[vlc-devel] Audio transcoding/ASF mmsh Streaming WMP compatibility issue, current subversion

Mark Moriarty mfmbusiness at earthlink.net
Fri Jan 21 00:07:25 CET 2005

I placed a file, shaunclip2.mp4 on my ftp.  It was encoded as 128 kbps mp4v,
96K/channel mpga.  The clip is a bit over 6 MB.

Using a current subversion VLC build, built by me on 1/20 at 10:00 EST.  It
includes asf.c 9792 2005-01-20 14:30:17Z

If I use:
vlc shaunclip.mp4

The resulting stream is OK for a WMP10 connection

If I instead use:
vlc shaunclip.mp4

(the only change is ab=64)
WMP10 generates a CODEC message after the initial buffering:
"An audio codec is needed to play this file. To determine if this codec is
available to download from the Web, click Web Help."
It cannot find any CODEC, doesn't play the video.

A similar problem arises using a raw Directshow audio input.  If I stream it
using mp3 ab=96, the audio gets through to WMP10.  If I try ab=64 I get the
audio codec message.

Finally, if I start with a video that was originally encoded with 96K mp3,
it does work OK doing a transcode to 64K/channel mp3.  In other words:
Vlc afile_with_96k_mp3.asf

The above will successfully output a stream with 64K mp3 to WMP10.

Also, there is currently a general WMP incompatibility.  The above only
holds for WMP10 -- in WMP9 the 96K mp3 will also not play properly, will
generate a missing codec error.

I cannot tell if the two things are directly related or if there are
separate problems (audio transcoding and ASF muxing)


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