> On 14 Sep 2020, at 13:54, <christian.w...@4-real.com>
> <christian.w...@4-real.com> wrote:
>
> Its all mono we are talking about here
>
> Full command line would be
> ffmpeg -nostats -i '#{filename}' -filter_complex ebur128 -f null - 2>&1
> (i only forward this from the IT section, but its the standard ffmpeg lufs
> measurment as far as i know)
>
> yes, we dont know if the customer values are correct. The problem is, there
> is no correct if you dont use the same method/algo.
> There are different meters coming up with different values on LUFSs,
> specially if you are under 0,4s.
> You are right, the best would be to use the same method, but our customer
> wont share their method and we cant reverse engineer something we dont own.
>
> Yes, there ist the (m) value in the output, but i think its not very reliable
> ... as the file measured isnt silent 😊
I would think M is not relevant, as it should equal I if the file is 400 Msecs…
And I can reproduce the issue on a short file. But, if I cat the file with
silence before / after, then measure with adding -ss yadda -t sourcedur it
seems to work.
(But a looped input results the same values when scanned fully.)
Bouke.
>
>
>
> -----Ursprüngliche Nachricht-----
> Von: ffmpeg-user <ffmpeg-user-boun...@ffmpeg.org> Im Auftrag von Bouke
> Gesendet: Montag, 14. September 2020 13:41
> An: FFmpeg user questions <ffmpeg-user@ffmpeg.org>
> Betreff: Re: [FFmpeg-user] LUFS measurment for short length audio
>
>
>> On 14 Sep 2020, at 13:23, christian.w...@4-real.com wrote:
>>
>>
>> To cat means to loop the file until it is longer then 0,4s?
>
> yes
>
>>
>> Yes we tried, there is a variation of 3db or more, so it is kind of
>> suboptimal.
>
> If it’s exact 3db, it smells like you might render the file to mono on
> catting, are you sure that’s not the case?
>
>> We also know the loudnorm command.
>
> Why, if you want to conform to R128 specs, you analyse, get the I value, and
> lower / up the volume by the measured Integrated minus target Integrated (in
> Db, one LU is equal to one dB)
>>
>> We use this command atm to read out values:
>>
>> ffmpeg -nostats -i 'filename' -filter_complex ebur128 -f null
>
> This might or might not work, if it’s 5.1, you would need to omit the LFE
> channel, and if there are multiple tracks you would need to patch the correct
> ones first.
> So, full command line / output missing :-) (I would never think I would write
> this…)
>
>> and it is fine with all files >0,4s. As it should be relating to the ebu128
>> definition.
>>
>> Anyway, our customer provides us with lufs values for shorter lenghts and he
>> wont tell us how he analyses it.
>
> So you have no clue if your client measurements are correct? I would not
> accept this, you would need to reverse engineer your clients steps...
>
>>
>> Now we tried to read out momentary lufs, as it works with 400ms windows, but
>> im not sure if i get correct values here.
>> As it shows -120db mLUFS for an example and on proTools it says
>> -23--24db (with DPMeterXP2)
>
> -120 is silence…
>
>>
>> Anybody an idea how to read out reliable momentary LUFS values with ffmpeg?
>
> Not sure how reliable it is, but it’s just in the output I would think…
>
> Bouke
>
>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: ffmpeg-user <ffmpeg-user-boun...@ffmpeg.org> Im Auftrag von Gyan
>> Doshi
>> Gesendet: Montag, 14. September 2020 09:50
>> An: ffmpeg-user@ffmpeg.org
>> Betreff: Re: [FFmpeg-user] LUFS measurment for short length audio
>>
>>
>>
>> On 14-09-2020 01:15 pm, Bouke wrote:
>>>> On 09 Sep 2020, at 10:33, christian.w...@4-real.com wrote:
>>>>
>>>>
>>>>
>>>> Hi list!
>>>>
>>>>
>>>>
>>>> Can somebody help to measure LUFS for audio files under 0,4 seconds???
>>>>
>>> Cat it a couple of times first?
>>
>> A few more times is required. Total duration should be >3 seconds.
>>
>> See https://superuser.com/q/1281327/
>>
>> Gyan
>> _______________________________________________
>>
>
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