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Topic: HELP: best downmix to mono method (Read 10313 times) previous topic - next topic
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HELP: best downmix to mono method

I need (for my thesis) to convert a CD-quality file to a mono/32 KHz file, then compress it with Vorbis (aoTuV ß3) @ about 64 Kbps. I need to reach the best possible quality, so here what I (actually) do:

1. CD rip (EAC/aspi)
2. Remove phase shifts between left and right channel (Advanced Audio Corrector)
3. DC Offset adjust (Goldwave)
4. Resample -> 32000 Hz (wavefs44)
5. Downmix to mono (Goldwave)
6. Volume normalization (Foobar/replaygain)
7. Encode to Vorbis q3 (Foobar/oggenc)

Any suggestion ?

Do you know a better way to get higher quality ?

Do you know any open/free software to replace Advanced Audio Corrector & Goldwave functions ?

ANY REPLY IS ***REALLY*** APRECIATED !!!

Thanks a lot !!!

HELP: best downmix to mono method

Reply #1 –
Perhaps a bit besides the point, but do you really need mono? At such bitrates Vorbis's stereo coding is very efficient, so using mono won't actually gain you much.

HELP: best downmix to mono method

Reply #2 –
I NEED mono (is not a bitrate related problem)

HELP: best downmix to mono method

Reply #3 –
Ok then.

I would check if not removing the phase shifts from the procedure doesn't improve the results.

Downmixing can be done with almost anything, including Audacity and Foobar.

HELP: best downmix to mono method

Reply #4 –
Quote
I NEED mono (is not a bitrate related problem)
[a href="index.php?act=findpost&pid=268235"][{POST_SNAPBACK}][/a]


With Winamp you can modify stereo wav files to mono wav files easily.

Winamp have a output plugin:
"Nullsoft Disk Writer plugin"

Open Winamp; after, Control+P, in the left menu you can choose:
Plug-ins--> Output plugins--> Nullsoft Disk Writer plugin

In the Bottom you click: "Configure" and choose "Convert to format":
PCM 32.000 Hz, 16 Bit, Mono. Choose Output directory to target destiny...
That's All !!

HELP: best downmix to mono method

Reply #5 –
Hey, guyz... wait.  I know that foobar/audacity/winamp/anyuknow do the downmix.

But I said: best downmix to mono method

I need a "scientific method" (remember that is for a thesis !): I based my method on the infos founded on this page and this other

Any other "simple" method is not acceptable.

Thanks again.

HELP: best downmix to mono method

Reply #6 –
The "downmix to mono" in all those are doing exactly the same thing: (L+R)/2

DC offsetting correction may be a minor gain. Normalization is not going to gain you anything. Why would it?? You're feeding this into a lossy compressor, not mastering a CD. If anything you just introduced another lossy step.

Removing the pase shifts is a totally subjective step.

For the downsampling, use SSRC (foobar) or another high quality resampler. I would very strongly disrecommend winamp for that.

If you need to do this "scientifically" you will have to come up with better material than those two sites (particularly the first, lol).

HELP: best downmix to mono method

Reply #7 –
Quote
For the downsampling, I would very strongly disrecommend winamp for that.
[a href="index.php?act=findpost&pid=268245"][{POST_SNAPBACK}][/a]


Why??

HELP: best downmix to mono method

Reply #8 –
From what I can see it uses the builtin windows resampler. There are far better alternatives if he wants the best possible quality.

HELP: best downmix to mono method

Reply #9 –
Quote
From what I can see it uses the builtin windows resampler. There are far better alternatives.
[a href="index.php?act=findpost&pid=268252"][{POST_SNAPBACK}][/a]

PROBABLY, but my question is... Is this "windows resampler" as bad that you disrecommend???

HELP: best downmix to mono method

Reply #10 –
If he wants maximum quality, yes. Enough threads about that here...

Doubt you'd notice it for playback, though.

HELP: best downmix to mono method

Reply #11 –
About resampler: i used wavefs44 due to this claim "It seems to receive high praising from experts next to SSRC."

Quote
DC offsetting correction may be a minor gain. Normalization is not going to gain you anything.


Means slightly better compression.

Quote
Removing the pase shifts is a totally subjective step


Effectively i don't know how mutch the final result could benefit from this...

Quote
If you need to do this "scientifically" you will have to come up with better material than those two sites (particularly the first, lol).


Suggestions ?

HELP: best downmix to mono method

Reply #12 –
Quote
Quote
DC offsetting correction may be a minor gain. Normalization is not going to gain you anything.


Means slightly better compression.


I don't see why. The only difference between the normalized and non-normalized data going into the encoder is that the normalized stream will have extra noise added. How is that going to help?

HELP: best downmix to mono method

Reply #13 –
Hi, after reading this topic I made a search in google about Advanced Audio Corrector.  The claims on the shareware sites that are hosting it are the same marketing hip:

"If during manufacturing of an audio soundtrack there is an analog stage (recording to a tape or to a gramophone disk in an analog mode). After coding to MP3, these distortions are heard as unpleasant high-frequency sounds. Advanced audio corrector allows to remove the phase distortions in high-quality audio files (WAV, 16-bit Stereo) before coding to a format MP3."

Since I'm planning in the near future to rip a lot of my vinyl records (and encode with LAME) I want to know if this claims deserve to be taken into acount or are just BS. Because this is the first time I hear about such thing. 
Sorry if I'm offtopic.

HELP: best downmix to mono method

Reply #14 –
For downmixing to mono you may consider also just removing one of the two channels. This will propably give better results if the source is mono anyway.

HELP: best downmix to mono method

Reply #15 –
Quote
About resampler: i used wavefs44 due to this claim "It seems to receive high praising from experts next to SSRC."
[a href="index.php?act=findpost&pid=268447"][{POST_SNAPBACK}][/a]


Oh, shit, man, that is just opinion I gathered at some not-really-reliable sites and threw at RareWares main page. It's not meant to be taken as gospel.

If it explodes in your face, don't come blaming me

HELP: best downmix to mono method

Reply #16 –
Quote
Quote
About resampler: i used wavefs44 due to this claim "It seems to receive high praising from experts next to SSRC."
[a href="index.php?act=findpost&pid=268447"][{POST_SNAPBACK}][/a]


Oh, shit, man, that is just opinion I gathered at some not-really-reliable sites and threw at RareWares main page. It's not meant to be taken as gospel.

If it explodes in your face, don't come blaming me
[a href="index.php?act=findpost&pid=270480"][{POST_SNAPBACK}][/a]


wavefs44 seems to be ok. In highest precision mode, the aliasing reduction is slightly better than SSRC fast. SSRC slow is still better though.

HELP: best downmix to mono method

Reply #17 –
I'm not sure if this is of any use (as I can't read it), but this is quoted by DSPguru as to why SSRC is "simply the best" in the BeSweet FAQ thread.

http://www.ne.jp/asahi/fa/efu/fsconv/fsconv_2.html

The charts do look pretty impressive.