[mythtv-users] Running mythcommflag on another PC?

Ian Evans dheianevans at gmail.com
Wed Mar 6 19:38:52 UTC 2024


On Sun, Mar 3, 2024, 12:37 a.m. Ian Evans <dheianevans at gmail.com> wrote:

> On Sat, Mar 2, 2024 at 11:31 PM Ian Evans <dheianevans at gmail.com> wrote:
>
>>
>>
>> On Sat, Mar 2, 2024 at 7:02 PM Stephen Worthington <
>> stephen_agent at jsw.gen.nz> wrote:
>>
>>> As for mythcommflag performance, for processors 10 years old or
>>> younger and not the super cheap variety, then they can normally do
>>> commflagging on one recording per CPU core/thread in real time.  So
>>> for a 4 core dual threaded CPU, you could do 8 mythcommflag processes
>>> simultaneously in real time as 8 recordings happen together.  The
>>> trick with real time commflagging is that it gets done in RAM, on the
>>> buffered recording data before it gets written to disk.  Once the data
>>> has been written to disk, reading it back again slows down
>>> commflagging, as there is then the problem of contention for the disk,
>>> with the heads having to move between recordings.  So you also need
>>> enough RAM, as well as the CPU resources.
>>>
>>> I gave up doing commflagging a long time ago as here in New Zealand,
>>> it never gave useful results.  So I have not tried commflagging with
>>> the current generations of CPU, which are much faster again than 10
>>> year old ones.  They may well be able to do more than one mythcommflag
>>> operation per CPU thread, maybe even three or four.
>>>
>>> I would recommend a starting position of one commflag operation per
>>> CPU core/thread being run on the main recording box, starting the
>>> commflagging when the recording starts.  Then just let any more
>>> simultaneous recordings that go over that limit have their
>>> commflagging queued to be done later.  There should not be any need to
>>> have another box doing commflagging unless you are recording 20 things
>>> at once all day.
>>
>>
>> Just a quick background. My wife and I are currently working on another
>> place and I've just MacGyver'd a temporary setup so we'd have a PVR and I
>> could tiner with v34.
>>
>> The backend is currently running on an old Toshiba Satellite laptop. It
>> has 8 gig of RAM and a i7-3720QM CPU.
>>
>> According to Intel ARK:
>>
>>    - Total Cores 4
>>    - Total Threads 8
>>    - Max Turbo Frequency 3.60 GHz
>>    - Intel® Turbo Boost Technology 2.0 Frequency‡ 3.60 GHz
>>    - Processor Base Frequency 2.60 GHz
>>    - Cache 6 MB Intel® Smart Cache
>>
>>
>> When I tried running commercial detection a few months ago, I remember
>> the load spiking to 2.00. Can't remember if I had that running post
>> recording while there were other recordings. I may have not set it for
>> real-time detection thinking a laptop couldn't handle it. I'll have to
>> change the setup when my the SVU marathon is over.
>>
>
> An update. Went into setup and allowed commercial detection to start
> immediately. CPU setting was Low.
>
> Created a 15 minute manual recording a few minutes away and allowed
> commercial detection for that recording. The recording started.
>
> According to the queue it first looked up the metadata and then ran
> mythcommflag. According to top, load spiked to 3.97, and mythcommflag's CPU
> % was around 97%. During the whole 15 minutes of the recording it never got
> past "looking for logo:
>
> When the recording ended, it finally started processing. Load dropped down
> to about 1.75 and CPU% for mythcommflag was around 37%. According to the
> job queue it was running at about 97.0251 fps.
>
> Why would the logo detection spike so high?
>
>
What would you guys say is the minimum Intel/AMD generation for real-time
commercial flagging, because this i7-3720QM isn't cutting it.

Thanks.

>
>
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