[mythtv-users] A/V delay when recording HD

Geoffrey Schwartzreich atomik_kat at yahoo.com
Wed Oct 8 00:06:16 UTC 2008

I do think Comcast applies Dynamic-range compression on the audio of most
channels, or the feeds have it already.

TNTHD is awful about timecode problems. Sometimes it crashes my TiVo, and
files that I move from the TiVo and play back have numerous stream errors
and break VLC sometimes.

So, I think it's safe to say that Comcast or the upstream provider is
mucking around with the audio track or the timecoding is just overall
inaccurate on some feeds.


On 10/7/08 4:52 PM, "Florin Andrei" <florin at andrei.myip.org> wrote:

> Brad Fuller wrote:
>> AFA your captured stream: I assume you captured a QAM256 stream from
>> the coax since you are using HDHR.
> Well, forget the OP, explain my situation. :-)
> So yeah, it's a QAM256 (I *think* it's 256), recorded by MythTV from an
> HDHR tuner, from a regular Comcast cable feed. MPEG2 1080i. Upon
> analysis, the A and V tracks in the .mpg file turned out to be not
> aligned, there's an A/V timing difference slightly bigger than 1000ms.
> MythTV and pretty much any player is aware of the difference and the
> file is played in sync. So it looks like the timing diff is done on
> purpose by some component of the recording chain, and the whole thing is
> done properly.
> My question was - why are not A and V muxed in sync? Why there's a time
> delta at all? For some reason, I expected a file dumped from a broadcast
> feed to have A and V in sync, with a 0 ms difference in between.

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