audio noise reduction

[khobar]

I'm interested in reducing the audio noise level in my captured video I'm working on. I captured using a WinTV card and virtual dub, and it made 10 segments of about 2GB each. I then converted each segment using TMPEG to first SVCD and then VCD. When I was done with all 10 segments, I used the cut/join function to make one lone MPEG2 file which I then cut into two MPEG2 files and burned my SVCD's from those files. The VCD was only one MPEG1 file. I'm quite pleased with the results all around except for one thing: there is excessive hiss in the audio.

Starting with the VCD since it's a bit easier to work with, I demuxed the source .mpg file into the video and audio components. I then converted the mp2 audio to .wav and imported this into Cool Edit 2000. The beginning of the audio had only the noise so I used that as my base and applied the noise reduction to the entire audio track. The results were shocking! All I had to do then was adjust some treble and I had what I considered an outstanding audio track.

The Problem: remuxing the .wav file with the MPEG1 video stream using TMPEG doesn't work, it won't allow it. I tried Cool Edit and GoldWave to export the audio back to .mp2 format but neither did the job. I ended up using an mp3 encoder which TMPEG took. Now I was able to produce a VCD with outstanding audio compared with the original, but I am uncertain is using mp3 was a good idea.

On my own computers it works fine. On my wife's NT laptop it plays the video but no audio. I'm concerned that the audio won't play on any system that does not have an mp3 decoder. The goal is to produce VCD's to send out to friends and relatives, that sort of thing, and I want them to be able to play them.

Is this a real concern or is NT the problem?

Thanks,

Paul Nixon

[cycletron]

I too am interested in this. Anyone???

[ebaldino]

Yeah, this is exactly what I´ve been trying to do too.
I´ve been using DCLive; Great program, but after removing the hissing (by sampling) there´s a little bit of sound artifacts left on the background... not too much, I´m sure a lot of people would be willing to live with it...
But I would like to find and try other options...

rgds
E.Baldino

[vitualis]

khobar,

You've done several steps that would have been done much better in other ways.

Firstly, joining MPEG files (MPEG-1 or MPEG-2) is generally a bad idea. If you are lucky, all you will have is a slight blip, but as you are introducing streams errors, you can also have problems with the mpeg stream hanging at those points or a loss of A/V sync.

All joining should be done in the AVI stage. Cutting is usually less of a problem (especially for CBR MPEG, but can still be an issue if you use VBR -- i.e., SVCDs).

It is quite easy to have TMPGEnc encode all the AVI segments into one large mpeg (the whole movie that you can then cut, or encode each half of the movie on their own). All you have to do is to load up the AVI segments with VirtualDub, and then frameserve to TMPGEnc.

As for the audio, it is obviously detrimental to go frome WAV --> MP2 --> WAV --> MP2 again to remove the noise. This leads to a generation loss of quality.

You can use VirtualDub to load up the above AVI segments and then output the audio to WAV. Then, do your noise reduction and save it as a new WAV file. Then, with Virtualdub still on the same project, have it load the new WAV audio rather than use "AVI audio". Frameserve to your favourite encoder.

If you already have the MPEG video stream and want to remultiplex a new audio into it in WAV format, you must first encode it to MPEG-1 Layer2 audio at 224kbit/s. All common MPEG encoding tools can do this (e.g., TMPGEnc, Panasonic, Xing, LSX, etc.) A good option is to use the toolame plugin with TMPGEnc. This yields much better audio quality than the native TMPGEnc audio encoding.

Once you have your MP2 audio file, you can multiplex this with the original video. Use the TMPGEnc MPEG Tools or bbMPEG to multiplex (with TMPGEnc, make sure you set it on "MPEG-1 Video-CD" rather than "MPEG-1 Auto".

You cannot use MP3 audio on a VCD.

Regards.

_________________
Michael Tam

<font size=-1>[ This Message was edited by: vitualis on 2001-09-19 07:37:48 ]</font>

[khobar]

Michael,

Thank you very much for the info. I'm new at this and appreciate your indulgence. I will do what you suggested and see what happens. I've not used the frameserver function in VirtualDub but I have read a little about it. Now's my chance to gain some experience.

Thanks again,

Paul