connected to the reciever only via digital coax and
- pass stereo fram mp3s/CDs/etc
- pass-through the compressed AC3/DTS signal from movies
- decode the AC3/DTS to stereo and pass it digitally to the receiver
Many thanks
drjack

You could use a 3-Ft. Gold Series Stereo Y-Cable, Phono Plugs to /8" Jack.
The /8" Jack plugs into the FlexiJack/digital output of X-Fi SB XtremeMusic.
Red RCA : Digital Out
White RCA : Digital In
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http://us.creative.com/products/prod...subcategory=55

Merge .ac3 and uncompressed

i need to merge an .ac3 audio file and a separate uncompressed picture into an uncompressed quicktime file

hello russ
that was fast. thanks. did exactly as you asked, and the results worked like a charm. nice, elegant
but there's a critical problem: it seems as if the .ac3 file was stereo encoded (mixed down) in the resultant QT output. this is exactly what premiere cs 6 does. i was wondering if the same is true of final cut x & compressor? i need a QT playback device to recognize the embedded audio as an .ac3 (dolby digital), and not LtRt or stereo track. any ideas?
here is the header info from the merged file exported through mpeg streamclip:
General
Complete name : /images/Crazy_ac3/crazy_comp_ac3/crazy_1920_1080_29.97fps_5.1_comp.mov
Format : QuickTime
Format/Info : Original Apple specifications
File size : 5.32 GiB
Duration : 1mn 0s
Overall bit rate : 760 Mbps
Encoded date : UTC 2013-01-26 00:36:31
Tagged date : UTC 2013-01-26 00:39:48
Writing library : Apple QuickTime
Video
ID : 1
Format : RLE
Format/Info : Run-length encoding
Codec ID : rle
Duration : 1mn 0s
Bit rate : 758 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 fps
Bits/(Pixel*Frame) : 12.197
Stream size : 5.31 GiB (100%)
Language : English
Encoded date : UTC 2013-01-26 00:36:31
Tagged date : UTC 2013-01-26 00:39:48
Audio
ID : 2
Format : PCM
Format settings, Endianness : Big
Format settings, Sign : Signed
Codec ID : twos
Duration : 1mn 0s
Bit rate mode : Constant
Bit rate : 1 536 Kbps
Channel(s) : 2 channels
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Stream size : 11.0 MiB (0%)
Language : English
Encoded date : UTC 2013-01-26 00:36:31
Tagged date : UTC 2013-01-26 00:39:48

AC3 import now an option?

Is ac3 import supported (stereo and 5.1)in Premiere CS4?
Cheers!

See:
FAQ:What file types does Premiere Pro support?
Cheers
Eddie
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CS3 - what container/wrappers does it accept?

I asked this on the Premiere forum, but I suppose it's more of an Encore thread so I'm re-posting on here
looking at the FAQ I can see what codecs it accepts but not what containers/wrappers it accepts those codecs in:
http://livedocs.adobe.com/en_US/EncoreDVD/3.0/help.html?content=WS5C9E1CF8-B5BC-436f-89D3- 61DDC02A2C47.html
does anyone know if any of the following will import?
1080i/1080p mpeg2 with AC3 5.1 audio in TS container (.ts)
720p mpeg2 with AC3 5.1 audio in TS container
1080i/1080p h.264/avc with AC3 5.1 audio in TS container
1080p wmv-hd VC-1 with wma 5.1 audio in WMV container
720p h.264 with AC3 5.1 audio in MKV container
1080i/1080p h.264/avc with AAC 5.1 audio in MP4 container
most Hi-def videos these days are in these formats and I'm wanting to back mine up to Blu-ray and keep the 5.1 audio with no downmixing to stereo. Can Encore handle any/most/all of these formats?
If it can't, can anyone suggest what to use to convert them to a format Encore would allow (except mpeg2 TS files which I can convert to mpeg2 PS or elementary streams)
any help/advise would be greatly appreciated

@ Matthew.
Er, no chance will I be trying
i that
out!
AC3 is already heavily compressed, so decoding to WAV and recompressing again is going to create a file that sounds bloody awful. Once the data has been tossed out in the original AC3 (Dolby Digital 5.1) creation, it is gone forever - and we are talking 6 channels at a minimum of 6,144 kbps to DD at 448 kbps. That's a lot to throw away, and it cannot be recovered again. If you started with 24 bit audio & used a licensed encoder, the loss is paradoxically not so great.
(Wonder if the DD Decoder is actually licensed, or a hack job?)

