mp3 player rates

mp3 player rates

by Timothy Takemoto -
Number of replies: 48

I am stil having a bit of difficulty with mp3 sound player raters.

I would like to record at CD 44KHz and export to mp3s with a bit rate of 40bs. But moodle's flash multimedia plug in plays the mp3 file at double speed. 

Michael Penney kindly advised that sampling rates of 22KHz work, and both he David Scotson kindly advised that I change the sample rate using Audacity.

When I halve the sampling rate to 22KHz then both Moodle and a standard MP3 player plays the file at half speed. This is harldly surprising. Halving the sampling rate, while keeping the same number of samples, will halve the speed.

However, when I halve the samping rate and then double the speed, the file plays at the correct speed on other MP3 players, but twice the speed on using the flash multimedia plug in.

Likewise if I double the speed and then half the sampling rater (reversing the order of operations) then the file still plays at teh correct speed on other Mp3 players but at double speed using the flash multimedia plug in.

And just for good measure, I tried halving the speed of the original file too, but that plays at half speed in both the flash mutlimedia player plugin and in other mp3 players.

Hmm...Perhaps I should try changing the speed of the mp3 file after export from audacity, using some other software. No. That did not work either. I doubled the speed of the reduced sample rate mp3 (column) 2 below using wavepad, so that it plays at the right speed in wave pad, but suddenly it plays at double speed in Moodles mp3.

It is very strange.

Please see the table below 


Sampling Rate/ Bit Rate / Speed

 Speed when playing using moodle multimedia filter

Speed when played using other MP3 players

1)

 44KHz / 40bs /normal

fast

 normal

2)

 22Khz /40bs /normal

slow

 slow

3)

22Khz /40bs /double

fast

 normal

4)

22Khz /40bs /double

fast

 normal

5)

44KHz / 40bs / half

slow

slow

6)

 

  22KHz / 40bs / double

fast

 normal


I don't know what other permutations I might try.

Any suggestions on what I might do?

Other players seems to be able to play the files at the right speed, and they are agreeing with each other. If you click the underlined file links in blue you can tests the files in other players. So this seems to be a bug in the flash player. Please can someone tell me who makes it so I can report it?

Cheers

Tim

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In reply to Timothy Takemoto

Re: mp3 player rates

by Timothy Takemoto -

Phew, I seem to have found an answer. If I export the original 44KHz

, then for reasons unfathomable, the mp3 plays at the right speed. I think that I will use them.

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In reply to Timothy Takemoto

Re: mp3 player rates

by David Scotson -

Changing the sample rate should not change the speed of the file playback unless the player is expecting a different sample rate from the one the file has.

This might happen because the player is hardcoded to only accept certain sample rates or because the file is contradicting itself by claiming to be a sample rate it is not.

Either way, something odd is going on.

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In reply to Timothy Takemoto

Re: mp3 player rates

by Sean S -
I'm trying to get audio to work and have looked at several threads on this forum but nothing seems to work for me. I keep getting the Alvin and the Chipmunks effect. does anyone have an ironclad solution that has worked for them.
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In reply to Sean S

Re: mp3 player rates

by Sean S -
problem solved.... I should have cleared cache... *embarrassed*
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In reply to Timothy Takemoto

Re: mp3 player rates

by Don McKenzie -
As a new user, I'm impressed beyond degree with most everything but puzzled on how to get some decent sounding audio as a resource Link. I've read all these post, but my audio does sound good and when I increase the size, it goes too fast. Is there some definitive answer on this audio problem? Thanks!
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In reply to Don McKenzie

Re: mp3 player rates

by Timothy Takemoto -

Hello Don McKenzie,
Sorry, I don't understand what you mean by "increase the size"? Perhaps you mean the sample rate?
In my experience, only some combinations of sample rates (when you record) and bit rates (when you export to mp3) work with the audio player that is built in to Moodle, due to the limitations of Macromedia Flash. You will find mention of the correct settings on the forums. The default audacity.org settings (at CD quality 44k i believe) work when you export to 32 or perhaps 40 bps mp3 files.
Timothy

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In reply to Timothy Takemoto

Re: mp3 player rates

by Don McKenzie -
Yes, I've read that - but the quality is less than desireable. I guess I'm surprised that this aspect of the program is somewhat a problem. Any idea of a work around to have better quality without the 'chipmunk effect'?
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In reply to Don McKenzie

Re: mp3 player rates

by Timothy Takemoto -

Dear Don MxKenzie,

Oops, I see now that we are on the same thread as the one where I was talking about the sample and bit rates. You don't like the quality above? I guess it is not ideal but I feel that it is adequate for listening comprehension, maybe. I am more scared of the load on our server than the sound quality.

