[vdr] Re: vdr cuts recordings with ugly artifacts at cutting-points

[s.huelswitt@gmx.de (Stefan Huelswitt)]

On 16 Apr 2003 Oliver Endriss <o.endriss@gmx.de> wrote:
> Stefan Huelswitt wrote:
>> On 16 Apr 2003 "Dr. Werner Fink" <werner@suse.de> wrote:
>> > ... whats about the audio/dd frames between cutOut mark
>> > upto the point where the video PTS at cutOut reach the
>> > audio/dd PTS?  Shouldn't those ones be included or
>> > replaced with silence:
>> >
>> >                            commercial
>> >   video  ----------------%************%-----------------
>> >   audio  ----------------%--|*********%**|--------------
>> >                          ^            ^
>> >                        cutOut       cutIn
>> >                          ^^^^
>> >                          audio PTS delay
>> >
>> > ?
>>
>> Any packets behind cutOut are removed anyways (just as in plain
>> vdr). I can only guess that the driver will replace the missing
>> packets with silence.
>>
>> For a completely correct cut, these packets have to be recovered
>> and must be muxed into the packets after cutIn. This is not easy.
> 
> What about a simplified approach: Audio cutting could be based on the 
> PTS of the video, i.e.
> - delay audio cutOut until audio_PTS > video_PTS(CutOut)
> - delay audio cutIn until audio_PTS > video_PTS(cutIn)
> Maybe this would work *without* remuxing.

The current patch only does the second one.

I think, the first one cannot work without muxing.
I done as you suggested, we will end with a sequence like this:

VVVAVVAVVVA%AAA%VVVVVVVVVVAVVAVVAVVA

           ^   ^
           |   |
      cutOut   cutIn

Before the cutOut is the original muxed stream. After the cutOut,
all audio packets according to rule 1 follow. After the cutIn, we
have only video packets (according to rule 2).

Don't know if the decoder can buffer up so much audio packets. I
think the audio packets between the cutting points have to be
muxed with the video packets following the cutIn.

> Silence is bad[tm]. With the old solution, you could very often find a 
> good cutting point, because some channels repeat a some seconds of a 
> movie after the commercial break. If you simply discard audio frames 
> this will not work anymore.

I'm not sure if this really worked, as the PTS of the (exccess) audio
packets after the cutIn doesn't match the PTS of the video
packets before the cutOut.

-- 
Stefan Huelswitt
huels@iname.com  | http://home.pages.de/~nathan


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