[mythtv-users] "NVP: prebuffering pause" "NVP::AddAudioData():p2: Audio buffer overflow, audio data lost!" "WriteAudio: buffer underrun"

[Michael T. Dean]

On 10/13/2008 07:53 PM, José Tomás @ Chico wrote:

> Michael T. Dean wrote:
> 
>> On 10/13/2008 02:45 PM, José Tomás @ Chico wrote:
>> 
>>> I'm having this issue for some channels of poor signal quality. 
>>> So lot's of messages in log saying that: "NVP: prebuffering 
>>> pause" or even sometimes during channel change 
>>> "NVP::AddAudioData():p2: Audio buffer overflow, audio data lost!"
>>>  plus "WriteAudio: buffer underrun"
>>> 
>>> Regarding what I found googling this is an old issue, but in 
>>> those posts I didn't found the solution. Post more then 1 year 
>>> old. It's like mythtv is not synchronizing correctly the signal.
>>> 
>>> Do you know anything about?
>>> 
>>> My TV singal is standard cable, not digital.
>> 
>> http://www.mythtv.org/wiki/index.php/Prebuffering_pause and, if 
>> yours isn't there, when you figure it out, please update the page 
>> with another cause/solution.
> 
> Good! I didn't found read that page.
> 
> Nevertheless the issue stands. I made a new DB, so everything fresh 
> and configured taking care the recommendations. What I did noticed is
>  if select on of those channels where I get no image, the issue 
> happens.
> 
> If I get out of Watch TV and then get back, about 5 sec after getting
> out, I'm able to see the channel correctly. These channels have the
> worst quality among the others.
> 
> What can these show?

Well, if you have poor signal quality, it may result in corrupt
recordings (it does for digital capture, but I have no idea how your
capture card/encoder will handle it for analog signals).  I would assume
that poor signal on an analog capture card would simply result in
static/noise which would be encoded into a valid video stream, meaning
that the recording itself would not be corrupt.

If your recording is /not/ corrupt, you may just need to enable the setting:

Extra audio buffering
Enable this setting if MythTV is playing "crackly" audio and you are
using hardware encoding. This setting will have no effect on MPEG-4 or
RTJPEG video. MythTV will keep extra audio data in its internal buffers
to workaround this bug.

(which is enabled by default and should never be disabled, so please
ensure it's enabled on yours).

If, however, you have corrupt recordings, you may have a problem.
TTBOMK, there's nothing you can do to "fix" Myth's playback of
corrupt/broken recordings.  If your signal issues are causing your
recordings to be corrupt, you really need to fix the signal quality
issue, which is something I'm trying to do myself, as signal quality for
nearly all my local over-the-air digital channels has dropped
significantly--from nearly perfect reception with no bit errors for
almost 2 years to just usable--within the last 6 months.  I'm just
hoping I find a better solution than the "ultimate" solution--which is
to stop using the channel.

Good luck,
Mike