44100Hz MP3 but half the size of 128kbit

[mctt]

Originally posted by MaTTeR
23) Why is my MP3 destination file downsampled to 32kHz or lower?


In latter versions of LAME(3.9x), it will automatically downsample audio for low bitrates(<128kbps)

I want to make a dual audio DivX 5.0/LAME ABR/Gknot avi with the english track as 128kbit 44100Hz. However, I want to have the Directors commentary as a file about half the size. Of course I need the second audio track to sychronise with the first. I understand that LAME is not the best to perform the resample so what method/command should I use to get for example a 64Kbit 44100Hz second LAME ABR track.

Also, please don't suggest I use Ogg Vorbis with an OGM container file because I have done this but just want a simple and fast option.

So, to sum up. How do I create a 64kbit (or half size) audio track at
44100Hz using Azid (I think) within Gordian Knot?

[sh0dan]

- I hade this profile for 80kbps 48khz stereo commentary (to fit the ordinary audio track). The trick is so give as compressible data to lame, thus only delivering a mono signal.

Change the resample to 44.1 khz, and perhaps add an SSRC conversion.

The _best_ way would be for you to:

Extract the sound to a 22.050 khz wave file (using Besweet). Manually compress the sound using "--alt-preset 64" and specifying "--resample 44.1". That will give even better quality.


"C:\apps\BeSweet\BeSweet.exe" -core( -input "f:\dune_complete.wav" -output "c:\temp\dune\dune_complete.mp3" -logfile "c:\apps\BeSweet\BeSweet.log" ) -azid( -n1 -s mono -c normal -g 10db -L -3db ) -ota( -G 1 ) -lame( -m j -a --scale 1 --abr 80 --resample 48.0 ) -profile( Twin Peaks commentary )

[mctt]

I will give it a go. Cheers for your help sh0dan.

[pacohaas]

the lame algorithms are set up to provide the best quality at the given bitrate, that's the reason for the downsampling. So by forcing a sample rate not recommended by LAME, you will end up with a lower quality mp3. I think the best solution here would be to encode as a mono file. if you start the mono encode at 64kbps and lame wants to resample it, you should stop the encode, resample usin SSRC, then encode that file in LAME.

[sh0dan]

That would be the best, yes, but I've experienced that using a two-channel AVI will have problems with this, and end up playing the second (downsampled) track at a wrong samplerate.

Therefore the point is to make the file as compressible for LAME as possible.
- Using joint-stereo, there is almost no penalty, when encoding a mono-track as stereo.
- Pre-filter out all high frequencies (above 16khz or even lower) will make the file much easier for LAME to compress without artifacts.

[mctt]

Thanks sh0dan and pacohaas

What I really am aiming for here is a way to get a half size (half of 128kbit) audio track that will be suitable to go along side the main audio track. There are a two critical things I really want:

1. Convenience
i.e most quick and easy possible. No setting up separately from the Gknot interface if possible.
I can already do this with Ogg Machine but do not want the hassle of coming back to set up for video again followed by an manual mux. The idea is if possible to set the whole thing up from Gknot and leave it overnight to create a complete .avi.

2. Volume Level
If there is a way that I can ensure the two tracks are the same volume to make switching during playback more appealing.
Getting the least artefacts or encoding it in the _best_ way come second to convenience and matching volume levels.

The answer would be almost as simple as --alt-preset 64 , but with 44.1khz to match the main audio file. Sorry if you have already answered this but both you guys are on a more advanced level to me.

Is this anywhere near close to what I am looking for?

-azid( -n1 -s mono -c normal -g 10db -L -3db ) -ota( -G 1 )

-lame( -m j -a --scale 1 --abr 64 --resample 44.1 )

To be put in the Transcoding Parameters part of gknot here:
http://www.pnex.co.uk/gknot_audio.png

Again sorry to dumb things down. I could do an 800mb XCD with Xvid and Ogg with two audio tracks instead but what I really want here is just a plain old 699mb file where the directors comments do not compromise the video quality too much.

mctt