Quantcast DVD2AVI: Should I use Dolby Surround Downmix? - digitalFAQ.com Forums [Archives]
  #1  
08-26-2003, 09:11 PM
audi2honda audi2honda is offline
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I read the faq and it says downmix will encode the center and surround channels, but it may not sound right on "non-prologic" systems.

I currently have just a regular HDTV, but no surround system (plan to get one soon though) Am I missing out on surround sound if I don't use downmix?

Sadly, I haven't used this in the last 10 or so backups I've made. Seems to me if I don't check it and only encode the R&L channels I'll be missing out on a lot of sounds from the rears?

Thanks
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08-26-2003, 09:19 PM
jorel jorel is offline
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audi2 honda my friend:
did you believe that i was thinking
and reading about this in exact moment?


see this....i was reading:
Q17: Should I check Dolby Surround downmix?
A: Leaving it unchecked will only decode the two main front channels, left and right. If it is checked, the center and surround channels will be encoded into the resulting wav file, but with 'pro logic' encoding. This may distort the audio somewhat when played back on a non pro logic capable playback system.

http://forum.doom9.org/showthread.php?s=&threadid=59272

i need more details!
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08-26-2003, 09:23 PM
audi2honda audi2honda is offline
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LOL that is exactly what I just read.

WOnder if kwag or anyone else has tried it. I wonder when encoding from AC3 to MP2 if you can still retain all these seperate channels?
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08-26-2003, 10:24 PM
kwag kwag is offline
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Well, I think the statement: "This may distort the audio somewhat when played back on a non pro logic capable playback system." is nonesense, because pro-logic signals are encoded on the audio channels at low frequencies. So they shouldn't make any kind of audio distortion.
Here's some reference:

"Dolby Pro-Logic Surround Sound:
Four channel surround sound process (Left/Center/Right and Surround). These four images are mixed into the Left Total and Right Total signals during encoding, permitting ProLogic signals to be embedded in, and ultimately read from a standard Left and Right channel stereo soundtrack. This process of encoding four channels into two carriers, ( Left and Right ) and retrieving them as 4 channels on the decode side is referred to as 4-2-4. The defining element of ProLogic is that it utilizes active decoders to localize dominant audio tracks (to position them correctly within the 360 degree sound stage in accordance to their proper established amplitudes) through the use of a high separation decoder processing. Frequency response of the rear channels is limited to 100hz to 7,000hz to eliminate crosstalk and sibilance errors between the center channel and rear surround. Low frequency non-directional signals (20-120) are generally routed to a subwoofer for reproduction."

Edit: I encode everything as "Dolby Prologic II (DS2)", and never had a problem in DS2 receivers, or plain stereo receivers.

-kwag
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08-26-2003, 10:30 PM
audi2honda audi2honda is offline
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Thanks Kwag,

So are you saying i should use downmix in dvd2avi. Then in HeadAC3he I should use dual channel, surround sound 2, 2 channels? or can I do 4 or 6 channels?
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08-26-2003, 10:40 PM
kwag kwag is offline
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Quote:
Originally Posted by audi2honda
Thanks Kwag,

So are you saying i should use downmix in dvd2avi.
No. You use "Demux" ( NOT Decode ), to extract your AC3 audio "untouched". I never do downmix with DVD2AVI.
Quote:
Then in HeadAC3he I should use dual channel, surround sound 2, 2 channels? or can I do 4 or 6 channels?
Yes, but you use 2 channels, as the surround information is encoded in the left and right channels. It's a function of the receiver to separate the surround carrier signals, decode them, and give you Dolby Surround audio.

-kwag
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08-26-2003, 10:44 PM
audi2honda audi2honda is offline
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awesome thanks kwag. Last question. If I have extra room can I just mux the ac3 file for my KVCD or should I still convert it to mp2?
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08-26-2003, 11:25 PM
kwag kwag is offline
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Quote:
Originally Posted by audi2honda
awesome thanks kwag. Last question. If I have extra room can I just mux the ac3 file for my KVCD or should I still convert it to mp2?
VCD/SVCD specifications don't support AC3 audio
You must encode to MP2.
Unless you wan't to play your KVCD's on your computer, or maybe on a Cyberhome DVD player or such, which supports RAW mpeg files
Then you probably can mux your KVCD MPEG1/2 stream (Note: No (X)VCD there at all ) with an AC3 stream, and enjoy superb audio

-kwag
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04-30-2004, 05:44 PM
Zanny Zanny is offline
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Quote:
Unless you wan't to play your KVCD's on your computer, or maybe on a Cyberhome DVD player or such, which supports RAW mpeg files
offtopic i have a cyberhome so what do you mean by raw mpeg?

literally just burn a .mpeg file to disk and it will play?
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04-30-2004, 06:02 PM
kwag kwag is offline
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Quote:
Originally Posted by Zanny

offtopic i have a cyberhome so what do you mean by raw mpeg?

literally just burn a .mpeg file to disk and it will play?
Exactly
Just burn the mpegs as "data" mode. Not as VCD/SVCD mode-2.

Edit: Just remember that you'll fit less data, because of the extra CRC data that is used on MODE-1 (data mode).

-kwag
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