Can't get the same samples using speed change

bomber1978 · Post by **bomber1978** » Mon Apr 16, 2012 11:39 am

Hello,
I'm using Windows 7 Pro 64bit and Audacity 2 (19.8MB), I have previously been using an Audacity version from around 2009/2010.
I have a raw .wav file I did some speed changes on back in 2010, when making the same speed change to the same raw file with this new Audacity and comparing in EAC .wav compare it's making different samples...
Can anyone please give some ideas what it might be???
I am certain I'm using the same raw file, and am certain all I simply did was make a speed change and save as.wav, I am sure it has to be something do to with Audacity...
In fact the same folder I have a file I did not speed change, and the samples match with the same file I just saved back off a disc, so I am pretty much 100% sure the different samples when speed changing is something to do with Audacity.
Bye the way, I have set the following "High Quality" dither to "None" in the Quality Preferences", but it still does not match the samples to the old Audacity I was using (however it did fix a problem of this current Audacity making different samples every time the same speed change is made to the same file), but I would like to know why it's still making different samples to a previous version?
Thanks

Post by **steve** » Mon Apr 16, 2012 1:18 pm

What is the format of the RAW data?

bomber1978 · Post by **bomber1978** » Mon Apr 16, 2012 1:19 pm

steve wrote:What is the format of the RAW data?

.wav

Post by **steve** » Mon Apr 16, 2012 1:25 pm

I presume that you mean it is PCM?
How many bits per sample? 8, 16, 24, 32, 64?
Signed integer? Unsigned integer? Floating point?
What's the sample rate?
How many audio channels?

bomber1978 · Post by **bomber1978** » Mon Apr 16, 2012 1:28 pm

steve wrote:I presume that you mean it is PCM?
How many bits per sample? 8, 16, 24, 32, 64?
Signed integer? Unsigned integer? Floating point?
What's the sample rate?
How many audio channels?

PCM 16bit 44.1KHz 2ch stereo

bomber1978 · Post by **bomber1978** » Mon Apr 16, 2012 1:44 pm

I can't figure it out....
I have a disc with the raw unedited files, and a disc with the speed changed files...
The disc with the speed changed files has 1 file which has not been speed changed, and the samples of that match with the samples on the disc with the raw data....
So that tells me it has to be something to do with the older and newer version of Audacity when making the speed change....

Post by **steve** » Mon Apr 16, 2012 1:54 pm

Have I got this right:
You have two RAW files - one is the original and one has had the speed changed.
If you now change the speed of the original file, the result is different from the one that you made two years ago?

How much different is it? Does it sound different?
How can you be sure that you are using exactly the same settings as you used in 2010?

bomber1978 · Post by **bomber1978** » Mon Apr 16, 2012 2:02 pm

steve wrote:Have I got this right:
You have two RAW files - one is the original and one has had the speed changed.
If you now change the speed of the original file, the result is different from the one that you made two years ago?

How much different is it? Does it sound different?
How can you be sure that you are using exactly the same settings as you used in 2010?

Yes you are correct, I'm not sure I can hear a difference but I have noticed the difference by comparing with the EAC programme in "WAV Compare" and it says the samples are different...
I presumed the default setting for the different Audacity versions would be pretty much the same?, I have never changed any setting on either..., shouldn't the samples be the same?

PGA · Post by **PGA** » Mon Apr 16, 2012 2:04 pm

bomber1978 wrote:So that tells me it has to be something to do with the older and newer version of Audacity when making the speed change....

Why do you expect two different versions of Audacity to produce "bit identical" results? Those two versions may (will?) each have been built using different versions of the code libraries of the various tools. Software is constantly being updated. Why do you assume that the Change Speed code hasn't been changed over the two year period?

bomber1978 · Post by **bomber1978** » Mon Apr 16, 2012 2:10 pm

PGA wrote:
bomber1978 wrote:So that tells me it has to be something to do with the older and newer version of Audacity when making the speed change....
Why do you expect two different versions of Audacity to produce "bit identical" results? Those two versions may (will?) each have been built using different versions of the code libraries of the various tools. Software is constantly being updated. Why do you assume that the Change Speed code hasn't been changed over the two year period?

I don't know about it in that much detail, I just expected the same speed change would produce the same samples (for example if right now I changed the raw file by the same speed change twice both output files will have the same samples).
OK so I take it then it's not actually a problem.........

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Can't get the same samples using speed change

Can't get the same samples using speed change

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