Subject: [linux-audio-user] format conversion question (long)
From: ben-extra_AT_MIT.EDU
Date: Wed Jan 08 2003 - 02:37:39 EET
Hi,
I have a few questions about audio format conversion. After reading a
description of the purpose of this list, and reading the list itself for
about 10 days, I think this is an acceptable place to be asking. If, in
fact, my questions are best asked someplace else, please let me know,
and my apologies.
I have quite a few recordings that were made from a RealPlayer 8 live
stream. As saved by vsound (.au format), they are about 500 Megabytes
each! Seeing as RealPlayer reports the (original) stream/broadcast as
12.4 Kbps, and the recordings are about 3.5 hours long, I am quite sure
they are being saved to disk with much higher quality then needed. :-)
My basic need is to reduce their size. I am not an expert in audio
processing, and I would prefer not to become an expert in order to make
the correct choices for this conversion. Hence, I hope that this is an
easy question for somebody(s) reading this list to answer. I don't need
to conserve every possible megabyte of disk space, indeed I would prefer
to be conservative, and not lose any quality. The recording is of low
AM radio quality as it is...
I have sox installed on my system, so I am trying to use that. I read
through the man page. I don't feel a need to have stereo, so I took a
wild guess as to what rate would be appropriate and did the following.
My attempt was to produce a mono recording at 8000 samples per second.
marit_AT_chipmunk:/var/tmp$ sox -V test.au -c 1 -r 8000 test.wav polyphase
sox: Detected file format type: au
sox: Found Sun/NeXT magic word
sox: Input file test.au: using sample rate 11025
size shorts, encoding signed (2's complement), 2 channels
sox: Input file test.au: comment "test.au"
sox: Writing Wave file: Microsoft PCM format, 1 channel, 8000 samp/sec
sox: 16000 byte/sec, 2 block align, 16 bits/samp
sox: Output file test.wav: using sample rate 8000
size shorts, encoding signed (2's complement), 1 channel
sox: Output file: comment "test.au"
*******
The resulting file sizes are then:
-r--r--r-- 1 marit marit 527881224 Jan 6 15:43 test.au
-rw-r--r-- 1 marit marit 191521568 Jan 7 19:13 test.wav
I am open to any suggestions. I wasn't expecting 3.5 hours of
low-quality audio to be 200 MB, but maybe I am naive. Am I using the
wrong tool? As a separate question: How much space would I save using
mp3 or ogg encoding?
Thanks in advance,
Ben Blout
This archive was generated by hypermail 2b28 : Wed Jan 08 2003 - 02:40:21 EET