I think that there is a higher bit rate that one can use with 44k sample rate that does not have the 'chipmonk effect' (I see that this is the term used in the trade). I am asking some about that sample rate now. He or I will get back to you.

Cheers,

Timothy

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In reply to Timothy Takemoto

Re: mp3 player rates

by Anke Tröder -

With voice recordings I use the following and have no probs at all and fairly small files; before exporting, I always use the Normalize Filter (from Effects), that will increase the quality considerably.

  • Quality Tab
    Sample rate: 44100 Hz
    Sample Format: 16-bit
    (set to fast-sync interpolation)
  • File format tab
    Uncompressed Export Format: 32-bit float
    Export Set up Bit Rate: 112

Anke

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In reply to Anke Tröder

Re: mp3 player rates

by Don McKenzie -

Anke,

What program are you using to format your audio: audacity? I downloaded it but I also use Goldwave to create audio. I'm willing to try anything to get the size and quality at the 'best'. Thanks!

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In reply to Anke Tröder

Re: mp3 player rates

by Don McKenzie -

Wow! Thank you very much... The audio - with the settings you mentioned - sounds great. Now, I'm going to experiment to see which of those settings actually eliminates the 'chipmunk' sound [as apparently we are now officially calling it - and for those searching the forum - it is the audio playing too fast].

I'll update this if I find something of interest or might be helpful to others - beginners like me. Thanks again!

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In reply to Anke Tröder

Re: mp3 player rates

by Josep M. Fontana -
Actually, Anke, I tried the settings you recommended and something very
strange happened: the quality is really good but I can only hear a few seconds of the recording.  This is with Firefox. With IExplorer it doesn't work at all. Of course, this might not have anything to do with the bitrate. Has anybody else experienced something similar?

Josep M.
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In reply to Timothy Takemoto

Re: mp3 player rates

by Stephen Henneberry -
I am asking some about that sample rate now. He or I will get back to you.

I guess that would be me...
I do not post a lot of audio files on my site, so I have not had to worry too much about file size at this point. The files are never streamed concurrently either, so the load on the server is not an issue for me. As such, I do not compress my audio files a great deal. Most of the files on my site are sampled at 44.1kHz and exported with a bit rate of 128. This gives me roughly a 1 MB/minute file size ratio.
I have used both Audacity and iTunes to export these files. I often just use iTunes, as it is my default CD ripper, and it just works. I have toyed with the bit rates, and I have yet to run into anything that sounds like Alvin and his pals. I have not documented my experiments as well as Timothy, but I haven't any problems yet.
As I plan to use more audio files in the coming semester, perhpas I will experiment a bit the the rates to see how iTunes fares...
Stay tuned...
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In reply to Stephen Henneberry

Re: mp3 player rates

by Stephen Henneberry -
I just ran a quick test with iTunes on my mac. I went into the preferance pane, selected importing and reduced the bit rate. The first time I selected 64, and a second time I chose 32 bits. I took the original file, which was 44.1kHz/128bits, and used the right-click convert option in iTunes to create a new copy of the file. When these were uploaded, both the 64 bit and 32 bit files played just fine in the flash player.

I just uploaded two more attempt at 24 and 40 bits, once again from the original 128 bit file. They worked just fine as well...
Maybe I will run the same series of conversions with Audacity tomorrow to see if I have the same results.
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In reply to Stephen Henneberry

Re: mp3 player rates

by Don McKenzie -
Are you playing these files with higher Hz and bit rates through the player built into Moodle? Are you using a separate window or playing within the same window? Or, do you you have some custom set up for your player? I can't get that quality to play correctly on the default player in Moodle. Thanks...
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In reply to Timothy Takemoto

Re: mp3 player rates

by Martin Dougiamas -
Picture of Core developers Picture of Documentation writers Picture of Moodle HQ Picture of Particularly helpful Moodlers Picture of Plugin developers Picture of Testers
You may be making this more complicated by double-guessing the MP3 player and the doubling/halving of speeds with wavepad.

