#8523: ffmpeg converts 30fps input to 29.97fps when converting to .mxf
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Reporter: reakon | Owner:
Type: defect | Status: open
Priority: normal | Component: avformat
Version: git-master | Resolution:
Keywords: mxf | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by Tjoppen):
The problem is that we can't define mxf_spf for every conceivable
framerate. At the moment it is defined thus:
{{{
static const MXFSamplesPerFrame mxf_spf[] = {
{ { 1001, 24000 }, { 2002, 0, 0, 0, 0, 0 } }, // FILM
23.976
{ { 1, 24}, { 2000, 0, 0, 0, 0, 0 } }, // FILM 24
{ { 1001, 30000 }, { 1602, 1601, 1602, 1601, 1602, 0 } }, // NTSC
29.97
{ { 1, 30 }, { 1600, 0, 0, 0, 0, 0 } }, // 30
{ { 1001, 60000 }, { 801, 801, 800, 801, 801, 0 } }, // NTSC
59.94
{ { 1, 25 }, { 1920, 0, 0, 0, 0, 0 } }, // PAL 25
{ { 1, 50 }, { 960, 0, 0, 0, 0, 0 } }, // PAL 50
{ { 1, 60 }, { 800, 0, 0, 0, 0, 0 } },
};
}}}
mxf_content_package_rates relates to this as well:
{{{
static const int mxf_content_package_rates[] = {
3, 2, 7, 13, 4, 10, 12,
};
}}}
The muxer even warns about the inexact match:
>[mxf @ 00000187ba421d80] 1/30 input time base matched 1001/30000
container time base
IMO the muxer should outright refuse if the user isn't specifying *exacly*
the right time base, to avoid outputting things that will lose sync. With
MXF being picky is a necessity.
It might be possible to add support for specific rates without too much
engineering effort, but a general solution that also respects mxf_spf
would be trickier. Of course, audio-only MXF or .wav could be a solution
for Pro Tools
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8523#comment:7>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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