demux_lavf: get total duration from track durations

Before this change, mpv used to get the total duration from
`avformat_find_stream_info` and used the per-track duration as a
fallback. This change reverses this order of preference.

The timestamps returned by `avformat_find_stream_info` are truncated or
rounded or floored (depending on the decoder) at the 6th decimal place.
For e.g. `avformat_find_stream_info` may return us a duration like
44.138667, whereas the duration we get from the per-track struct has a
higher degree of precision like 44.13866666666... and so on.

This caused various problems such as the playback_pts being a bigger
value than the duration, which would cause time-remaining to be a
negative value in some cases. Or cause you to reach a negative starting
timestamp when looping on an audio file with `gapless-audio`.

Moreover, we already skipped calling `avformat_find_stream_info` for
mp4, so we had already been utilizing this per-track fallback method for
finding the duration for mp4 files. It should be noted that while this
change is only required for audio-only formats, there is no harm in
doing this for videos as well.

0 files changed, 0 insertions, 0 deletions