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Problem Playing ATSC Recordings from CBS

 

 

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patrickkirchner at yahoo

Dec 29, 2009, 9:22 AM

Post #1 of 2 (423 views)
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Problem Playing ATSC Recordings from CBS

Hello,

Recordings from my local CBS station are problematic. I've investigated the files and they seem to be bit strange. SiliconDust tech support states that they are just "odd" in a normal way. I reported the issue to SiliconDust and this is what they had to say:

"The clip plays fine in everything I can try it in. The only slightly out of the ordinary thing I can see is that the station is using long GOPs to try to compensate for the low bitrate used, which can mean up to a 1 second delay before any video can start to be decoded. Most stations use 1/2 second GOPs, but up to 2-3 seconds isn't unheard of."

Here's the first 100MB of one of the recordings:

http://www.perdignus.com/100MB-of-CBS.mpg

When I play it with MythTV , it starts very jerky/choppy/no-audio and the only way I can get stop the jerky/choppy/no-audio is by changing the time stretch to something other than 0, then back to 0 again.

When I examine the file using mplayer with the -identify flag, I see odd stuff for the first 10564 lines and only starts playing after 10721 lines of stuff like this:

ID_VIDEO_ID=49
ID_VIDEO_ID=49
ID_VIDEO_ID=49
ID_VIDEO_ID=49
ID_VIDEO_ID=49
ID_VIDEO_ID=49


Here's the full text of "mplayer -vo null -ao null -identify:
http://www.perdignus.com/CBS-File.txt

I can play the recordings successfully with all other media players, just not in MythTV unless I change the time-stretch back and forth after starting the program.

I'm running Trunk and have had the issue months before the office release of .22. I've done clean installs of Linux, even moving from Ubuntu to Debian and the problem still exists. My box is a quad-core Intel with a GeForce 8800 GT. I've tried a number of playback profiles all to no avail.

If anyone could offer me some insight into this I'd appreciate it greatly.

Thanks,
Patrick



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dlinvill at networksdown

Dec 29, 2009, 3:10 PM

Post #2 of 2 (396 views)
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Re: Problem Playing ATSC Recordings from CBS [In reply to]

On Tue, Dec 29, 2009 at 11:22 AM, Patrick Kirchner <
patrickkirchner [at] yahoo> wrote:

> When I play it with MythTV , it starts very jerky/choppy/no-audio and the
> only way I can get stop the jerky/choppy/no-audio is by changing the time
> stretch to something other than 0, then back to 0 again.
>
>
That sounds like an audio thing. I think when you add time stretch it
switches from 5.1 to stereo in order to do the speedup magic and stays
stereo even when you go back to 0 time stretch. I can see the audio change
from 5.1 on my receiver and not go back.

I guess that doesn't help you much but explains the time stretch mystery.

David

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