[mythtv-users] Preserving HDTV AC3 audio stream whilst transcoding

[Tom E. Craddock, Jr.]

Joe Barnhart wrote:

>--- Isaac Richards <ijr at po.cwru.edu> wrote:
>
>  
>
>>Current CVS myth, a gf4 (4200), 66.26 drivers, not
>>using XvMC (slower than Xv 
>>without a better card), no deinterlacing/filtering,
>>doesn't matter what 
>>display res.  'Extra audio buffering' is turned on.
>>
>>720p plays perfectly on this machine.
>>
>>Of course, none of that is with the OSD displaying
>>anything during playback - 
>>I don't have enough cpu to blend in software. =)
>>    
>>
>
>I'm puzzled by the statement that the cpu usage
>"doesn't matter what display res."
>
>A simple calculation shows that a stream played at
>1080i with 24-bit color pushes about 1.5Gbps through
>the video card (1920x1080 x30fps x24bpp).  A 720p
>stream pushes about 1.3Gbps.  If your output device is
>720x480i, you're looking at about 250Mbps.  I would
>think the difference in these OUTPUT resolutions would
>have a profound effect on system performance.
>
>I have had severe difficulty playing 720p or 1080i
>source on my 1080i output device with an Athlon 2800. 
>The player built into Myth just couldn't keep up with
>it, regardless of extra audio buffering or any other
>setting.  This was while using Xv.  If I changed to
>XvMC I could play the stream, but it would hang if I
>tried to jump forward or backward, or whenever the OSD
>tried to fade off screen.  It was just not usable with
>XvMC.
>
>Because I obviously needed more horsepower to use Xv
>at 1080i output, I bought a P4 3200 machine and I'm
>now able to play HD sreams smoothly.  All of my
>experiments are with plain 0.16 MythTv under
>KnoppMyth.
>
>I don't have any comparisons with Xine or Mplayer, but
>I can say for sure that the player built into Myth is
>not able to keep up with 1080i while playing on an
>Athlon 2800 or slower, using Xv and a nVidia 5200 (8x
>AGP).
>
>I'm interested in trying some of the later work done
>by Doug and others.  I'll be able to try CVS at some
>point, and then I can begin to try the patches.
>
>
>		
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>  
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I can say that I can watch LiveTV or recorded programs from my 
pcHDTV3000 on my machine, which is a AMD Athlon XP2000+, 768 RAM, FX 
5700LE (Nvidia Driver 6629) w/XvMC , a bit of flickering with the OSD on 
the display, but once its gone, very smooth, can skip commercials, can 
pause, rr, ff, change channels, running MythTV from CVS 4 days ago.

Tom Craddock, Jr.