As long as you use 44Khz, 22Khz or 11Khz then Macromedia Flash (which contains the MP3 routines that our player uses) will play your MP3 at the default speed. None of the other parameters matter.
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In reply to Martin Dougiamas

Re: mp3 player rates

by Timothy Takemoto -
Thanks Martin. I thought it was some combinations for sample and bit rates. That makes it a lot simpler.
Timothy
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In reply to Martin Dougiamas

Re: mp3 player rates

by Timothy Takemoto -

I thought that your answer above was going to the be answer to all my confusion - just export using 11, 22 or 44.

But I find that audacity does not seem to export using any of those bit rates three bit rates. Please see the screen capture below.  

And at the same time, I think that I have successfully created files for moodle using audacity.

So I am still somewhat confused.

Timothy

Attachment bitrates.jpg
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In reply to Timothy Takemoto

Re: mp3 player rates

by Timothy Takemoto -
I see that you were talkign about sampling rates, I presume, since you gave units of KHz not bit rates which are in bits per second. But all the same, it does not seem to be enough simply to record at a particular rate since there does seem to be a combination thing going on.

Anyway, after trying various speeds, it seems that 32bs works


I notice that I had worked that out before...rediscovering the wheel.

Tim
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In reply to Timothy Takemoto

Re: mp3 player rates

by James Phillips -
Timothy!

The 44.1Khz, 22Khz or 11Khz references refer to the sampling rates that have historically been used to sample analog files for digital recording (when CD's first became widespread most mastering was still analog, so an analog master would be digitally sampled for recording as a CD). The resulting digital sound file would then be recorded in multiples of eight bits per second (eight, sixteen, twenty-four, thirty-two) according to the number of outputs on the A/D and D/A converters used. As an MP3 file is already in digital form, there is no need for a sampling stage, so a rough idea of the quality can be given by the bits per second (the sound quality depends on many additional factors, such as cut-off frequencies of filters at the time of inputting the speech etc.). The scale shown above is simply the number of bits per second increasing in various multiples of eight. 32 bits per second should be more than adequate for speech in most cases.
Thanks for digging up the Georgian language bug by the way. I haven't had time to work on it yet but my hopes are high (as usual smile).
Cheers,
James Phillips
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In reply to James Phillips

Re: mp3 player rates

by Timothy Takemoto -
Dear James
Yes, I misunderstood Martin. But I misunderstood because it is not just a question of using 44.1Khz, 22Khz or 11Khz. Only some bit rates play at the right speed. I am not sure why or which ones, but some bit rates play like a chipmunk. Any ideas as to why?
Tim
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In reply to Timothy Takemoto

Re: mp3 player rates

by Martin Dougiamas -
Picture of Core developers Picture of Documentation writers Picture of Moodle HQ Picture of Particularly helpful Moodlers Picture of Plugin developers Picture of Testers
Here are some test files made with Adobe Audition... I picked the bit rates at random and they all seem to work. The only important thing is the sample rate.


Audacity is less than straightforward when it comes to this stuff. In fact I just tried it and it seems to be quietly dropping sample rates on the fly when low bitrates are chosen!! This must be your problem. Shoot for one of the combinations above and when you get a functional Audacity workflow, stick with it!
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In reply to Timothy Takemoto

Re: mp3 player rates

by James Phillips -
Timothy!
Are the one's that are playing at the right speed something along the lines of 16, 32, 64, 128, or are they just random? And did Martin use this as a sly opportunity to get some of his drumming played to wider audience approve ?

James
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In reply to James Phillips

Re: mp3 player rates

by Timothy Takemoto -

Martin, James,

Thanks for the drums. As you say, Martin, I will stick with a pattern I know works on Audacity.

I do tend to forget, when moving between computers. It would be nice if there is a pattern. I always use 44KHz as the sample rate, just in case I ever feel like burning a CD. Disk space is not a problem.

So here is a test

 okay
  super chipmunk
  okay
  chipmunk
  chipmunk
  okay
  okay
  okay
 okay

Can you see a pattern in that?

Timothy

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In reply to Timothy Takemoto

Re: mp3 player rates

by James Phillips -
Is this some sort of aliasing effect that disappears when the bit rate exceeds the sampling rate to some extent? I am not quite sure to be honest. I don't know enough about how the software is creating the sound files. There could also be some sort of approximation going on within the software that is more marked at lower bit rates (although I am not at all sure about this either). 
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In reply to James Phillips

Re: mp3 player rates

by Martin Dougiamas -
Picture of Core developers Picture of Documentation writers Picture of Moodle HQ Picture of Particularly helpful Moodlers Picture of Plugin developers Picture of Testers
It's simpler than that. Audacity is just silently changing the sample rate of the file automatically to suit low-bitrate sound. Normally this is not a problem because most software supports the full range of sample rates, but because Macromedia Flash only plays 44Khz, 22Khz and 11Khz then it doesn't always work.

