[mythtv] ffmpeg SWSCALE!

Steven Adeff adeffs.mythtv at gmail.com
Thu Aug 31 14:24:47 UTC 2006

On 8/31/06, Daniel Kristjansson <danielk at cuymedia.net> wrote:
> Resampling the audio correctly should be much cheaper, in coding
> and run-time, than resampling the video. Not because of theory,
> but because of how ffmpeg is implemented and because of how much
> less data you have to deal with. Problems with fixed block data
> like AC3/DTS can be overcome with a decode/encode step like in
> Mark Spieth's audio patch. For audiophiles decoding in the ffmpeg
> library and resampling (properly) in MythTV and NOT reencoding
> in AC3/DTS should avoid unneeded codec generation loss. We have
> at least one library in MythTV capable of resampling the audio
> properly, we simply don't use it in the NVP yet. Maybe in 0.23 :)

holy reading batman!

good stuff though, and I realize I really have very little
understanding of how video manipulation is done in the digital

As for the audio stuff. the problem with decoding AC3/DTS for
adjustments is how to get that information to a receiver digitaly.
SPDIF is the only format currently that allows for multichannel audio
transfer and it requires the data be in AC3/DTS. Until computers and
receivers support HDMI 1.3 with its ability to transfer ~10channels of
uncompressed high sample rate audio we're stuck with this. And theres
no way in hell I'm going to spend the money on an external sound card
with DAC's as good as the ones in my preamp, that alone would cost as
much as my current preamp and I'm saving up for an Anthem Statement

As I think about the tradeoffs in all this though, I would have to be
convinced that all the work will make a huge difference over the more
basic scaling and filtering when displayed on an actual 1080p display.
I also don't think the outcome of all this work will be worth the work
put into it over the type of processing ffdshow does. I could see this
type of processing being useful in conversion, but basic playback of
SDTV and DVD, I just don't see it being worth it.

Perhaps Daniel is on to something as a side project, a software
package for video processing. Of course I don't know what the software
that the "pro's" use does, it may take into account much of this

That said, please continue the thread on scaling, aslias, etc. if you
have any more good information its excellent reading for those of us

Hopefully all this talk will lead to some basic scaling and filtering
abilities. My apt-mate's 65" 1080p tv gets delivered in 2 weeks, and I
don't want to wait too long before proper scaling is implemented =D

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