[gst-devel] Re: [gst-cvs] thomasvs gst-plugins: gst-plugins/ gst-plugins/ext/lame/ gst-plugins/ext/mad/

Marc VanDaele Marc_VanDaele at Jabil.com
Tue Jun 15 00:02:06 CEST 2004


Some notes:
- There *is* a difference between mpeg-2 AAC and mpeg-4 AAC; don't know the
details though but IIRC, some is related to bit-alignment or byte-alignment
of audio-frames.
- Mpeg-4 audio can also be Celp (so mpegversion=4 does not imply AAC)
- Another difference between mpeg-1 and mpeg-2 audio is that mpeg-2 can be
multichannel (which almost nobody uses except for Philips on some
test/compliance DVD's).  If this is decoded by an mpeg-1 decoder, only the
BC (Backward compatible) part of it gets decoded, so you will get only 2
channels.  So, IMO, mpeg-2 audio *does* exist, although it is backward
compatible to mpeg-1

Hope this helps,


> -----Original Message-----
> From: Ronald Bultje [mailto:rbultje at ronald.bitfreak.net]
> Sent: Tuesday, June 15, 2004 12:50 AM
> To: Thomas Vander Stichele
> Cc: gstreamer-devel at lists.sourceforge.net
> Subject: Re: [gst-devel] Re: [gst-cvs] thomasvs gst-plugins:
> gst-plugins/ gst-plugins/ext/lame/ gst-plugins/ext/mad/
> Hi,
> [remove cvs from CC]
> You're using Fraunhofer's marketing methods as a starting 
> point, I used
> technical compliance and compatibility as a starting point 
> when coming up
> with those properties.
> If you really feel like this is important, I'll dig up some MPEG-2 AAC
> samples and see how different or similar they are to MPEG-4 AAC and
> MPEG-2.5 layer 3 and see in how far we should distinguish 
> between layer,
> version, aac-or-not and so on.
> If you then feel that our current method is wrong, then go ahead and
> propose something else. If you simply wish it to work in a 
> reasonable way
> (which is my only goal), then let's just stop here. We should 
> not waste
> time since we both have many better things to do.
> Ronald
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