[mythtv-users] Analog firewire recordings end early due to 25% fewer frames

[Tony Brummett]

On Wed, Feb 4, 2009 at 8:35 AM, Yeechang Lee <ylee at pobox.com> wrote:
> David Brodbeck <gull at gull.us> says:
>> If they're really being delivered to the cable box as analog signals,
>> they can't be chopping out frames.  Otherwise an analog TV would fail to
>> sync to them.  NTSC equipment is only designed to run at one frame
>> rate.
>
> I can't explain what I've seen for the past 15 months in any other
> way.

If the cable box _is_ actually using the analog video as the source,
then it must have some kind of MPEG encoder on-board in order to
deliver the video via firewire.  Because it's true, the analog NTSC
video must be 29.97 fps or a regular old TV wouldn't be able to
display the signal.  And if that's the case, then it's possible
there's a bug in that encoder, or that it's actually configured to
output at 22.48 fps (through I can't imagine why).

mplayer will show the framerate the video thinks it is, in the info it
prints before the video starts playing.  What does that say?  For one
of my videos recorded from a PVR250 it looks like:
VIDEO:  MPEG2  480x480  (aspect 2)  29.970 fps  6000.0 kbps (750.0 kbyte/s)

and for an ATSC recording
VIDEO:  MPEG2  1920x1080  (aspect 3)  29.970 fps  18900.0 kbps (2362.5 kbyte/s)

-- Tony