How is the iPad processing 5.1 AAC

Lately I happened to have a video file which has AC3 audio. I tried to change the container from MKV to MP4 with Subler for iTunes and my iPad but it didn't work with my iPad (syncing failed).
Previously I've always had either AAC stereo only or AC3 Surround + AAC stereo (Dolby Pro Logic II). So I figured that it may have something to do with only having AC3 in my video file.
Next thing I did was converting the audio line of the video file with Handbrake (along with low settings for the video so it doesn't take too long) to AAC. But not Dolby Pro Logic II or normal Stereo but AAC Surround (6 channels). I've never done that before but after merging the new audio with the H.264 video in Subler syncing with my iPad worked without a flaw.
But since the iPad can only play stereo through it's speakers / headphone cable (and I know it can push AC3 through the adapter but I am not using this) I am wondering what the iPad is doing with the center channel + surround channels.
Am I loosing the additional content when I am listening to it with headphones or does the iPad downmix it to stereo?
And one additional question: Did the syncing really fail because the video file had only AC3 in it?
Off-Topic: Thanks to the moderator who accuses me of doing illegal actions which is ridiculous. Someone who plucks something out of the air shouldn't be a moderator in this community.

Lately I happened to have a video file which has AC3 audio. I tried to change the container from MKV to MP4 with Subler for iTunes and my iPad but it didn't work with my iPad (syncing failed).
Previously I've always had either AAC stereo only or AC3 Surround + AAC stereo (Dolby Pro Logic II). So I figured that it may have something to do with only having AC3 in my video file.
Next thing I did was converting the audio line of the video file with Handbrake (along with low settings for the video so it doesn't take too long) to AAC. But not Dolby Pro Logic II or normal Stereo but AAC Surround (6 channels). I've never done that before but after merging the new audio with the H.264 video in Subler syncing with my iPad worked without a flaw.
But since the iPad can only play stereo through it's speakers / headphone cable (and I know it can push AC3 through the adapter but I am not using this) I am wondering what the iPad is doing with the center channel + surround channels.
Am I loosing the additional content when I am listening to it with headphones or does the iPad downmix it to stereo?
And one additional question: Did the syncing really fail because the video file had only AC3 in it?
Off-Topic: Thanks to the moderator who accuses me of doing illegal actions which is ridiculous. Someone who plucks something out of the air shouldn't be a moderator in this community.

H.264 or MPEG2 in TS conainer

Before I purchase Premiere CS3 I wondered if anyone knew if it will imort the following (or if Encore will):
1080i/1080p mpeg2 with AC3 5.1 audio in TS container (.ts)
720p mpeg2 with AC3 5.1 audio in TS container
1080i/1080p h.264/avc with AC3 5.1 audio in TS container
1080p wmv-hd VC-1 with wma 5.1 audio in WMV container
720p h.264 with AC3 5.1 audio in MKV container
1080i/1080p h.264/avc with AAC 5.1 audio in MP4 container
most Hi-def videos these days are in these formats and I'm wanting to back mine up to Blu-ray and keep the 5.1 audio with no downmixing to stereo. Can premiere handle any/most/all of these formats?
If it can't, can anyone suggest what to use to convert them to a format Premiere would allow (except mpeg2 TS files which I can convert to mpeg2 PS)
any help/advise would be greatly appreciated

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5.1 AC3 downmixing to stereo

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