[MPlayer-dev-eng] [PATCH] [TEST AFILTER] Encode ac3 at runtime using lavc

[Ulion]

2007/11/20, Ulion <ulion2002 at gmail.com>:
> 2007/11/20, Ulion <ulion2002 at gmail.com>:
> > 2007/11/19, Ulion <ulion2002 at gmail.com>:
> > > 2007/11/19, Ulion <ulion2002 at gmail.com>:
> > > > Hello,
> > > >
> > > > As a wellknown feature of AC3Filter, it support encode ac3 at runtime
> > > > and passthrough it to spdif. With this feature, peoples has only a
> > > > decoder support ac3 can enjoy multi-channel audio from dts, aac, wma
> > > > pro, eac3, etc.
> > > >
> > > > Here's a test audio filter which do this work by using lavc to encode
> > > > ac3 at runtime. It works with me on ppc and intel, but seems it now
> > > > introduce a little more flick of subtitles on mac system.
> > > > And also, I'm not familar with audio filters, so the code probably do
> > > > things in some wrong way, or missed something, such as encode the last
> > > > audio frame, calculate the delay, etc, and also the calculate af->mul.
> > > > If this filter is worth to do, please give suggests on it, or someone
> > > > else make a better one.
> > > >
> > > > The patch need to reorder channels, so it rely on my reorder_copy
> > > > patch I sent just now. Or I should make it independent?
> > > >
> > >
> > > I forgot to say the usage:
> > >
> > > normally, add these to cmdline to encode multi-channel to spdif
> > > -channels 6 -af lavcac3enc=1
> > >
> > > full usage is
> > > -af lavcac3enc=A:B:C
> > >
> > > A: 0: output raw ac3 stream. 1: passthrough to spdif. current default is 0
> > > B: bitrate, if not set default for 2ch is 192kbits, and 384kbits for
> > > more than 2ch.
> > > C: min_channel_num to apply this filter, if nch is less than this
> > > value, detach the filter. current default is 5
> >
> > Slight update version.
> >
>
> I found the test filter introduce little gaps or tremolo, but I had no
> idea what caused it. Anyone familar with encoder or filter can help
> me?
>

The tremolo is some little noise like little spark, after some test, I
found the noise also exists when I use the current svn of ffmpeg to
encode some raw 5.1 wav, so this could caused by some encoder
bug of libavcodec

-- 
Ulion