Tuesday, 13 March 2007 11:37
Frequently we come upon avi files with sound whose volume diverges from the usual norm. Either it is too strong in which case our speakers choke up.
VirtualDubMod
MP3Gain
Extra hard disk space equal to the original avi file size + some more for the new audio file (to be exact: 0,00732421875 MB per minute per Kbps of the mp3's bitrate)
1. Checking the audio format
we answer "No". Our file will be opened. Then we select File -> File Information:
Here, we watch out for the "MPEG-1 Layer 3" indication, which means that our file has indeed an MP3 audio stream
making the attempt viable. We close the AVI Information window.
We select Video -> Direct Stream Copy and then access the Available streams window as above. We now double click on the initial audio stream (causing it to change color as in the following screenshot), then click on "Add":
5. Checking the new avi with the software player of our choice.
Remarks:
Section 3 can be also applied to our collection of MP3 files, if we would like to normalize their volume to a uniform level. In MP3Gain, we just click on the "Add Folder" button and proceed as usual. If many files are selected, bear in mind that the analysis process can take extremely long to complete.
Eusebius, for his suggestions in my first tutorial written for Insomnia and proposing OptiPNG for compressing the images of the the on-line version.
We shall need:
VirtualDubMod
MP3Gain
Extra hard disk space equal to the original avi file size + some more for the new audio file (to be exact: 0,00732421875 MB per minute per Kbps of the mp3's bitrate)
Procedure:
1. Checking the audio format
We execute VirtualDubMod, then selecting menu File -> Open video file... (CTRL-O) -> we open the avi file in question.
If the following dialog appears:
If the following dialog appears:
we answer "No". Our file will be opened. Then we select File -> File Information:
Here, we watch out for the "MPEG-1 Layer 3" indication, which means that our file has indeed an MP3 audio stream
making the attempt viable. We close the AVI Information window.
2. Demultiplexing the sound into an MP3 file
We select Streams -> Stream list:
If our avi file does not contain a second audio track (a rare case) the only audio track will be selected by default here. We select "Demux" and in the following dialog we choose a filename for the new MP3 file that will be generated, e.g. audio.mp3". After clicking on "Save" and depending on the avi file size, our hard drive's speed, whether we save on a different physical drive (not just partition) than the one from which the file is being read, the process will take from half up to 2+ min. When it is finished, we just close the Available Streams window.
3. Calculating the volume level and correcting
Without closing VirtualDubMod, we execute MP3Gain. In the Options menu we must make sure that the "Don't clip when doing Track Gain" option is enabled:
Following, in the "Target "Normal" Volume" field:
we enter the level of our choise. The default value of MP3Gain is 89 dB, which is rather conservative. I personally choose 92 dB but in the ears of others this is still considered low. In any case, I strongly propose not to exceed 95 dB. We now click on the large "Add File(s)" button, open the mp3 file that was created earlier and then click on the "Track Analysis" button. The analysis process is very CPU+RAM intensive and for large files some patience is required. The test mp3 file (116Kbps VBR, 1h59m27s, 99MB) took 1m40s on an Athlon XP 2400+/512MB RAM 170MHz DDR system. When it is over, we take a look in the results:
A very short explanation (with info taken from MP3Gain's help file):
- The "Volume" column shows the current mean volume level of the file in dB.
- The "clipping" column shows "Y" when the volume reaches a high level. Sometimes this can manifest in the form of scratching sounds during playback.
- The "Track Gain" column shows the delta (difference) in dB that must be applied to the file in order to reach the volume level specified in the "Target "Normal" Volume" field. It does not always equal to "Target Normal Volume minus Volume", because the mp3's frames cannot take continuous volume values, only discrete.
- The "clip(Track)" column shows "Y" when the application of the previous delta will cause a clipping effect to the file. That is why we have already forbidden this, by enabling the appropriate item in the Options menu.
Some comments of my own:
The "Volume" column is already giving us an indication of the problem with our file. If we see a value greater than, say 100, this will be translated into the characteristic choking of our speakers during playback. If we see a very low value (e.g. <80, I have come upon as low as 20-30!) this means that the sound will be hardly audible. Now, by clicking on the "Track Gain" button the file will be subjected to the maximum possible dB delta which does not cause a clipping effect. In some rare cases, this will lead to œVolume to low, impractical values, therefore it is preferable despite clipping, to disable the "Don't clip when doing Track Gain" from the Options menu, then repeat the process and reenable the above option for future use. In the test file, by clicking on the "Track Gain" button I had the following results:
i.e. the volume level was lowered! By making the appropriate change in the "Options" menu and repeating:
which is a more logical value. We close MP3Gain and switch back to VirtualDubMod.
4. Multiplexing the new audio file into the avi
We select Video -> Direct Stream Copy and then access the Available streams window as above. We now double click on the initial audio stream (causing it to change color as in the following screenshot), then click on "Add":
We choose "audio.mp3" and if the question dialog described in section 1 appears, we answer "No" again and click on "OK" to close the Available streams window. Following, we select File -> Save As... (F7) and save our new avi in the directory of our choice, with the following adjustments:
We can now close VirtualDubMod.
5. Checking the new avi with the software player of our choice.
Remarks:
Section 3 can be also applied to our collection of MP3 files, if we would like to normalize their volume to a uniform level. In MP3Gain, we just click on the "Add Folder" button and proceed as usual. If many files are selected, bear in mind that the analysis process can take extremely long to complete.
The following F.O.S.S. (Free and Open Source Software) was utilized for the creation of this tutorial:
Thanks goes to :
Eusebius, for his suggestions in my first tutorial written for Insomnia and proposing OptiPNG for compressing the images of the the on-line version.
Originally created for: insomnia.gr
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