Error when adding srt file that contains two entries starting at the same moment

[rieve]

How to reproduce:

$ wget http://blender-mirror.kino3d.org/mango/download.blender.org/demo/movies/ToS/tears_of_steel_720p.mkv
[...]
$ ffmpeg -i tears_of_steel_720p.mkv -i tos.srt -map 1 -map 0 -c:v copy -c:a copy -c:s mov_text out.mp4
ffmpeg version N-68413-gd823ede Copyright (c) 2000-2014 the FFmpeg developers
[...]
Press [q] to stop, [?] for help
[mp4 @ 0x253dc40] Non-monotonous DTS in output stream 0:1; previous: -1333, current: -1333; changing to -1332. This may result in incorrect timestamps in the output file.
[mp4 @ 0x253dc40] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 2500 >= 2500
av_interleaved_write_frame(): Invalid argument
frame=   63 fps=0.0 q=-1.0 Lsize=      64kB time=00:00:02.69 bitrate= 194.9kbits/s    
video:7kB audio:53kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 6.905542%
Conversion failed!

[rieve]

srt file to reproduce with

[Cigaes]

Considering each subtitle replaces the previous one, what would you consider a reasonable behaviour? Silently dropping user input is not a good option.

[rieve]

Agreed. VLC displays all entries at the same time, that seems reasonable. So I'd suggest that the behaviour is equivalent to this:

1
00:00:02,500 --> 00:00:03,000
hello
world

2
00:00:03,000 --> 00:00:06,00
world