[Newlug] Linux Meetup Tonight
gaveup at gmx.net
Tue Jun 12 18:50:54 CDT 2007
Just a correction. It wasn't an AAC encoder or for MPEG-4. It was a
patcher, using custom parsing routines, for parsing and patching VBR AC3
audio to CBR AC3. FWIW, this solution does, technically, violate the
AC3 specs, but having tested it on a variety of equipment from highend
receivers to the various software decoders it has not failed once.
For those that were at the meeting and might be interested in a bit more
background. The issue was VBR AC3 muxed in an avi wasn't playing
properly and would stutter video and go out of sync when there was a
bitrate change. This solution patches the audio to the highest bitrate
in the stream, without reencoding thus not losing any quality. It
should be noted that this method was not the best of the 2 solutions for
to the issue. The better solution was to fix an avi muxer (all I've
seen suffer this problem) to correctly handle VBR AC3. The reason that
this method was not chosen is because it required more research in an
area I was, and still am, unfamiliar with and the need for a fix was
becoming more dire (anyone who has dealt with HDTV knows how much space
it can chew up.) For more information on the issues with handling AC3
(and VBR MP3) in an avi container you can search virtualdub.org. There
is an essay from several years ago discussing the issues, the 'hack'
that makes it possible, and some of the details behind why the hack
Also, if anyone is interested in the code it can be found at
http://ac3c.vidphiles.com. A dicussion thread of the software can be
found at http://forum.doom9.org/showthread.php?t=92325. In addition, in
the development section of the doom9 forums there are a few threads that
predate the software where brainstorming and discussion took place about
a possible fix for the problem. As mentioned at the meeting for anyone
looking at the code it is pretty ugly proof of concept code that I never
had a chance to go back and redesign/rework (it's still on the todo
list). As such, a lot of the features are buggy or just don't work
(audio delaying/cutting based on vcf/cutting based on video frame
numbers.) Some of the bugs were fixed, but due to a HD loss the source
code was lost and as such those changes were never released to the
public. Besides, the core feature worked, and there are other apps to
handle the other tasks.
I realize this isn't really linux related. I'm not even sure the code
will compile on linux without changes, but people seemed interested in
it at the meeting so I thought I'd post a bit more detailed info.
gaveup at gmx.net
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On Tue, 12 Jun 2007, Ryan D. Hatch wrote:
> Morning, Don...
> You could have spoken with Josh last night. He is brilliant with HDTV.
> He's written a low-level AAC encoder for MPEG-4. We talked about the best
> video capture cards for HDTV in Linux (using Myth, etc.).
> Just don't screw up. If your wife misses her Grey's Anatomy - you just
> might lose one of those One-Night-Out-Per-Week tokens. [wink] Next time
> you can carpool with Mike, who is also drove from Manitowoc.
> It was a good time. Try to get pictures up soon.
> -----Original Message-----
> From: newlug-bounces at newlug.org [mailto:newlug-bounces at newlug.org] On Behalf
> Of Don Seiler
> Sent: Tuesday, June 12, 2007 8:06 AM
> To: newlug at newlug.org
> Subject: Re: [Newlug] Linux Meetup Tonight
> Sorry I missed it. I'm definitely interested in MythTV now that I
> can't get some content off of my DISH Network DVR. ><
> On 6/12/07, telecomtom at vedatel.com <telecomtom at vedatel.com> wrote:
> > ryan hatch wrote:
> > > NEW LUG Meets in De Pere.
> > > When:
> > > Monday, June 11th
> > > 6:30pm - 8:00pm
> > > Where:
> > > Sports Corner Bar & Grill - Upstairs
> > > 500 Grant Street
> > > De Pere, WI 54115
> > a great meeting. many thanks to Sports Corner Bar & Grill for hosting the
> > meeting. for those of you who didn't have the opportunity to be there,
> > here are some of the topics we discussed:
> > * next meeting will be second monday of july (the 9th), same time, same
> > * more meetings! locations, regular meeting time, possibility of having a
> > week night and a weekend meeting. what's important at this point in time
> > is that we continue to meet, build the momentum and group identity.
> > * put your individual profile, pictures, linux interests, etc. on the
> > newlug wiki. or remain anonymous. whatever you feel comfortable with.
> > * ryan will be talking to the host IS/IT contractor about details for wifi
> > router and internet access.
> > * pchdtv, mythtv, antennas, stations, and things like that.
> > * open-source software from sun: openjdk (java). also opensolaris -- just
> > in case the linux kernel gets munged in court by the friendly folk at
> > microsoft.
> > * outreach to universities, tech colleges, high schools, to bring more
> > participants in the lug.
> > * linux game day
> > * possible presentation topics for future meetings. anyone want to
> > I know we talked about a dozen or so other items, but this is all i can
> > remember on a caffeine-less brain.
> > -- TT
> Don Seiler
> oracle blog: http://ora.seiler.us
> ultimate: http://www.mufc.us
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