Conversion from WMV to MP4 file fails with FFmpeg

codec not currently supported in container

That's your error.

Try specifying another audio codec like with -c:a aac. MP4 doesn't take Windows Media Audio in its container. You have to choose a matching audio codec, like AAC. Right now all you do is try to copy the bitstream, and that fails – as indicated by the error message.

The same problem of non-matching codecs goes for other containers, although MKV is way more open to other codecs than MP4 is, therefore you can use almost any codecs within an MKV container. This does not work for MP4.

In general though, for maximum compatibility, try to stick to the most common formats for containers, e.g.

• AVI: MPEG-4 video, MP3 audio
• WMV: Windows Media Video and Audio
• MKV, MOV, MP4: h.264, AAC audio (although MKV really takes anything, here the limitation is on the playback device side)

try just doing:

ffmpeg -y -i 1.wmv -b:v 2000k 1.mp4

ffmpeg should automatically pick the most appropriate audio format and use libx264 for the video, the 2000k is essentially telling it to encode at the same bitrate as the original video file.