How to exchange the L/R sound channel on the VCD MPEG1 files

[chrislau]

It may be a very easy question.

Can someone help me how can I exchange the Left / Right Sound channel on a standard VCD format (*.mpg/*.dat) files.

It is beause, I have many karaoke VCD file,the vocal is usuaily on the left channel , and the music is on the right channel. But I get some is music on the left channel and vocal is on the right channel.

So I want to reencode it than burn on the CD, and standardize the sound channel. (No need to change the L/R while singing karaoke)

Please tell me the most easy way and quaility no lost is first Priory.

Thanks a lot.

Chris Lau

[mats.hogberg]

The only way I can come up with (besides moving the speakers...) is to demultiplex the VCD mpeg, convert the audio mp2 track to wav, then swap channels with some audio editor, reencode the wav with swapped channels to mp2 then multiplex it with old video m1v again. This will give you some loss in audio quality, but probably not noticable. Video will be untouched.

/Mats

[deadpac]

@chrislau
Let me preface my solution by saying that the way I did it just now is with whatever tools I already had in front of me and that there is probably a more user friendly way of doing this. Also the way I chose to solve your problem was with 2 completely free (almost) tools. There's probably is one program that will do this for you in one fell swoop, but being that I am not an audiophile I couldn't tell you; hopefully if you don't like this solution then somebody else in the forum can post an easier way of doing this.

So if you have never used or don't care to try TMPGEnc and the dreaded AVISynth then you can just ignore this post altogether . I only really posted because I was bored and since I usually don't use AVISynth to process my audio; I thought it would be interesting to see if I could solve your audio problem with just an AVISynth script; and low and behold I did.

Assuming you have TMPGEnc and AVISynth installed

Here goes...
Step 1 - Load the MPG file as the audio source in TMPGEnc and export the audio as a WAV file by going to...
File > Output to File > WAVE File

Now comes the AVISynth script, just open up notepad and paste the following lines

#Step 2 - load the wav file
OrigAudio = WavSource("AudioFromVCD.wav")

#Step 3 - normalize the wav file
audio = Normalize(OrigAudio, 1.0)

#Step 4 - Switch the Left and Right Channels

left_channel = GetChannel(audio, 2)
right_channel = GetChannel(audio, 1)

#Step 5 - Merge the newly switched channels
Switched = MergeChannels(left_channel, right_channel)

Switched

Notes:
Step 2 - replace "AudioFromVCD.wav" with the location and name of the file you saved in step 1

What the script does is basically load the WAV file you got from step 1 in step 2 and then in step 3 it normalizes the clip for you. Now step4 accomplished what you wanted the switching of channels because according to the AVISynth documentation 1 is defined as the left channel and 2 as the right channel; in step 4 the script defines the left channel to actually take the right channel and vice versa for the right channel definition. And in step5 the script brings it back together by merging the channels back together again. The script calls Switched at the end so that the script actually outputs something; wouldn't want to do all that work and basically have the script do nothing

Save the avs script in notepad making sure you save with either double quotes " on each end of the filename "likeso.avs" or use the Save as Type bar and make it All Files.

Open up the avs script as the audio source in TMPGEnc and encode as elementary stream with VCD audio specs, you know Stereo 224kbps@44k and you should then come up with a new MP2 file. Use TMPGEnc's MPEG Tools and just MUX the video from the original MPG file and the new mp2 file you just created and you should be good to go.

Trust me this is actually easier than it sounds/looks. Also the video is untouched and the audio should come out with almost no loss in quality.

If this solution is not for you then hopefully somebody else should have a one step solution for you, I think. Maybe something in Premiere, GoldWave, SoundForge, ........etc

[chrislau]

deadpac

Thanks very much for your detail explain.

I'll use your method and try.

Thanks in deep.


If someonelse has another method (more easy step)

Please give me a hand here.

(because I need to convert more than a 50 files)

[deadpac]

@chrislau

No problem but yeah my method probably isn't too efficient if you're going to be doing a mass conversion. I didn't know how many files you wanted to do so I was just going by what was in in your initial post.

good luck with that

[chrislau]

deadpac

Thanks you , you are a nice guy here.

I've try your method, it works and all process take me ~ 5 min. to convert 1 file.

But the output files size is smaller than the original one.

I've checked that the video and audio quality is the same. (I burn the file and play on my hi-fi to check)

Do you know why?

Again, thanks for your graat help.

Chris Lau

[deadpac]

@chrislau

Only thing I can think of off the top of my head is bitrate. Did you use 224kbps bitrate @44khz when you encoded the file.

I don't think there should be a problem if it plays fine on your standalone player.