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Old 14th August 2003, 01:06   #1  |  Link
ukb007
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Freeware 'stretch' and 'cbr>vbr mp3' programs

Hi, everybody.

1. Can you please suggest some good freeware programs that can STRETCH audio by factors such as 100.0020 % like in CoolEdit 2000 ? Four decimel places is important for my purpose. GoldWave does stretch, but by integral factors such as 99% or 101%. CoolEdit, unfortunately, is not freeware. I'm being encouraged to search this because of a very good Nicky Pages tutorial about Audio Synch problem at http://nickyguides.digital-digest.com/audio-synch.htm .

2. What program do I use to convert cbr mp3 into vbr mp3 ?

Thanks.

Last edited by ukb007; 14th August 2003 at 01:13.
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Old 14th August 2003, 01:38   #2  |  Link
mrlipring
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cbr > vbr = winlame.
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Old 14th August 2003, 04:37   #3  |  Link
pacohaas
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1. as nicky says, you should rather change the video rate than the audio when syncing the two, why do you want to stretch the audio anyways?

2. again, why? if it's already in CBR format, converting to VBR won't save you anything, it won't make it better quality(in fact it will be worse).
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Old 14th August 2003, 12:58   #4  |  Link
nimrodim
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well if you change the video frame rate - you will not be able to convert it to dvd/svcd later.
i was thinking of a new way to sync - by changing the audio sample rate instead to get audio/video sync. Then convert audio to desired sample rate.
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Old 17th August 2003, 04:16   #5  |  Link
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What did Nicky say?

Thanks, pacohaas.

I may be wrong here, but what I thought Nicky said in the tutorial is to open the AUDIO in CoolEdit and stretch it by an amount that one gets by using his 'Terabits AVInfo 1.2a' program. Nicky has also said that if you change the fps then you can't play the resulting file without a computer (but, of course, you'd need a computer to play a DivX .avi anyway).

As I said, I may be wrong, and if so, I am doing it all wrong, and need to be told the right way. But, funny, I have done it successfully with two movies already. And it gave very satisfying results.

Thanks again.

Last edited by ukb007; 17th August 2003 at 04:23.
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Old 17th August 2003, 09:14   #6  |  Link
pacohaas
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guess i read an older version of that guide. But yeah, if your only goal is to play the divx on your computer, it would be much less hassle to apply the frame rate change from within the aviinfo tool.
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Old 18th August 2003, 01:26   #7  |  Link
ukb007
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Thanks again, pacohaas. Thanks, nimrodim.

But what if I DIDN'T want to change the fps, or the audio samplerate. How, then, can I go about this synching business?

Here's an extract from what Nicky says:

"If we (change) the video framerate the movie will play correctly in Media Player and, in fact, on all PC players. But what if we were synching our AVI file not because it was a DivX movie but because we wanted to convert the AVI to Mpeg or SVCD etc? It is unlikely that the VCD we created would be in synch! This is because all VCD, SVCD and DVD files must be exactly 25 or 29.970 fps to play in a DVD player or a stand alone player! A framerate such as 25.998 will not work!

Other synching tools offer to change the audio samplerate instead. Changing the audio samplerate may be able to put the movie in synch just as effectively as changing the framerate. But again this causes conversion problems. A VCD, DVD or SVCD will only take 44100Hz or 48000Hz respectively. Feeding an encoder 11025Hz will almost always end up with synch problems!

For this problem Terabits AVI Info tool is the only utility so far that can offer a solution. Notice that, ...it offers a stretch amount."

This is where the question of stretching (or contracting) audio to a factor like 100.0048% (or 99.9960%) comes. Cooledit2000 offers this service. GoldWave does, too, but by integral amounts, like 99%, 101% etc.

I was, therefore looking for any freeware tool that can match CoolEdit2000 on this aspect.

Regards.

Last edited by ukb007; 18th August 2003 at 01:31.
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Old 20th August 2003, 21:31   #8  |  Link
Prosper
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Changing audio sample rate is exactly what you want to do. If your source is 44.1k, and you dropped every nth sample, and than played it ba ck at 44.1k, the sound would be shorter. there is a tool in doom9's download library that does this, I think it's called wave length adjuster. I'm too lazy to look and find the filename for you.


