void onLocalMediaClosed(String filePath)
If a broadcast is stopped before any data is produced, the library will not write anything and this callback will return null.
If finalization fails (for example if the storage is abruptly filled or external media is ejected), the library will leave a temporary file with video data you may be able to salvage.
filePath- Normally, the returned path equals the input to
storeLocalMedia(path, observer)but it may be null or a tmp-file.