[mythtvnz] Commercial Flagging

[Steve V]

----- Original Message -----
> From: Tony Sauri <hoiho.nz at gmail.com>
> To: MythTV in NZ <mythtvnz at lists.linuxnut.co.nz>
> Cc: 
> Sent: Thursday, 18 August 2011 8:57 AM
> Subject: Re: [mythtvnz] Commercial Flagging
> 
> On Wed, 17 Aug 2011 22:15, Bruce Wilson wrote:
>>  maybe I have the wrong settings? I have set it to "all available 
> methods"
>> 
>>  On 17 August 2011 17:38, Nick Rout <nick.rout at gmail.com> wrote:
>>  > On Wed, Aug 17, 2011 at 5:24 PM, Bruce Wilson 
> <acaferacer at gmail.com>
>>  >
>>  > wrote:
>>  > > Hi,
>>  > > I have found the commercial flagging in MythTV does not work that
>>  > > great.
>>  >
>>  > Has
>>  >
>>  > > anyone done any work on optimising it for NZ?
>>  >
>>  > Always worked well for me.
>>  >
> 
> In common with others I have noticed very patch performance  ( I only receive 
> DVB-T programmes and cannot say whether my comments will also relate to DVB-S 
> recordings or capture from the back of a SKy Box)  Anywas I have been doing a 
> little bit of digging (code reading) to work out how the magic is done  and 
> try to understand what could be done to make things better.
> 
> There are three main methods provided:
>     black frame detection
>     scene change, and
>     logo detection
> 
> My comments:
>     I dont think any network in NZ consistently uses black frames before and
>     after every commercial break.
> 
>     Scene change does not seem to be a real starter
> 
>     Logo detection seems to be the technology most likely to work in NZ 
>     However as it works by edge-detection of the network logo it seems highly
>     dependent upon the intensity (and size ?) of the logo, so stations like
>     Prime and C4 with large and less transparent logos seem to have their ad
>     breaks more successfully detected than say One or Three. 
> 
>     There also seems to be a problem that if the first x mins of a recording are
>     only ads (because of pre-roll etc) then the detector decides there are no
>     logos and gives up.
> 
> Can we make the detector smarter to suit NZ?  I am not sure ... I have thought 
> of a few things but they are only tinkering around the edge and may introduce 
> more problems.
> 
> For now though because most ad breaks are some multiple of 30 secs I have a 30 
> sec forward skip  and a 10 sec backward skip on my remote so a few presses of 
> the button and were are back in business again!
> 
> Regards
> 
> Tony
> 
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I have heard from others that HD channels are more problematic for commercial flagging. It may be to do with the Logo detection as Tony has suggested or somethign to do with the amoutn of data that has to be processed.
I have always used only DVB-T reception for recording, a couple of years back commercial flagging worked very well on all channels perhaps about 90% reliability for me. Now I wonder if it was actually because back then only TVone was 1080 and all other channles were 720 or less and because I record very little from TVone I was seeing great results that were skewed toward channels transmitting in 720 or less.

With more channels on 1080, I find that commercial flagging is so unreliable that I no longer commercial flag any of my recordings and instead just use the 30 second skip forward button.


>