[Buck_W]

I've got a 50 minute audio (aiff) file (speech) that I need to encode so that I can post it on my website. I've used both QuickTime Pro and Real Audio and this is what I've come up with so far:

QuickTime Pro MP4 encoded at 24bit ends up being an 18MB file.

RealAudio encoded for a 28k modem ends up being a 5MB file.

The kicker is, the Real Audio file is just as good in terms of quality as the QuickTime MP4.

I've heard that QT is far superior to RealAudio, so this puzzles me. It's obviously possible that I am missing something.

I've encoded the aiff file in QT at different bits in attempt to shrink the size of the file, but the sound quality suffers.

Does anyone have any suggestions that I should consider? Anything that I am missing? All input is needed and welcomed.

Thanks!

[Uncle Skeleton]

sorry, I'm not an audio person; what do you mean by 24bit? by your numbers it sounds like you didn't go down to the highest compression setting in QTPro (which is 8 kbits/second). When comparing different compression algorithms, you really should set them to the same bitrate and then compare quality

[Buck_W]

Originally posted by Uncle Skeleton:
sorry, I'm not an audio person; what do you mean by 24bit? by your numbers it sounds like you didn't go down to the highest compression setting in QTPro (which is 8 kbits/second). When comparing different compression algorithms, you really should set them to the same bitrate and then compare quality

Sorry for the confusion. I tried encoding the file at 8kbits and 12kbits. I selected "Recommended" on the output sample rate. The problem with encoding at the lower bitrates, is that quality suffers.

Is there anything I can try to lower the size of the file while maintaining a minimal level of audio quality (at least the same level of quality as the 5MB Real Audio file).

[Uncle Skeleton]

the only thing I know of is to lower the sample rate (you said you left it on recommended). Since your file is speech (not music), the recommended rate is probably overkill. I notice that the recommended rate for 16 kbps is 22khz, but 11 might be adequate (try it with a sample). There also seems to be an option for quality (versus speed I assume), put that on high (I don't really know, it just seems right. but you might want to experiment a little, or look for docs on apple.com). the RA stream is about 13 kbps, for reference. Oh yeah, I know if you encode to MOVIE with the mpeg-4 codec for video, you get higher quality than exporting to mp4. You can then export the mpeg-4 flavored mov file with passthrough to an mp4 file. I've long suspected that it's the same with audio, but never really experimented with super low-bitrate files.

edit: some more things to consider...Real does nothing but compression. it's not surprising that their compression would be at least slightly better. but there's also the issue of compatibility. any modern player will be able to play mp4, but only Real One will be able to play their codec. And it will have 50 minutes to download....

[esc]

The aac codec in QT 6 Pro (also called mp4) is optimized for music and is generally better than other codecs, at a given bitrate, when you get above 64kbps. It is very good at music at 128kbps and above.

It is not optimized for speech. When you get into the 24kbps and lower bitrates, it isn't surprising that other codecs would do a better job.

[Axo1ot1]

analogy: aac is good for music and movie soundtracks the4 way jpeg is for digital photos, real audio is better for speach like .GIF is good for text and simple graphics.

Either way. Don't ever use REAL audio under any circumstances. Why? Because its an enormous pain in the ass for most people to use. To date I have met nobody that prefers real to QT or WMP files. There are plenty of other codecs available in QT though, and I hear that the mpeg folks have a new audio codec that can get things to approximately %10 the size of an MP3 while preserving quality.

[Buck_W]

Originally posted by Axo1ot1:
There are plenty of other codecs available in QT though, and I hear that the mpeg folks have a new audio codec that can get things to approximately %10 the size of an MP3 while preserving quality.

Do you know what that new audio codec is? Any suggestions would be welcomed, thanks.