question about converting to lossless
question about converting to lossless
- Subject: question about converting to lossless
- From: "Dan Morgan" <email@hidden>
- Date: Mon, 19 Dec 2005 17:33:09 -0500
Sorry to bother the list again, but I am still having trouble with
apple lossless compression. (Our client definitely ruled out any
lossy compression algorithms due to their perception that any
lossy compression other than chopping off bits or downsampling
might not stand as evidence in a court of law.)
I ran the following test. I generated a sine wave sampled at
16kHz-16bits. I created two quicktime movie files, one straight
LPCM data and the second compressed using apple lossless via
an audio unit format converter (and AudioUnitRender). I then
used the apple quicktime player to export the uncompressed movie
as apple lossless, hence producing a second lossless compressed
movie of the same data.
It turned out that both compressed movies reproduced the
sine wave perfectly. However, the one using the audio unit got
less than 20% compression, while the one using quicktime player
export got over 60% compression.
Why would these two ways of compressing using presumably
the same algorithm get such different amounts of compression?
Does it have to do with packetization/streaming versus working
with the whole file? Most importantly, how can I get the same
compression as the quicktime player export without having to
run the quicktime player manually?
Note that I have tried using AudioConverterFillComplexBuffer
and MovieExportToHandle but have not yet succeeded in
getting them working with apple lossless output.
Thanks,
Dan
_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today - it's FREE!
http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden