[mythtv-users] Prebuffering pause on Frontend playing back BBC HD
andrew.lyon at gmail.com
Tue Jan 2 12:15:30 UTC 2007
On 1/1/07, Chris Dos <chris at chrisdos.com> wrote:
> Mike Choy wrote:
> > I've just built a amd 4200 X2 with 1GIG on asrock motherboard using suse
> > 10.2 and packman rpms. The asrock has an on board Nvidia gforce 6100
> > GPU, but uses shared memory. On playing BBC HD in the UK (h.264 based
> > stream) I'm getting stutter and NVP prebuffering pause on running
> > mythfrontend. Have tried all permutations of XV, standard mpeg decoders
> > , deinterlacing etc
> > I was under the impression also that playback should not be a problem.
> I think that this shouldn't be a problem for mpeg2 playback. But from what I
> understand, the decoders for h.264 in ffmpeg aren't quite up to snuff for speed.
> So your system might not be powerful to playback h.264. Can you play back
> mpeg2 without prebuffering pauses?
> > I have recorded the stream and on playback it still stutters. Top shows
> > 50.1% CPU utilization.
> You might want to hit the "1" key during top to show each individual core's
> usage. It's probably one thread that is maxing out one of the cores.
> > As this is a brand new rig here is what I'm doing to try and trouble
> > shoot this. (any further hints and data points also welcome)
> Yea, I'm kinda in the same boat as you are. Are you using SVN? I don't know if
> the packman rpms are MythTV RPMS or not. I'm running stock 2.6.19 kernel that I
> rolled from from kernel.org, Debian Sid, MythTV SVN, and the latest nvidia driver.
> > 1. Have downloaded 720p and 1080p h.261 sample movies from digital
> > digest (pirates of the Caribbean)
> > http://www.digital-digest.com/movies/pirates_of_the_caribbean2_h264_1080p_trailer.html
> > in Mplayer top is showing 46%
> > 2. Playing the above file under the internal video player is showing 46
> > to 49%.
> > 3. Playing the recorded stream in Mplayer seems to be a bit better but
> > slow frame rate, but It is showing a lot of video corruption. Also i'm
> > getting the error message "too many video packets in the buffer"
> > constantly, and Top shows 65% CPU.
> > 4. I saw a post where the stutter NVP prebuffer pause was a result of
> > poor Aeriel, and I think this might be an issue as I suspect that HD is
> > more critical to the quality of the downlink. ( no problems with SD TV
> > payback on my system). Will try and use a better downlead as soon as I
> > can rig it up.
> > 5. Has anyone got a BBC HD recording that is clean that I can download
> > to test the system with?
> Because you are trying to playback h.264, I don't think there are any hardware
> accelerators that you can buy at this point for linux. I think you're going to
> have to do everything in software. Just like that I'm trying to do. I can get
> away with using XvMC for now, but it's not my ideal solution, and it's not a
> solution that will work for you.
> I wonder if the developers can start threading the playback app somehow so it
> can start using more than one core. I don't want to even imagine how difficult
> that might be to pull off.
> mythtv-users mailing list
> mythtv-users at mythtv.org
The problem is that the BBC HD is encoded with MBAFF H264, currently
ffmpeg cannot decode it in realtime even with a very fast cpu.
Normal H264 is ok, it is MBAFF that causes the problem, it is a type
of interlacing that makes decoding very cpu intensive, support for it
was only recently added to ffmpeg so perhaps it may be optimised and
improve in the future.
Alan Nisota wrote a patch that allowed mythtv to use CoreAVC Codec to
decode H264, that is the only codec that can decode MBAFF in realtime,
but it is a windows product. His patch works wtih CoreAVC 1.1 which
does not support MBAFF, I had a email from him this morning, he might
try to get his patch working with CoreAVC 1.2, I believe that would
allow realtime playback of BBC HD.
For the moment the best you can do is record and transcode anything
you want to watch on BBC HD.
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