[FFmpeg-user] EBU R128 True Peak?

[Boštjan Strojan]

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?

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.