Better handling of "non-monotonically increasing dts to muxer" errors

[jailuthra]

Transcoding fails semi-frequently with:

[mpegts @ 0x7f277c4fb880] Application provided invalid, non monotonically increasing dts to muxer in stream 1: 181812 >= 181812
ERROR: transcoder.c:267] Error encoding : Invalid argument

TODO:

• [x] Find root-cause

This is caused by bad source video with messed up timestamps, causing the MPEGTS muxer to fail https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/mux.c#L602 and return EINVAL ("Invalid argument")

• [ ] Improve logs around it

The logging around this is confusing and not very descriptive. EINVAL could come from various sources.

• [ ] Fix it/handle it better

Dig deeper if we can handle the frame[n].pts == frame[n+1].pts case better to avoid these failures.