This will stream copy (re-mux) all streams:

ffmpeg -i input -map 0 -c copy output.mp4

• If your inputs formats are not compatible with MP4 you will get an error.
• Your player/device may not support all arbitrary, less common, or legacy formats even if they are supported by MP4.
• If in doubt re-encode to H.264 + AAC as shown below.

This will re-encode the video to H.264 and stream copy the audio:

ffmpeg -i input.ts -c:v libx264 -c:a copy output.mp4

The next example will re-encode both video and audio:

ffmpeg -i input.ts -c:v libx264 -c:a aac output.mp4

Lossless H.264 example:

ffmpeg -i input.ts -c:v libx264 -crf 0 -c:a copy output.mp4

See FFmpeg Wiki: H.264 for more info.