WAVE Splice: fractional framerate (14.985, 29.97, 59.94) CMAF Fragment duration considerations

[rbouqueau]

In my computations I considered an audio access unit duration of 1024 samples (i.e. 1024/48000 seconds).

With the constraint of CMAF Fragments alignment across audio 48khz and video Selection Sets:

• 25fps: 0.320s
• 30fps: 0.533...s
• 29.97fps: 21.25...s

I made the computation with 44.1khz audio for 29.97fps. My computed minimum duration is 3416.74...s. That doesn't seem usable but let me know if that's mandatory.

I suggest to use 2.133...s for 30fps (compatible with 15fps).

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As a trace, the computation consisted in finding two integer numbers so that AU_duration_audio * nb_AUs_audio = AU_duration_video * nb_AUs_video e.g. 1024/48000 * nb_AUs_audio = 1001/30000 * nb_AUs_video. That gave:

• 25 fps: 15 * nb_AUs_audio = 8 * nb_AUs_video : CMAF Fragment duration base = 1024/48000 * 15
• 30 fps: 1001 * nb_AUs_audio = 640 * nb_AUs_video : CMAF Fragment duration base = 1024/48000 * 1001
• 29.97 fps: 147147 * nb_AUs_audio = 102400 * nb_AUs_video : CMAF Fragment duration base = 1024/48000 * 147147

[nicholas-fr]

The mezzanine content has been generated, please see here for the details:
#18 (comment)