Tim's examples above are actually using these sample rates (I determined this by downloading them and opening them up in an editor):

11Khz 16bs okay
16Khz 24bs super chipmunk
22Khz 32bs okay
32Khz 40bs chipmunk
32Khz 48bs chipmunk
44Khz 56bs okay
44Khz 64bs okay
44Khz 80bs okay
44Khz 128bs okay

So when using Audacity to export MP3 for use in Flash (and Moodle), you want to use bitrates where Audacity resamples sounds to 44Khz, 22Khz or 11Khz.
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In reply to Martin Dougiamas

Re: mp3 player rates

by Timothy Takemoto -
Devious, who'd have thought that Audacity would do something like that. I probably says in the instructions somewhere, but it does not tell you when you export.

Thank you for your music. Might your music be available for use in listening quizes, under CC's "noncommercial attribution"?

The original Rewd homepage is still available on 'wayback!' Wow... music, poetry, art, and boy-band photos; very interesting.
  
Timothy
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In reply to Martin Dougiamas

Re: mp3 player rates

by Timothy Takemoto -
BTW this article
http://www.sonify.org/home/feature/remixology/004_prepareloops/page2.html
describes all the posssible sample rate and bit rate combinations for Flash and whether they support mono or stereo. The article is about getting flash to do the commpression, but I think that the sample rates and bit rates that flash can compress to may also be the ones that it supports.
Timothy
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In reply to Timothy Takemoto

Re: mp3 player rates: The curse of the chipmunk returns

by Timothy Takemoto -

The curse of the chipmunks return.

I have a large file recorded at 44khz. This *should* be okay if I could export to mp3 keeping this sampling rate.

Also, even using Audacity, it should not produce chipmunk audio at 16pbs and 32bps bearing in mind that, as Martin Dougiamas kindly pointed out in his table above, Audacity reduces the sampling rate to 11KHz and 22KHz when exporting to 16bps and 24bps respectively.

However, exporting to mp3 at 16, 24, and 32 bps all seems to produce chipmunks.




and any higher bits per second than that produces a file that is too large. I guess that Audacity is dropping sample rate, as noted above, but in a random way perhaps.

Also, I do not seem to be able to change sampling rate using Audacity, or at least, when I do that in Audacity, the speed of the file slows proportionate to that change so that the file plays e.g. setting the sample rate to 22Khz (from 44Khz) like this,  
changing the sample rate using audacity
the file now plays twice as slowly in Audacity. Ignoring this fact and exporting the slow file to mp3 results in



which is still chipmunking (athough it is not far off at "22Khz at 32bps").

Is it time to invest in an audio editor that
1) Exports at the sampling rate that it says it is exporting at
2) Can change sampling rate without changing the speed of the audio
This is a shame. So many of us are using open source Audacity.

In the meantime, as a workaround, it is possible to prevent Moodle from linking resources to the flash player by
1) Turning off this feature globally in the Admin filters settings
2) Using a web page and use the <nolink> tag (i guess)
3) Link as a resource in the same window and check "Put resource in a frame to keep site navigation visible" -- this means that a non flash (non-moodle, in my case windows media player) media player will be used.

The latter is the workaround that I am using now.

Tim

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In reply to Timothy Takemoto

Re: mp3 player rates: The curse of the chipmunk returns

by Timothy Takemoto -

It seems that Goldwave ($45) has mp3 export which does not drop sampling rates, and does what it says it will do. This is 44KHz at 32bps



No chipmunks on Goldwave.

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In reply to Timothy Takemoto

Re: mp3 player rates: The curse of the chipmunk returns

by A. T. Wyatt -
I like Goldwave. I have used it for many years and think it is a reasonably priced and good piece of software.

atw
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In reply to A. T. Wyatt

DVD editor

by Ray Lawrence -
Not wishng to hi-jack this discussion, but does anyone have a recommendation for a good editing tool for .mpg files? This is a one off job (recorded off the TV and forgot to stop recording, resulting file too big to burn to a DVD) so I don't really want to buy a special program which I'm unlikely to use again or much.

Cheers
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In reply to James Phillips

Re: mp3 player rates

by Martin Dougiamas -
Picture of Core developers Picture of Documentation writers Picture of Moodle HQ Picture of Particularly helpful Moodlers Picture of Plugin developers Picture of Testers
No, that's not me playing in the sample smile, it's Radiohead and "Knives out".

