[mythtv-users] HDTV Patch Feedback

[Daniel Thor Kristjansson]

Thanks for the feedback. It helps me to know what problems others
are having.

]> Now hdtv recordings playback almost flawlessly.
]> During a one hour show I might have only 2 or 3 little
]> "glitches".  These glitches might have a small
]> checkerboard pattern for just half a second.  When I
]> skip ahead or back, the audio and video stutter until
]> the OSD has faded.  When the camera pans fast I
]> sometimes see wavy artifacts.  This seems to be more
]> apparent on 1080i material (CBS) than 720p material
]> (NBC).  I'm running about 35% cpu utilization.  This
]> is great, this is more than useable for me.

The checkerboard pattern is probably due to bad packets in the
stream. The wavy artifacts are due to subsampling of an interlaced
stream, this should only happen with interlaced material. If it's
happening with 720p at all it was transmitted that way. This might
happen if the material was interlaced and then up-converted to 720p.

]> When I tune to a digital channel that isnt showing
]> 16:9 HDTV material, I have audio glitches.  This would
]> be a 4:3 screen inside the 16:9 window (like TV news
]> or a talk show, any non-HD material).  The audio has
]> terrible stutters.  This stuttering occurs on PBS,
]> ABC, CBS, UPN, and Fox.  The stuttering does not occur
]> on the WB and NBC.  Both the WB and NBC channel are
]> owned by the same company and broadcast from the same
]> tower.  This stuttering does not occur on HD material.
]>  Mythfrontend and backend give no errors.  When run in
]> verbose mode, mythfrontend says "Audio thread waiting
]> for buffer to fill fragment_size=4096, audiolen=4096".

Whether the material is HD or not isn't the problem. It
because of how the audio is transmitted. I don't have a
solution for this at the moment. But I do have a patch in
the works that will print out the Audio descriptor in the
PMT and hopefully let someone more knowledgable about A/V
syncing debug this problem.

]> Live TV has some issues.  The OSD seems to really
]> botch up playback on live streams.  If I go directly
]> to "Watch TV" it pops up the picure and everything is
]> fine (because it never brings up the OSD).  If I
]> change channels the OSD come ups and everything starts
]> to stutter and slow.  Sometimes it doesnt ever catch
]> up and the frontend crashes or just displays a picture
]> at 1 frame per second.  Even when the OSD disappears,
]> it won't "catch".

John Poet has this problem too. I get stuttering when the OSD is
fading, but it goes away after the OSD goes away. So my next approach
to this will be to allow turning off fading for OSD. But frame skipping
while the OSD is up might be better. A set of workarounds is currently
available however. 1) Hit esc right after you are done with the OSD,
this will make it go away earlier. 2) Hit p wait a second and then hit p
again followed by esc if the stutter doesn't go away, this will let the
decoder catch up.

]> The hdtv-recorder-v7 patch did not work at all for me.
]>  Whenever I tried to record something from Fox or PBS
]> mythbackend seg faulted immediately.  V6 does not
]> crash, and works great with my setup.

Well v7 is a debugging version. But if you had sent me the output of the
backend after the crash I could have probably fixed that bug. I'm
releasing v8 soon though, so just wait for that. It will decode more of
the ATSC and MPEG tables and some of the descriptors which will help in
figuring out some of the problems.

-- Daniel