Audio Compression

[gs0666]

Now then....
Last time I asked about Cutting Avi's in Virtual Dub so I can fit the file on a cd.

Say I have a file that's allready been cut (including end score) and it's still too big.
How about recompressing the audio???
Is it possible to chop a couple of Megs of the file?
If so,what format should I use ??

[setarip]

Sure you can - in VirtualDub once again. Load your file into VDub. Make certain that you reset "Video" to "Direct Stream Copying". Change "Audio" to "Full Processing Mode"and click on "Conversion". Select a lower frequency (44,100 instead of 48,000, or 22,050 instead of 44,100, etc.). Click on "Conversion". Select the format that was originally used (frequently, .MP3). If the window to the right remains blank, select "Show all formats". Select a lower sampling rate from within the list of those at the newly picked lower frequency (e.g. If you changed to 44,100, choose ONLY from among the 44,100-related sampling rates). Save your file with a new name.

Let us know of your success ;>}

[gs0666]

Thx setarip.It worked like a dream....again.
Now it's time to find the proper format

[gs0666]

Uhhhhhhh.....
One problem.
The audio goes out of sync about half way into the movie???
Is there a way to fix this?

[benderman]

Changing the sample rate won't do anything for the size (only if you save as raw WAV/PCM). You can keep the 48kHz, change "Audio" to "Full Processing" and select the MP3 format. Then you should see a list of available bitrates. The lower the bitrate is the smaller gets the file. For stereo-sound you need at least 96kbps for good quality (128kbps is near CD).

An example:
If you have an 90min-movie with 128 kbps-sound and you reduce it to 112kbps the new movie would be about 10.5 MB smaller tham the original.

Formula:

time in sec*(original bitrate-new bitrate)/8=saved space in kilobyte

[gs0666]

Thx ,but I know that.
My problem is the audio sync problem after I've converted

[setarip]

"The audio goes out of sync about half way into the movie???"

Nothing in what we've done heretofore should cause that to happen. Are you certain that the ORIGINAL file was in synch (no pun intended) for the entirety of the video?

[tomnhanni]

I'm curious to know what bit rate you've used. Because anytime I've used a bitrate lower than 96kbps I had a/v sync problems. Also Divx audio codec produced a/v sync for me at 64kbps. Also I would be sure to use the oficial MP3 codec and not a hack for best results. Also there is a 'Sync to Audio' setting in the options tab in Virtual DUB I'm not sure what it's for but make sure it's checked to be sure.

[gs0666]

I tried watching the movie to find out where the sync problem lied and.....
There's some corruped frames in the middle of the movie so I think that's where the sync prob lies,but there was no frame problems before I converted the audio.
I use DivX AntiFreeze to prevent the movie from stooping when I hit a corrupt frame,and ....you know .....the weird colors and stuff.
Hmmm I deleted the original,so I'll have to D/L it again and try over.I will convert some other movies.I'll get back to you on this issue later.