[FFmpeg-user] EBU R128 True Peak?

[Manu N]

Hi again,


2013/4/25 Boštjan Strojan <bostjan.strojan at gmail.com>

> On Wed, Apr 24, 2013 at 7:02 PM, Manu N <audionuma at gmail.com> wrote:
>
> >> You have to keep in mind that the -1 dBTP limit is for PCM codecs. If
> your
> > stream is to go thru lossy codecs, you should keep within a tighter
> limit,
> > like -3 dBTP.
> > So if there's a sort of warning, it should be a user setting more than a
> > hardcoded value.
> > Besides, depending on the sample format in a PCM stream (fixed vs float),
> > raising the file1 to the target level might induce irreversible artifact
> on
> > peaks (let's say you have a stream whose integrated loudness is -27 LUFS
> > and max true-peak -3 dBTP, the +4 dB gain will create peakings if you are
> > in 16 bits PCM).
>
> Thats interesting, but do you actually have such stream in existance
> or are you theoretically speaking? (Just did a quick scan on bunch of
> "close to -23 LUFS" files and "sample peak" is max -6 dB, so basically
> "true peak" would have to be 6 dB higher?
>
I have received non-theorical deliveries for a nationwide broadcaster that
present the following values (that's a 1H30' documentary, excellent
production sound, 5.1 mix, 24 bits PCM 48 kHz) :
Integrated Loudness : -27 LUFS
LRA : 23 LU
Max true-peak : -1.3 dBTP

And a true-peak can be more than 6 dB higher than sample-peak for a 48 kHz
sample rate on certain circumstances.

As I don't think that this list is the proper place for these r128 related
discussion, I will not follow on the list but feel free to send me a PM if
you want to discuss about it.


>
> example sample:
> documentary_trailer_short.wav
> pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, stereo, s16, 1536 kb/s - 25s
> 0ms
> -9.0            dB max volume
> -20.5           LUFS Integrated loudness (I)
> 2.7             LU Loudness Range (LRA)
> -2.5            dB correction
>
>  -16 ++             +             +              +             +
>   ++
>      +              +             +        *     +             +
>    +
>  -18 ++                             *      *   * *             *
>   ++
>           * **    *     *  *       **     * * * **      **   * *
>  -20 ++   ** ** ** *    ***** ***  * *    * * *   *     ** ** **  **
>   ++
>           *    *    ** *     ** ** * *    *  *    * *  *  *     * **
>  -22 ++   *           **        * **  ** *         *****         ** *
>    ++
>          *            *           **  * **                        * *  ** *
>  -24 ++ *                                                            * *
> *** ++
>        *                                                              **
> ***
>        *                                                               *
> ***
>  -26 ++*
>  * *++
>        *
>  * *
>  -28 ++*
>  *  *+
>        *
>  *  *
>  -30 ++*
>   *+
>        *
>   *
>  -32 ++*
>   *+
>        *
>   *
>  -34 ++*            +             +              +             +
>   *+
>      + *            +             +              +             +
>   *+
>      0              5             10             15            20
>     25
>
> Y Momentary Loudness (min=-35, max=auto dB) / X Time in seconds
>
> B.
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>

Manuel