How to Normalize avi Video Files
By Joseph Schembri

Many times when I have created a DVD from an Avi File and played it on my TV, I would have to raise the TV volume almost all the way to maximum in order to hear the actors. Then when the action switched, the TV would blare out and almost make me deaf so I would have to lower the volume. Of course for quiet scenes I had to raise the volume again. This started to get very annoying. I told myself there had to be a way where I could normalize the AVI and have the volume level at typical TV volumes so that I would not have to constantly raise and lower the volume depending on what part of the movie I was watching.

I had the similar problems for my mp3 music files but I was able to equalize these so that they all played at the same volume when I played the CD in my car or audio system. The volume from an AVI file cannot be treated the same as a mp3 music, as the AVI has a much wider range of sound. AVI sound can go from very low to very high where mp3 volume tends to be at a more steady level.

To see if I could do something similar, I performed an experiment with an AVI file, that when I created a DVD, had this very low volume causing the TV volume to be cranked up and cranked down constantly.

The following were the software programs I used.

1) Audiograbber 1.83 by Jackie Franck
2) MP3gain by SourceForge
3) Normalize-0.253 by Manual Kasper
4) Pers-o-FrontEnd 4 Normalize Gui for Normalize-0.253
5) Pazera Audio Extractor
6) AVIcodec

All the above software are free for download. Just Google and find. The first thing we need to do is to find out what type of audio file is in the AVI. We do this by running the AVIcodec program. We select the AVI in question and then click on it in the program to see its characteristics.

In an AVI the audio is typically mp3 and can be either of the following:

1) Bit rate of 128 kbs, Sampling frequency of 44,100 hz and Channels 2-stereo, or
2) Bit rate of 128 kbs, Sampling frequency of 48,000 hz and Channels 2-stereo

The first thing we do is extract the audio file from the AVI using Pazera. We extract one audio file as a PCM wav file. We then extract the audio file again but as an mp3 file. The mp3 file is typically the audio that is encoded in the AVI vedio file. If the mp3 file is sampled at 48000 hz then you need to extract it first at 44100 hz as that is the way audiograbber expects the wav file to be.

We rename the files as:

1) TestPCM.wav for the PCM file
2) TestMP3.mp3 for the mp3 file

We now open Audiograbber and enter the normalize window. We input the 44100 hz PCM wav TestPCM.wav and then press the test button to see its peak and average (volume) value.

The following were the results:

Peak Value: 77.77
Average Value: 13.68

By mp3 volume standards the average would be considered to be on the extreme low side. We now open the MP3gain program and input the mp3 file TestMP3.mp3 and perform a track analysis which gave:

Volume: 82.6

Since this had been converted to a DVD, it appears then that if the mp3 extracted audio file has a volume of 82.6, then this can be considered too low for normal DVD conversion.

We now run the Pers-o-frontend GUI and input the 44100 hz TestPCM.wav file. We use the -m parameter at 100% to set all peak audios to 100%. To get 100% the program indicated it had to use a gain factor of 2.184 dB

We now use audiograbber and input the -m modified TestPCM.wav and do a test run which gave the following:

Peaks: 100
Average: 17.58

We see that even with audio peaks all set to 100%, the volume was still on the low side. I have found that applying a gain of about 12 db always seemed to give good volume levels. Since the -m option applied about 2 db of gain, then we only need to apply a gain of 10 db to the modified TestPCM.wav to increase its overall volume. We run the Pers-o-frontend GUI and again input the -m modified TestPCM wav. This time, however, we choose the -a option at 10 db. Now we run Audiograbber again and this time input the -a modified file and do a test run.

The following values were now shown for the -m and -a modified TestPCM.wav file:

Peak: 100%
Average: 53.09

We see that the Average (Volume) level increased dramatically and is within a good volume level. Now we run Pazera again and convert the -m and -a modified TestPCM.wav file to an mp3 file. We run MP3gain and input this new modifed mp3 file and do a track analysis which gave:

Volume: 94.4

The MP3gain showed a volume increase from 82.6 to 94.4, about 12 db of gain which agreed with the 2.184 db peak gain and 10 db amplification gain.

The AVI file was then coverted to DVD using the -m and -a modified TestPCM.wav as its input audio which would automatically replace the audio that the AVI was made with. When played on the TV, audio volumes were quite uniform and within the average TV volume levels. This was a dramatic improvement over converting the AVI file with the audio it was made with.

We can now summarize the correct procedure to Normalize the AVI file prior to DVD conversion.

Step 1:

Using Pazera, extract the audio file first as an mp3 file, which is what it normally should be.

Step 2:

Using MP3gain, do a track analysis to determine the volume level.

a) If the volume level is around 82 then proceed to Step 3.

b) if the volume level is around 92 db or higher then do the following:

i) Using Pazera, extract the audio as PCM wav, sampling frequency does not matter

ii) Using the Pers-o-frontend GUI, modify the PCM wav with only the -m 100 option

iv) Convert the AVI to DVD using the -m modified PCM wav as the video audio source.

Step 3:

i) Using Pazera, extract the audio again as a PCM wav, sampling frequency does not matter.

ii) Using the Pers-o-frontend GUI, modify the PCM wav with only the -m 100 option. Take note of the gain that the program uses to increase the peaks to 100%, say x db.

iii) Still using the Pers-o-frontend GUI, input the -m modifed PCM wav but now switch to the -a option set for a gain of (12-x) db.

iv) Convert the AVI to DVD using the -a modified PCM wav as the video audio source.

So far this AVI normalization method has worked quite well creating good DVD volume levels.

Joseph Schembri has written many ebooks that are practical, easy, but thorough with step by step advice on website security protection, internet niche marketing and video and audio solutions. They are written in a language that you can understand with all the extra nice to have stuff stripped away.
http://www.schembrionics.com
http://www.websiteprotection.net

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