EDIT:
OK, so if you read the abouve, I guess that 'changing the sample rate' isn't what I'm describing, poor word choice I guess. We're talking about changing the overall number of samples

Last edited by Prosper; 22nd August 2003 at 05:37.
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Old 21st August 2003, 03:15   #9  |  Link
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Thanks, Prosper

May I quote from what Nicky said once again?

"Changing the audio samplerate may be able to put the movie in synch just as effectively as changing the framerate. But again this causes conversion problems. A VCD, DVD or SVCD will only take 44100Hz or 48000Hz respectively. Feeding an encoder 11025Hz will almost always end up with synch problems!"

The question is, how do we effect synchronization WITHOUT changing either the FRAME RATE of the SAMPLE RATE ?

Mr Nicky Pages has a solution, and it seems entirely logical. Can you please take a few seconda to read it above, quoted in my earlier post, and offer comments ? Or you can read his very illuminating article in the link I have provided in another of my posts a little further up.

Regards.
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Old 21st August 2003, 04:16   #10  |  Link
pacohaas
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yeah, i know exactly what you're talking about. Haven't replied because I haven't seen any freeware programs that will do this. The only thing close to this that I know of is Amazing Slow Downer. Haven't really used it much, so sorry if it doesn't work out, but it's worth a try(trial version), but i don't think you'll get the precision of cooledit, and you're actually looking for more precision...tough question you have here.
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Old 22nd August 2003, 03:05   #11  |  Link
Prosper
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Re: Thanks, Prosper

Quote:
Originally posted by ukb007
May I quote from what Nicky said once again?

"Changing the audio samplerate may be able to put the movie in synch just as effectively as changing the framerate. But again this causes conversion problems. A VCD, DVD or SVCD will only take 44100Hz or 48000Hz respectively. Feeding an encoder 11025Hz will almost always end up with synch problems!"

The question is, how do we effect synchronization WITHOUT changing either the FRAME RATE of the SAMPLE RATE ?

Mr Nicky Pages has a solution, and it seems entirely logical. Can you please take a few seconda to read it above, quoted in my earlier post, and offer comments ? Or you can read his very illuminating article in the link I have provided in another of my posts a little further up.

Regards.
Dude, please read my post more carefully. I'm not talking about changing the SAMPLE RATE, just the NUMBER of SAMPLES in the file. SAy for example you have a wave file with 1 billion samples. Played back at a rate of 44,100 samples/sec yields 22675.73 seconds (bad example maybe, I don't know of too many 6+ hour movies, but you get my drift). Now say you resample and drop 1 million samples (1%) you get 990,000,000 samples. Play this back at 44,100 samples/sec (same rate as before, you'll note) and you get 22448.98 seconds. Voila. The wave is now shorter, AND the sample rate is still 44.1kHz, and is 100% specs compliant. There are fewer samples to play back, and thus the file is shorter when played at the same rate. The same applies to adding null samples to the wave. As long as you don't drop or add too many, the quality isn't noticibly degraded. This is _how_ programs like cool edit adjust length, but they also add sample interpolation as well (IMHO not necessary when we're only dealing with overall adjustments of a few percent).

I've made numerous PAL->NTSC SVCD's using this method with zero problems. Also check on besweet - it has a wave length adjustment routine built in using the method outlined above. (but was very buggy the last time I tried it.)
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Old 25th August 2003, 02:42   #12  |  Link
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WOW, Prosper.

I do stand corrected. I actually misunderstood your post. I'll try out BeSweet.

Regards.
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Old 25th August 2003, 16:26   #13  |  Link
nimrodim
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well if you change the sample rate and get the movie in sync you can actually Encode it at the desired wave length back to say mp3 when using graphedit and lame encoder.
This would not affect the sync....how this is done exactly i don't know...but i have used this method to change 44.1 to 48 KHZ.
I also don't know of a program which changes sample rate sound in a movie in order to sync it ( i would be happy to hear if there is anything like it - like aviinfo but for sample rate)
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Old 30th August 2003, 01:04   #14  |  Link
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Thanks nimrodim.

I, too, am in the waiting list for a program like AVInfo, but for sample rate.

Regards.
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