Audio levels too low after using dvd-decrypter.

[h0mi]

I've ripped some episodes of the boondocks from my dvd, but it turns out that the audio levels are low, so converting it to psp video results in audio levels that are just too low. I guess I can either increase the audio levels in the vob files or in the mp4 files I have (the source audio appears to be the problem) but I'm not sure which is easier or what software exists to do the job.. I'm aware if I had ripped to an avi container, I could use virtuadub to extract a .wav file, and then edit the .wav with audacity but I'm not familiar with identical tools/process for editing dvd(vob) or mp4 files. Suggestions?

[guns1inger]

The first thing to point out - DVD Decrypter does not change the audio levels when it rips. It is a file copy program. The levels should be the same as when the files where on the disc. If they don't appear to be, the first thing to look at is the playback programs and decoder settings. This is especially important if the audio is AC3.

[Soopafresh]

Totally. AC3 decoders and volume control settings is a science in itself. As most home PC users only have a 2 or 3 piece speaker system attached to their box, there's a lot of volume compensation that must occur. You could run a program that measures the loudest parts of the AC3 file on the disk vs the AC3 ripped to your hard drive and they'd end up being the same, because they are the same.

[h0mi]

So it sounds like the source video has low audio levels, so all dvd decrypter does is copy it verbatim. Should I edit the vobs and up the sound level, or the resultant mp4 files created by pspvideo9? And to do either, what tools will do the job?

[Soopafresh]

Just Use AC3Filter to boost your playback on the PC - http://ac3filter.net/

[guns1inger]

AC3Filter can also be used to boost the volume when converting to other formats

[h0mi]

I must be missing something. I installed AC3Filter and configured some settings to increase the gain but when I try to convert the vob to mp4 using pspvideo9, there's no increase in audio at all.

[Soopafresh]

Oh........you wanted to convert the files. Gimme a minute to dig up the info.

Question:

Do you give PSPvideo9 only 1 VOB to encode ?

[guns1inger]

Used to software that uses AC3 Filter to decode AC3 audio. It will affect these programs. If PSPVideo9 has it's own AC3 decoder then it will ignore any settings in AC3 Filter.

[Soopafresh]

Yeah, it uses ffmpeg. Working on a script right now to normalize the audio. I'll post it shortly

[Soopafresh]

Here you go Took a while to find a reliable combination of demuxer/muxer. This script will make your audio very loud for conversion and won't touch your original .VOB files if you don't like the results. Place the contents of the Zip file into the same folder as your VOBs and double click
_Run_VobGain.bat to run. It'll take 5-10 minutes per VOB and will create output files with .MPG extensions to feed into your PSP encoder app. It works pretty well. I'm going to use it myself.

Make sure you have some free disk space on your drive - 2-3X the amount of space that the VOBs occupy. Listen to the volume difference between file1.vob and file1.mpg

http://www.bestsharing.com/files/CgJosk2226652/VobGain2.zip.html

[h0mi]

Thanks for the help. So I downloaded vobgain, and ran it after copying 1 of the vob files to the vobgain directory (since it's using a .bat file to operate).

I can't seem to find the resulting mpg file. There's a temp.vob file but no mpg one.

[Soopafresh]

Lemme test it...



EDIT - Okay, New Version. Use this one instead.

http://www.bestsharing.com/files/lxfiJFc230647/VobGain3.zip.html

[h0mi]

Ran the new bat file and same thing... no .mpg file is being created or kept. The temp.vob file gets deleted when its done.

[Coises]

If you're up for an experiment, I recently wrote a program to solve a similar problem for myself. It may or may not work for your case.

The program, VOBDNorm, copies a VOB and changes the "Dialog Normalization" value of AC-3 audio in the VOB. If the program you're using to convert the DVD to PSP video respects the dialnorm meta-data, and if the DVD has clean AC-3 audio to begin with, just a dialnorm setting that makes the volume too low for good transcoding, then running this program against each VOB ripped from the DVD before converting may help.

The link above is to a zip archive; it contains a Windows command line executable and the C++ source for the program. Just extract the vobdnorm.exe file, open a DOS window, and use a command something like this:

"path-to-exe\vobdnorm.exe" "input.vob" "output.vob" 31

on each VOB (don't make the input and output the same file!). If you see that the program says it has changed dialog normalization values of, say, 25 or less to 31, then try converting the results. (If your program converts whole DVDs, make the output files have the same names as the input files but in a different folder; then copy the other, non-VOB files into the same folder.)

(In practice, a dialog normalization value of "31" means "don't compensate for overall volume at all, just decode the AC-3 and pass it along full scale. Higher values are not possible; lower values attenuate the output by 31-dialnorm decibels. Depending on the decoder, however, compression also may be applied, and changing dialnorm can mess that up.)

If you try this, I'd appreciate any feedback you can give about your experiences with it.

[h0mi]

The bat file seems to have a problem here:

mplex -f 3 -s 2048 -h -V -v 0 -b 896 -o "VTS_04_1.mpg" x.lpcm x.demuxed.m2v
**ERROR: [mplex] Unable to open file x.lpcm for reading.

x.lpcm is not getting created.

[h0mi]

Ok I attemped to run the vobdnorm application. When I ran it with oldfile/newfile 31, the sound did not increase in the new vob file, leaving me where I was at the beginning.

[Coises]

Ok I attemped to run the vobdnorm application. When I ran it with oldfile/newfile 31, the sound did not increase in the new vob file, leaving me where I was at the beginning.

I'm sorry it didn't help. Did you notice whether there were any lines in the console output like this:

Dialog normalization modified in 4354 frames in AC-3 sub-stream 0:
       Changed 18 to 31 in 4220 frames.
       Changed 23 to 31 in 134 frames.

If there weren't, then either the dialog normalization was already 31, or my program is malfunctioning (quite possible, since it's had very little testing yet). Do you have a copy of VobEdit around? If so, you might check a few AC-3 packets in the original VOB and see what the Dialog Normalization is. If it's already 31 then VOBDNorm won't help. If it's not 31 and there were no "Changed" lines, then VOBDNorm is malfunctioning.

If there were "Changed" lines but it didn't make any difference, it may be that the change was too small (e.g., it was already 30, or it was 0, which is interpreted as 31) or that the program you're feeding the VOB into doesn't use that bit of AC-3 metadata anyway.

[Soopafresh]

BTW, Coises, I saw that your app has been mentioned on the Doom9 audio boards


h0mi - I wonder if it just makes sense to up the audio levels in your post converted target file.

[h0mi]

Soopa- perhaps... but I don't know how to do that for an mp4 file.

[Soopafresh]

Here's an example before normalizing (yeah, I know - I kept the bitrates way down)

input.mp4

Here's the file after Normalizing

output.mp4

Download
http://www.bestsharing.com/files/byhoqAb235068/mp4gain.rar.html

Since your files are for PSP, I'll try to make it easy for you

Doubleclick mp4gain.bat to process

1) The batch file will rename your original MP4 file to OLD-filename.MP4. The NEW one will be named with the original file name for compatibility. (Easy to see, hard to explain)

2) The remuxing process in ffmpeg includes the "-f PSP" parameter to ensure PSP compatibility.

3) I'm assuming you've been converting to H264 AVC MP4s for PSP (hee hee hee- more acronyms anyone? )- If not, no problem. Use the Xvid_MP4gain.bat instead for mp3 audio instead of aac.