[linux-dvb] Re: Speed of DVB audio decoding

[Niklas Peinecke <peinecke@gdv.uni-hannover.de>]

Hi Radovan,

thanks for your report, this conforms mostly with my own experiences.
Nevertheless watching TV under Windows is not acceptable for me: Audio 
is broken most of the time and I have a 400Mhz CPU! I think this may 
also have something to do with audio hardware, currently I use a SB16 
(ISA bus), maybe a pci card would do better.
I'll try a pci card next and then give xine a try.

Thanks,

Niklas

Radovan Garabik wrote:
> This is just a description of what I found out, maybe to help
> others with similar problems...
> My setup is PII 266 MHZ with Skystar2 (2.6B), which is about as
> slow as you can get (but at least it has a good video card :-))
>
> Watching TV under Windows is aceptable, channels with better resolutions
> (such as Canale 5, Italia 1, german channels on Hotbird) are jerky,
> but watchable (but switching channels takes forever).
>
> First I tried to use mplayer, while low resolution channels were OK,
> high resolutions were unwatchable. While experimenting with different
> video and audio codecs, I accidentally found out that leaving sound out
> makes the picture quite smooth. So I took a piece of audio and tried 
> various mp2 players:
> mplayer (with no video) eats about 15% CPU
> mpg321 also 15%
> madplay 10%
> mpg123 (the nonfree one) about 6%, with downmixing to mono and
>    downsampling even much less (2-3%)
> so I went the difficult path of upgrading the system to install 
> latext xine, and to my surpsise, picture was quite acceptable (maybe
> a little bit worse then under Windows, but channel switching is fast)
>
> IMHO xine uses libmad for audio decoding, and that 4% of CPU time seems
> to make the needed difference.
> I have yet to compile mplayer with libmad (it takes a while!) to 
> see how it performs, but it is a pity mpg123 is nonfree - it
> has been written a long time ago, when speed of decoding was very
> important (I remember playing mp3's on 66 MHz 486 :-)), and nowadays
> no-one bothers with such kind of optimalizations.



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