Whether a multimedia file will stream from Alfresco to your browser is determined by the format of the video or audio, whether your browser is HTML-5 compatible, and the version of the Flash plugin you have installed.
I tested a variety of audio and video formats on 4.2.c in two HTML-5 compatible browsers: Firefox and Chrome.
* I tried 3 mp3 files that were ripped in an identical manner. Only one played in the document previewer. All of them played when I clicked "View in Browser" using the browser media plugin. Alfresco correctly extracted the additional mp3 metadata from all of them. I don't understand what caused two to not play.
* ogg, flac, and m4a were not recognized by Alfresco as audio formats even though the MIME type was correctly set as an audio format. It did not extract any extra metada from ogg or flac, but did from the m4a.
* I tried 2 m4v files and both played in the previewer window. One had some corruption on Firefox that was not present in Chrome. They were both ripped in the same way, so I don't understand the difference. Alfresco did extract the additional metadata from the files.
* Alfresco recognized asf and wmv as video formats, but they didn't play in the preview window. It recognized ASF and WMV as Microsoft video format, bit didn't extract any extra metadata.
* Alfresco saw the mov file as a QuickTime video with extra metadata, and tries to play it in the previewer, but is unable to.
The preferred method of streaming for each file format is specified in the file web-extension/site-webscripts/org/alfresco/components/preview/web-preview.get.config.xml. I expect that file would be used to correctly identify the formats that are not currently being streamed, as well as to select a better player if your browser is HTML-5 but struggling with specific formats (perhaps one of the Flash media players would work better).
The key is to use formats that the browsers you are using can handle.
I reported my results to Engineering as ALF-17383.
