mock:// video_frame_rate option breaks the video stream

Without the option:

With the option: ./build-native/bin/vlc-osx-static 'mock://length=1000000000000000;video_width=1920;video_height=1080;video_track_count=1;audio_track_count=1;video_frame_rate=60'

The video and the PCR should not drift apart at the demuxer level.

changed milestone to %4.0

added Component::Test Type::bug labels

assigned to @alexandre-janniaux

No problem: fps = 50:

[0000600002f082a0] demux_mock access debug: Audio step length: 40,000000ms
[0000600002f082a0] demux_mock access debug: Video step length: 20,000000ms
[0000600002f082a0] demux_mock access debug: Video step length: 20,000000ms
[0000600002f082a0] demux_mock access debug: clock step length: 40,000000ms
```

Problem: fps = 60

```
[0000600000ded260] demux_mock access debug: clock step length: 40,000000ms
[0000600000ded260] demux_mock access debug: Audio step length: 40,000000ms
[0000600000ded260] demux_mock access debug: Video step length: 16,666000ms
[0000600000ded260] demux_mock access debug: Video step length: 16,666000ms
[0000600000ded260] demux_mock access debug: Video step length: 16,666000ms
[000000015b711800] main video output warning: picture is too late to be displayed (missing 21 ms)
[0000600000ded260] demux_mock access debug: clock step length: 40,000000ms
[0000600000ded260] demux_mock access debug: Audio step length: 40,000000ms
[0000600000ded260] demux_mock access debug: Video step length: 16,666000ms
[0000600000ded260] demux_mock access debug: Video step length: 16,666000ms
[0000600000ded260] demux_mock access debug: Video step length: 16,666000ms
```

At every demux call, the video will accumulate 8ms difference.

mentioned in merge request !7147 (merged)

closed with commit 7dad039d

closed with merge request !7147 (merged)