Error using ffmpeg to convert flv video

I am trying to convert flv video to mp4 using ffmpeg.

I have checked questions about converting from flv like this one and this one but it didn’t help.

Commands I have executed:

ffmpeg -i input.flv -c:v libx264 output.mp4

also:

ffmpeg -i input.flv -c:v libx264 -crf 19 -strict experimental output.mp4

also:

ffmpeg -i input.flv -codec copy output.mp4

also:

ffmpeg -i input.flv -c copy -copyts output.mp4

also:

ffmpeg -i input.flv -vcodec libvpx -acodec libvorbis output.mp4

I get below error from all above variants:

[flv @ 0xaaab0f4ec060] Packet mismatch 1703445535 198421 198574

[flv @0xaaab0f4ec060] Could not find codec parameters for stream 0 (Video:
h264, none): unspecified size Consider increasing the value for the
‘analyzeduration’ (0) and ‘probesize’ (5000000) options

Input #0, flv, from ‘input.flv’: Duration: 00:00:07.12, start: 0.000000, bitrate:
16070 kb/s Stream #0:0: Video: h264, none, 1k tbr, 1k tbn

Output #0, mp4, to ‘output.mp4’: Output file #0 does not contain any stream

Please note that I cannot reproduce the video using vlc. I managed to reproduce the video after downloading FLV-Media-Player

I think my video needs some kind of pre-processing but have no idea how to go about this.