But here's some samples of my band from
and

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In reply to Martin Dougiamas

Re: mp3 player rates

by James Phillips -
Martin!
What is the name of your band? With that snippet of information, I can trawl the Internet for pictures of you in your heyday, and stick them on parts of this site just when you are least expecting them wink .

James Phillips
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In reply to Timothy Takemoto

Re: mp3 player rates

by Chick Beckley -
This is a great thread and I'm certainly not an expert in this, but I use Quicktime to do all of my MP3, MPEG4, WAV, AIFF and all other sound conversions and bit rate conversions with no problems. It is easy and a wonderful tool.

I also use Sorensen Squeeze - another great digital video and audio conversion tool.

Chick Beckley
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In reply to Chick Beckley

Re: mp3 player rates

by Steven Day -
Chick,

Would that be Quicktime Pro, by chance? With QT 7, I don't see many options available for sound conversions.

Thanks in advance.

Steven
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In reply to Steven Day

Re: mp3 player rates

by Zev Steen -
It seems to me that the flash player embedded in Moodle is a little quirky.  I got around it by just adding a resource web page and created a link on that page to the audio file.  This gets around the built-in flash player and opens the file in the users native audio program (Quicktime, Windows Media, RealAudio, etc.).
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In reply to Zev Steen

Re: mp3 player rates

by Joseph Rézeau -
Picture of Core developers Picture of Particularly helpful Moodlers Picture of Plugin developers Picture of Testers Picture of Translators
What do you mean exactly by "a little quirky" ?
Joseph
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In reply to Joseph Rézeau

Re: mp3 player rates

by Zev Steen -
"little quirky" - based on all the posts above, it seems there is no consistant way to solve the problem of the chipmunk effect in the built in moodle flash player.  That is why I suggested getting around it instead of solving it.
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In reply to Zev Steen

Re: mp3 player rates

by Tony Hursh -
It's not a problem with the Moodle Flash player per se. It's a problem with Flash.

And, yes, there is a consistent way to get around the problem. If you record your file at one of the rates that Flash supports, it will work fine. If you don't, it won't.

smile

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In reply to Tony Hursh

Re: mp3 player rates

by Eric Hagley -
I'm not so sure. If I upload an mp3 file to my server and link to it the mp3 plays fine within the course. Upload the same file into the course files and link to it there and I get chipmunks (this is when I'm making a quiz, when I use the "link to a file or website" from the add a resource menu the file plays fine - different player though). This is with 1.6. Never seemed to have the problem before. 
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In reply to Eric Hagley

Re: mp3 player rates

by Joseph Rézeau -
Picture of Core developers Picture of Particularly helpful Moodlers Picture of Plugin developers Picture of Testers Picture of Translators

Sorry to say so, Eric, but your post is rather confused (and confusing). mixed

Could you state clearly the different steps you take to get an MP3 file a) to play correctly and b) to play with the chipmunks effect. Could also specify the sampling rate that you use for your MP3 files. Finally, could you say whether the Moodle MP3 Flash player is being displayed or not in either case.

Thanks,

Joseph

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In reply to Joseph Rézeau

Re: mp3 player rates

by Eric Hagley -
Sorry! Poor excuse, but it was late when I posted.
Ok, I made an mp3 file using audacity on my mac. I used 44100hz (as well as 22050 and 11025), default sample format 24 bit, high sinc interpolation, export mp3 setup bit rate of 56. (and another example with the above sample rates but a set up bit rate of 128). I uploaded the files to my moodle site using the standard method so that they appeared in the files section and I could link to them from there.
I also uploaded them to a subdomain of my site using cpanel's file manager.
When I linked to them in the files section of the moodle site, I got the chipmunks.
When I linked to them using the address in the sub domain they were fine.
(the flash player was being displayed normally)

When I created a "link to file or web site" resource and linked to the mp3 in the file section of the moodle site I could hear that fine - but it doesn't show the standard flash player, rather it shows the browser's player.

Now, tonight I redid this process just to make sure that I was right - only thing that happened was they now all worked!

I don't know what the problem was last night - cache??? Tired??? Chipmunks on the roof??? I'm not sure.
It has been a frustrating couple of days! But as it seems to be working now, I'm fine.
Thank you, though, for taking the time to look at the post!
Kind regards,
Eric
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