I have to produce an ASF format file that encodes ISO MPEG-4 video data (Microsoft codec with fourcc code MP4S or M4S2) and MP3 audio. I have tried Windows Media Encoder, which allows me to select the required video codec, but does not allow me to select an MP3 audio codec. Only WMA or PCM are available, even though I have an MP3 encoder installed.
I considered first encoding the file in another format (i.e. AVI), and converting to ASF using the vidtoasf utility, but all programs I have found allow me to encode using an MP3 codec, but not the required ISO MPEG-4 codec (I can use other MPEG4 codecs, but this is not what I require). I think the required Microsoft ISO MPEG-4 codec may be locked to only be used within ASF files. I have tried numerous conversion tools, but none would allow me to use the required video and audit codecs together - either directly in ASF format or in AVI which I can convert.
However I achieve this I need the end result of an ASF format file with the Microsoft ISO MPEG4 video codec and MP3 audio codec. Ideally I would do this with Windows Media Encoder, but I am open to other options.
Neither the file format (ASF) or specific codecs are negotiable, as the file is to be decoded on an embedded system that only supports these specific codecs and file format.