>if I want to convert some aiff files to mp3 to be downloaded from net…
> what specs should I aim at to keep size down but quality ok…

These are the settings I use for good quality speech in itunes:

Stereo Bit rate: 80kbbps

Sample rate: 22.050kHz

Channels: Mono

NOTE: This results in a 40kbps file (the mono file ends up at half the stereo bitrate)
A 20 minute talk will be about 6Mb and sound good.

If I am ripping from CD for speech for my ipod, say a story, and size is not so important, I set itunes to:

96kbps,
44.1kHz,
mono.

Which gives an output of 48kbps.The place you put these preferences in is itunes:preferences and click on the advanced icon then importing tab then Setting:Custom you can set the various options according to what you want.

Click here to read how to make the filesize (and quality) lower using LAME.

1. SMALLEST FILE SIZE ACCEPTABLE QUALITY.
For very small file size (4MB for 20 minutes) and acceptable quality,
use the LAME encoder (the the separate article on Itunes songs to find out about the LAME encoder) with the following arguments in the ‘Encoding options’ Box:

-V 9 –vbr-new -mm -h -q 0

2. An even better option than above but slightly more complicated is:
Firstly convert the file to 22khz sample rate and mono, (eg in Audacity)
then use the following LAME settings:

-V 8 –vbr-new -h -q 0

3. BETTER QUALITY AND ACCEPTABLE FILE SIZE.
For about twice the size files (8MB for 20 minutes of speech) but very very good quality try this in LAME encoder:

–preset voice

OR

-V 8 –vbr-new -h -q 0

4. BEST QUALITY. Use itunes. Although LAME is better for music, and lower bitrate spoken word, itunes is great for 40kbps spoken word and above. CLick here to read about the best settings on importing spoken word into itunes here.

A podcast is simply a small file called an ‘RSS feed’ that points to the audio (mp3) file that you want to podcast. This little ‘RSS feed’ file is then registered with a podcast site, like the apple itunes podcast site.

How it works
When someone clicks on the podcast icon in itunes, it takes them to the apple itunes podcast site, where they can search for the podcast they want. The apple site then points their itunes software to the little RSS file, which then points their itunes to the mp3 file that contains the audio. It sounds complicated, but it’s really just a series of little signposts that eventually point to the mp3 file.

So as you can see, we need to put the mp3 file up, then create an RSS feed that points to the mp3 file, and then we register this RSS feed with itunes. We can then access the podcast from itunes.

So really the audio file alone is not the podcast, the rss file is not the podcast, the itunes store is not the podcast. The podcast is really the whole set of signposts.
The advantage of a podcast is that all the audio files are easy to find because they are centralised into the itunes store, and the process of downloading them once you are subscribed is automatic.

Let’s look at how to do it step by step.

1. Put up the mp3 file

The first set is to make an mp3 file (eg via ‘itunes’) and then place it on the internet somewhere using an ftp program (‘cyberduck’ is a good ftp program). You will need an account on a webserver to do this. This is dealt with elsewhere on ‘How to put a file on the internet’). The file will be called something like ‘talk1.mp3′ and it will be at a location somethign like ‘http://mywebsite.com.au/talks/talk1.mp3′. For our example we used the real file called ’20060212.mp3′ which we put on the web at at http://sermons.dpc.org.au/1john/20060212.mp3

2. Make an RSS file that points to the mp3 file

Now we need to make an RSS file that will point the the mp3 file to tell the podcast directory (in this case, the apple itunes podcast directory) where to find the mp3 file. There are hundreds of programs to make an RSS feed (eg ‘feedforall’) , but it’s hard finding a free one! Vodcaster looks good but it’s only for tiger. One good free one is at http://www.phelios.net/rss-writer.html it’s easy to use. The program will ask for information like the name of the mp3 file, artist, title of webcast etc, and it will put all this information into a file called an RSS file, which it will save to your hard drive. The program will give the file an extension of .xml So we called ours dpc and it was saved as ‘dpc.xml’

3. Put the RSS file somewhere on the web

It doesn’t matter where. We uploaded ours to http://sermons.dpc.org.au/dpc.xml

4. Register the podcast with itunes

The last step is to let itunes know where the rss file is kept. Open up itunes, and click on the ‘podcasts’ icon. Down the bottom click on ‘podcasts directory’. This will take you to apple’s podcast page on the itunes music store. There is a link called ‘Submit a Podcast’ which you can click on. It will ask you for the podcast feed url. This is the address of the rss fiel you just created. (Eg http://sermons.dpc.org.au/dpc.xml) Paste the address and click continue. Unfortunately you need to then enter your apple ID, you’ll need to register with apple to get one, it doesn’t cost anything, it’s not a .mac membership, just an apple id. Apple will send an email telling you when the podcast has been approved. It may take an hour or two.

5. Subscribe to the podcast

You should now be able to find your podcast on the ituens webpage. Go to itunes, podcasts, podcasts directory. There is a box to search for a podcast. Type in part of the name of your podcast (eg I might type in ‘Dubbo’) and click ‘search all podcasts’. It will display all the matches, in our case, 1 match – ‘DPC BibleTalks’. Click on subscribe to subscribe ot the podcast. You are now subscribed to the podcast!

6. Link to the podcast

Now the final step is to link to your new podcast from a webpage. Open itunes podcasts and next to your subscibed podcast title is a little right arrow. Click on this and it wil take you to the itunes homepage for your podcast.

If you right click on the podcast entry down the bottom, there is an option called ‘Copy itunes Music Store URL’. Click this and then it will copy the URL to the clipboard. You can then paste this into your homepage or email it to your friends. Ours was http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=121967957&s=143460&i=2214949

If you click on this it will open itunes and take you to our newly created podcast!

1. Record the speech using audacity. (Don’t use an mp3 player unless it records in aiff or you will lose quality when you re-compress to a lower bitrate mp3)
2. In Audacity, edit the bits out that you don’t want (like blank bits at the start or end of the recording)
3. In Audacity, I like to add some compression (this makes the louder sections quieter and the quieter sections louder to make the listening level more constant within the track and also normalise (this amplifies the whole track to the loudest it can be without being so loud it distorts. You should compress first (as this reduces the highest levels, then normalise. The following settings are a good start:
   Compression
   threshold -12dB
   ratio 2:1
   attack 0.2 secsNormalisation
   Normalise using default. (centre on 0 and normalise to -3db)
4. Next you need to edit the ID tags, which contain the information that is displayed in itunes. For our sermons at Church we do it like this:
   Song title = passage, (“1 Thess 1″)
   Artisit = preacher, (“Bryson Smith”)
   album = DPC (“DPC”)
   genre = speech
5. Finally, export. Firstly I would save as an Audacity file to keep, or as an AIFF, so you have a full quality version on hand, then export to mp3 for the internet.
   It’s a toss up between file size and quality. Anything below 40kbps, you start to notice ‘ringing’ (called aliasing) around the high frequencies. We used to record our sermons at 32kbps, but this has enough compression noise to be annoying. 40kbps is tolerable, just noticeable. You don’t need stereo for speech, so mono is fine. If you set itunes to 80kbps, mono, it will output a 40kbs file. I like to export from audacity to aiff, then compress with the itunes encoder. I don’t remember why I do this, perhaps the audacity mp3 encoder is lower quality at lower bitrates than the itunes one.

That’s it! Check the quality, upload it to your webpage, or download to your mp3. If you are just taking a file from the web, and just want to make it smaller for you ipod, you can skip all the audacity bits and just encode it with itunes at the lower bitrate.