Re: (no subject)
Re: (no subject)
- Subject: Re: (no subject)
- From: Brad Ford <email@hidden>
- Date: Tue, 6 Dec 2005 12:06:09 -0800
On Dec 6, 2005, at 11:34 AM, Dan Morgan wrote:
I have read that apple lossless will give about a factor of two
compression,
but I was not seeing this when I used it. The audio being recorded
was the
sound of a conference room. I tried a variety of different
approaches in
my code and could not get it to compress, so I tried running WhackedTV
with output format set to apple lossless, and it also did not
compress.
Has anyone noticed this before?
Is apple lossless tuned to particular types of data and just does
not work
well on other types of data?
Apple Lossless typically gets 2:1 compression ratios, ***provided the
source is 16-bit***. It's highly optimized for 16 bit. I've seen it
do even better than 2:1 with recordings with a lot of silence. If
you feed the compressor larger integer samples, such as 20, 24, or 32-
bit, the compression efficiency goes down.
I just verified with WhackedTV that when I record from a 16-bit input
device (the built in microphone on my powerbook) to lossless, its
data rate is right around 50% of the data rate of uncompressed 16-
bit. I suspect you're recording from a 24-bit source.
-Brad Ford
QuickTime Engineering
Thanks,
Dan
P.S. Apologies if this has been discussed previously. I tried
searching the
archives but did not find this topic.
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| References: | |
| | >(no subject) (From: "Dan Morgan" <email@hidden>) |