Equalize Volume from Damaged Tape Capture

[Janusian]

I did a capture of a VHS tape. The tape had been chewed by a VCR and had had to be rebuilt. As a result much of the sound was slightly muffled but audible, which would be fine. However the sound also occasionally jumps to a very high level, so that it almost sounds distorted. It lasts for less than a second in most cases, but obviously is very annoying. The file is now in MPG format, captured using the Compro software that came with the card, is there any easy way to smooth out the audio level?

[FulciLives]

Well you probably have a single MPEG file so you need to demux aka demultiplex the file. That is a process that splits the single MPEG file into two separate files: one a video only file and one an audio only file.

At that point you can then do whatever you want with the audio file and then worry about muxing it aka multiplexing it later (the process of making it a single file again ... often done during the DVD authoring stage assuming a DVD is your final product).

As for the audio editing ... you could try Audacity which is freeware audio editing program. First though you want to make sure you convert your audio to standard PCM WAV format first. Chances are it is now AC-3 or MP2. So that would be the first thing to do after the demux ... convert to PCM WAV.

After that you can play around with Audacity. As for that ... I'll leave it to someone with more experience. In other words I'm sure someone else will chim in with more info on how to actually go about doing the audio "editing" to "fix" your audio issues. That part is beyond me as I never had a source with your issues.

As for the demuxing ... I would use DGIndex ... as for the conversion to PCM WAV ... there are several ways to do that ... in fact you should be able to load the audio into Audacity and save it out as a PCM WAV file. I think Audacity will read MP2 files but I don't think it will read AC-3 files. For AC-3 to WAV I use a program called GoldWave which is trialware software. In fact GoldWave is probably the better choice (than Audacity) but GoldWave is trialware which means you can use it ... full featured ... for "X" number of "times" before it locks up and requires you to purchase a key so you can register it. The benefit? It can read AC-3 very well (assuming the original is 2 channel or 1 channel but not more than 2 channel).

- John "FulciLives" Coleman

[Janusian]

Thanks - I will give it a go this evening.

[redwudz]

Audacity can read WAV, AIFF, Ogg Vorbis, and MP3 files. I think that's all. Definitely not AC3. You can use 'Normalize' to set the audio to a standard level.

VirtualDub Mod, among others, can save out the audio from most formats as a WAV file: https://forum.videohelp.com/topic280779.html But you'll have to use something else to mux it back with the video or convert it to MP2 or AC3.

I use ffmpeggui for AC3 conversion. Then I use the authoring program to mux the audio back with the video.

[Janusian]

Audacity can read WAV, AIFF, Ogg Vorbis, and MP3 files. I think that's all. Definitely not AC3. You can use 'Normalize' to set the audio to a standard level.

VirtualDub Mod, among others, can save out the audio from most formats as a WAV file: https://forum.videohelp.com/topic280779.html But you'll have to use something else to mux it back with the video or convert it to MP2 or AC3.

I use ffmpeggui for AC3 conversion. Then I use the authoring program to mux the audio back with the video.

I have VirtualDub Mod, and am vaguely familiar with it, so I will give that as go.

When it comes to adding it back in, if I use something like Adobe Premiere is there a chance the two will be out of sync by the end?

[Janusian]

Well that took a while.

• I used VirtualDubMod to remove the Sound into a separate file
• Then used Audacity to lower the volume of the whole soundtrack
• Then used Audacity again to lower the volume of the distorted bits even more. This has to be done by hand.
• Then used Media Monkey to convert the Wav format into MP3
• Then back to VirtualDubMod to convert the whole video file to DivX, which I will now add onto DVD.

I suspect I will have lost some of the picture quality through all this, but at least the soundtrack is now at a level where it doesn't assault your ears. This is a wedding video, so the quality was always less important than being able to hear what was said.

Thanks for all the advice given, it was appreciated!