Re-mux WebM to MP4

[RyanJVR]

Hi,

I'm trying to use -c:v copy along the same lines as this post https://stackoverflow.com/a/60443156 but not having any luck.
trying to copy the video in a webm;codecs=h264 container to a mp4 one.

         const transcode = async (webcamData) => {
                const name = 'record.webm';
                message.innerHTML = 'Loading ffmpeg-core.js';
                await ffmpeg.isLoaded();

                message.innerHTML = 'Start transcoding';

                ffmpeg.FS('writeFile', name, await fetchFile(webcamData));
                //await ffmpeg.run('-i', name,  'output.mp4' );

                await ffmpeg.run('-i', name, '-c:v copy', 'output.mp4');

                message.innerHTML = 'Complete transcoding';

                const data = ffmpeg.FS('readFile', 'output.mp4');

                //const video = document.getElementById('output-video');
                const videoURL = URL.createObjectURL(new Blob([data.buffer], { type: 'video/mp4;codecs=h264' }));
                const a = document.createElement('a');
                a.style.display = 'none';
                a.href = videoURL;
                a.download = 'Recording';
                document.body.appendChild(a);
                a.click();
                setTimeout(() => {
                    document.body.removeChild(a);
                    window.URL.revokeObjectURL(videoURL);
                }, 100);
            }

I get the following errors "At least one output file must be specified" & "Uncaught (in promise) Error: ffmpeg.FS('readFile', 'output.mp4') error. Check if the path exists".

Appreciate any assistance

[CrypticSignal]

-c:v and copy need to be separate arguments. Change
await ffmpeg.run('-i', name, '-c:v copy', 'output.mp4')
to
await ffmpeg.run('-i', name, '-c:v', 'copy', 'output.mp4').

[RyanJVR]

Thank you so much that worked on my desktop browser now to try mobile.