[mythtv-users] cut HD-PVR content with audio/video sync issues

Nick Rout nick.rout at gmail.com
Fri Feb 19 03:42:10 UTC 2010

On Fri, Feb 19, 2010 at 12:16 PM, Doug Vaughan <r.d.vaughan at rogers.com> wrote:
> I have not tried Robert's script in a very, very long time. The only reason
> is that I do not trust the automated process to decide where the cuts should
> be and you cannot adjust the edits in a Avidemux project file at least with
> v2.4.x this may have changed in v2.5.x.
> As for Avidemux v2.5.x, just last week I tried Ubuntu's v2.5.1 deb, a v2.5.2
> deb and compiled 2.5.2 version from the Avidemux svn. All aborted trying to
> open a HDPVR mpg/AC3 recording. I posted the abort on the Avidemux forum but
> did not get a response. I would like to upgrade but right now I am sticking
> to my compiled version from late last November.
> I used to sometimes get audio out of sync. If the out of sync was consistent
> throughout the file I used mkvmerge GUI to make adjustments. Out of sync
> audio that happened somewhere after the beginning of the loss-less video was
> usually a reflection of some transmission error recorded on the original
> HDPVR mpg file.
> When I first got my HDPVR I could not channel change my STB so I recorded on
> a STB/PVR before using the HDPVR. Every time I had an HDPVR recoding issue I
> could trace it back to the source. One movie I recorded multiple times from
> my Cable company and it always had the same picture and sound errors in the
> same time locations.
> Over the last 12 months or so there has been both firm ware upgrades but
> also a number of improvements on the Linux side (driver and MythTV). So I
> rarely see audio out of sync any more.
> I may give Roberts script another shot and adjust the commercial cuts within
> MythTV itself. I just had gotten very used to the manual process.
> I thought I read that your audio goes out of sync gradually. If true then
> try an experiment.
> 1) Use the script's avidemux project file but change the output container to
> be avi rather than mkv
> 2) Then process the resulting avi file through ffmpeg or mkvmerge to see if
> the final mkv file maintains audio sync.

I read a thread on the mythbuntu forum during this week that was about
hdpvr audio sync. Here is what was written in conclusion:

"The audio delay actually gets worse as time goes on. At the
beginning, it seems ok and then after a few minutes, you start to
notice a change...or drift. So, using that key word, I searched around
and found some people were also referring to this as "drift". Using
the right word makes all the difference in your searching.

People were noticing that the video was recording at 60fps rather than
59.94 (like the audio). Sure enough, so was mine. Using MediaInfo, I
was able to easily confirm this.

I had installed the most recent driver/firmware (in windows).
Hauppauge calls it a driver, but it is actually both. This was
supposed to fix the problem, but obviously had not. I called Hauppauge
to inquire about it. I asked if there was a way to confirm that the
firmware actually "took". They said no. How dumb is that? So, I
re-installed the firmware/driver in windows. It said that everything
went fine. I put it back on my Myth box and it still had the same

Next, I hunted down an old driver/firmware and installed that. Blammo,
it worked. My videos were 59.94fps! I went back (just for giggles) and
re-installed (for the 3rd time) the newest firmware/driver and it
continued to record videos at 59.94fps.

So, either the new firmware simply won't take on my unit and I'm on
the old firmware....or putting an old firmware on the box and then
trying the new firmware again worked...?

But, there is NO WAY to tell what firmware you have on the box. Dumb dumb dumb.

I do know that older firmware can be a little problematic. The box can
freeze up and Linux can even sometimes loose the device...i.e. you
need to unplug the USB and plug it back in.

So far, I have not had that problem, so I suspect that the new
firmware did take."

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